A mineral is a naturally occurring chemical compound,[1] usually of crystalline form and not produced by life processes. A  mineral has one specific chemical composition, whereas a rock can be an aggregate of different minerals or mineraloids. The study of minerals is called mineralogy.
Minerals are classified by variety, species, series and group, in order of increasing generality. As of November 2018, there are more than 5,500 known mineral species;[2] 5,389 of these have been approved by the International Mineralogical Association (IMA).[3]
Minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various species, which were determined by the mineral's geological environment when formed. Changes in the temperature, pressure, or bulk composition of a rock mass cause changes in its minerals. Within a mineral species there may be variation in physical properties or minor amounts of impurities that are recognized by mineralogists or wider society as a mineral variety,[4] for example amethyst, a purple variety of the mineral species quartz.
Minerals can be described by their various physical properties, which are related to their chemical structure and composition. Common distinguishing characteristics include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, tenacity, cleavage, fracture, parting, specific gravity, magnetism, taste or smell, radioactivity, and reaction to acid.
Minerals are classified by key chemical constituents; the two dominant systems are the Dana classification and the Strunz classification. Silicon and oxygen constitute approximately 75% of the Earth's crust, which translates directly into the predominance of silicate minerals. The silicate minerals compose over 90% of the Earth's crust.[5] The silicate class of minerals is subdivided into six subclasses by the degree of polymerization in the chemical structure. All silicate minerals have a base unit of a [SiO4]4− silica tetrahedron– that is, a silicon cation coordinated by four oxygen anions, which gives the shape of a tetrahedron. These tetrahedra can be polymerized to give the subclasses: orthosilicates (no polymerization, thus single tetrahedra), disilicates (two tetrahedra bonded together), cyclosilicates (rings of tetrahedra), inosilicates (chains of tetrahedra), phyllosilicates (sheets of tetrahedra), and tectosilicates (three-dimensional network of tetrahedra). Other important mineral groups include the native elements, sulfides, oxides, halides, carbonates, sulfates, and phosphates.

Definition
Basic definition
One definition of a mineral encompasses the following criteria:[6]
Formed by a natural process (anthropogenic compounds are excluded).
Stable or metastable at room  temperature (25°C). In the simplest sense, this means the mineral must be solid. Classical examples of exceptions to this rule include native mercury, which crystallizes at −39°C, and water ice, which is solid only below 0°C; because these two minerals were described before 1959, they were grandfathered by the International Mineralogical Association (IMA).[7][8] Modern advances have included extensive study of liquid crystals, which also extensively involve mineralogy.
Represented by a chemical formula. Minerals are chemical compounds, and as such they can be described by fixed or a variable formula. Many mineral groups and species are composed of a solid solution; pure substances are not usually found because of contamination or chemical substitution. For example, the olivine group is described by the variable formula (Mg, Fe)2SiO4, which is a solid solution of two end-member species, magnesium-rich forsterite and iron-rich fayalite, which are described by a fixed chemical formula. Mineral species themselves could have a variable composition, such as the sulfide mackinawite, (Fe, Ni)9S8, which is mostly a ferrous sulfide, but has a very significant nickel impurity that is reflected in its formula.[6][9]
Ordered atomic arrangement. This generally means crystalline; however, crystals are also periodic, so the broader criterion is used instead.[6] An ordered atomic arrangement gives rise to a variety of macroscopic physical properties, such as crystal form, hardness, and cleavage.[10] There have been several recent proposals to classify biogenic or amorphous substances as minerals. The formal definition of a mineral approved by the IMA in 1995: "A mineral is an element or chemical compound that is normally crystalline and that has been formed as a result of geological processes."[11]
Usually abiogenic (not resulting from the activity of living organisms). Biogenic substances are explicitly excluded by the IMA: "Biogenic substances are chemical compounds produced entirely by biological processes without a geological component (e.g., urinary calculi, oxalate crystals in plant tissues, shells of marine molluscs, etc.) and are not regarded as minerals. However, if geological processes were involved in the genesis of the compound, then the product can be accepted as a mineral."[11]
The first three general characteristics are less debated than the last two.[6]
Recent advances
Mineral classification schemes and their definitions are evolving to match recent advances in mineral science. Recent changes have included the addition of an organic class, in both the new Dana and the Strunz classification schemes.[12][13] The organic class includes a very rare group of minerals with hydrocarbons. The IMA Commission on New Minerals and Mineral Names adopted in 2009 a hierarchical scheme for the naming and classification of mineral groups and group names and established seven commissions and four working groups to review and classify minerals into an official listing of their published names.[14][15]  According to these new rules, "mineral species can be grouped in a number of different ways, on the basis of chemistry, crystal structure, occurrence, association, genetic history, or resource, for example, depending on the purpose to be served by the classification."[14]
The Nickel (1995) exclusion of biogenic substances was not universally adhered to. For example, Lowenstam (1981) stated that "organisms are capable of forming a diverse array of minerals, some of which cannot be formed inorganically in the biosphere."[16] The distinction is a matter of classification and less to do with the constituents of the minerals themselves. Skinner (2005) views all solids as potential minerals and includes biominerals in the mineral kingdom, which are those that are created by the metabolic activities of organisms. Skinner expanded the previous definition of a mineral to classify "element or compound, amorphous or crystalline, formed through biogeochemical  processes," as a mineral.[17]
Recent advances in high-resolution genetics and X-ray absorption spectroscopy are providing revelations on the biogeochemical relations between microorganisms and minerals that may make Nickel's (1995) biogenic mineral exclusion obsolete and Skinner's (2005) biogenic mineral inclusion a necessity.[11][17] For example, the IMA-commissioned "Working Group on Environmental Mineralogy and Geochemistry " deals with minerals in the hydrosphere, atmosphere, and biosphere.[18] The group's scope includes mineral-forming microorganisms, which exist on nearly every rock, soil, and particle surface spanning the globe to depths of at least 1600 metres below the sea floor and 70 kilometres into the stratosphere (possibly entering the mesosphere).[19][20][21] Biogeochemical cycles have contributed to the formation of minerals for billions of years. Microorganisms can precipitate metals from solution, contributing to the formation of ore deposits. They can also catalyze the dissolution of minerals.[22][23][24]
Prior to the International Mineralogical Association's listing, over 60 biominerals had been discovered, named, and published.[25] These minerals (a sub-set tabulated in Lowenstam (1981)[16]) are considered minerals proper according to the Skinner (2005) definition.[17] These biominerals are not listed in the International Mineral Association official list of mineral names,[26]  however, many of these biomineral representatives are distributed amongst the 78 mineral classes listed in the Dana classification scheme.[17] Another rare class of minerals (primarily biological in origin) include the mineral liquid crystals that have properties of both liquids and crystals. To date, over 80,000 liquid crystalline compounds have been identified.[27][28]
The Skinner (2005) definition of a mineral takes this matter into account by stating that a mineral can be crystalline or amorphous, the latter group including liquid crystals.[17] Although biominerals and liquid mineral crystals, are not the most common form of minerals,[29] they help to define the limits of what constitutes a mineral proper. The formal Nickel (1995) definition explicitly mentioned crystallinity as a key to defining a substance as a mineral. A 2011 article defined icosahedrite, an aluminium-iron-copper alloy as mineral; named for its unique natural icosahedral symmetry, it is a quasicrystal. Unlike a true crystal, quasicrystals are ordered but not periodic.[30][31]
Rocks, ores, and gems

Minerals are not equivalent to rocks. A rock is an aggregate of one or more minerals[32]  or mineraloids. Some rocks, such as limestone or quartzite, are composed primarily of one mineral– calcite or aragonite in the case of limestone, and quartz in the latter case.[33][34] Other rocks can be defined by relative abundances of key (essential) minerals; a granite is defined by proportions of quartz, alkali feldspar, and plagioclase feldspar.[35] The other minerals in the rock are termed accessory, and do not greatly affect the bulk composition of the rock. Rocks can also be composed entirely of non-mineral material; coal is a sedimentary rock composed primarily of organically derived carbon.[32][36]
In rocks, some mineral species and groups are much more abundant than others; these are termed the rock-forming minerals. The major examples of these are quartz, the feldspars, the micas, the amphiboles, the pyroxenes, the olivines, and calcite; except for the last one, all of these minerals are silicates.[37] Overall, around 150 minerals are considered particularly important, whether in terms of their abundance or aesthetic value in terms of collecting.[38]
Commercially valuable minerals and rocks are referred to as industrial minerals. For example, muscovite, a white mica, can be used for windows (sometimes referred to as isinglass), as a filler, or as an insulator.[39] Ores are minerals that have a high concentration of a certain element, typically a metal. Examples are cinnabar (HgS), an ore of mercury, sphalerite (ZnS), an ore of zinc, or cassiterite (SnO2), an ore of tin. Gems are minerals with an ornamental value, and are distinguished from non-gems by their beauty, durability, and usually, rarity. There are about 20 mineral species that qualify as gem minerals, which constitute about 35 of the most common gemstones. Gem minerals are often present in several varieties, and so one mineral can account for several different gemstones; for example, ruby and sapphire are both corundum, Al2O3.[40]
Nomenclature and classification
Minerals are classified by variety, species, series and group, in order of increasing generality. The basic level of definition is that of mineral species, each of which is distinguished from the others by unique chemical and physical properties. For example, quartz is defined by its formula, SiO2, and a specific crystalline structure that distinguishes it from other minerals with the same chemical formula (termed polymorphs). When there exists a range of composition between two minerals species, a mineral series is defined. For example, the biotite series is represented by variable amounts of the endmembers phlogopite, siderophyllite, annite, and eastonite. In contrast, a mineral group is a grouping of mineral species with some common chemical properties that share a crystal structure. The pyroxene group has a common  formula of XY(Si,Al)2O6, where X and Y are both cations, with X typically bigger than Y; the pyroxenes are single-chain silicates that crystallize in either the orthorhombic or monoclinic crystal systems. Finally, a mineral variety is a specific type of mineral species that differs by some physical characteristic, such as colour or crystal habit. An example is amethyst, which is a purple variety of quartz.[41]
Two common classifications, Dana and Strunz, are used for minerals; both rely on composition, specifically with regards to important chemical groups, and structure. James Dwight Dana, a leading geologist of his time, first published his System of Mineralogy in 1837; as of 1997, it is in its eighth edition. The Dana classification assigns a four-part number to a mineral species. Its class number is based on important compositional groups; the type gives the ratio of cations to anions in the mineral, and the last two numbers group minerals by structural similarity within a given type or class. The less commonly used Strunz classification, named for German mineralogist Karl Hugo Strunz, is based on the Dana system, but combines both chemical and structural criteria, the latter with regards to distribution of chemical bonds.[42]
As of November2018, 5,389 mineral species are approved by the IMA.[3] They are most commonly named after a person (45%), followed by discovery location (23%); names based on chemical composition (14%) and physical properties (8%) are the two other major groups of mineral name etymologies.[41][43]
The word "species" (from the Latin species, "a particular sort, kind, or type with distinct look, or appearance")[44] comes from the classification scheme in Systema Naturae by Carl Linnaeus. He divided the natural world into three kingdoms– plants, animals, and minerals– and classified each with the same hierarchy.[45] In descending order, these were Phylum, Class, Order, Family, Tribe, Genus, and Species.
Chemistry

The abundance and diversity of minerals is controlled directly by their chemistry, in turn dependent on elemental abundances in the Earth. The majority of minerals observed are derived from the Earth's crust. Eight elements account for most of the key components of minerals, due to their abundance in the crust. These eight elements, summing to over 98% of the crust by weight, are, in order of decreasing abundance: oxygen, silicon, aluminium, iron, magnesium, calcium, sodium and potassium. Oxygen and silicon are by far the two most important– oxygen composes 47% of the crust by weight, and silicon accounts for 28%.[46]
The minerals that form are directly controlled by the bulk chemistry of the parent body. For example, a magma rich in iron and magnesium will form mafic minerals, such as olivine and the pyroxenes; in contrast, a more silica-rich magma will crystallize to form minerals that incorporate more SiO2, such as the feldspars and quartz. In a limestone, calcite or aragonite (both CaCO3) form because the rock is rich in calcium and carbonate.  A corollary is that a mineral will not be found in a rock whose bulk chemistry does not resemble the bulk chemistry of a given mineral with the exception of trace minerals. For example, kyanite, Al2SiO5 forms from the metamorphism of aluminium-rich shales; it would not likely occur in aluminium-poor rock, such as quartzite.
The chemical composition may vary between end member species of a solid solution series. For example, the plagioclase feldspars comprise a continuous series from sodium-rich end member albite (NaAlSi3O8) to calcium-rich anorthite (CaAl2Si2O8) with four recognized intermediate varieties between them (given in order from sodium- to calcium-rich): oligoclase, andesine, labradorite, and bytownite.[47] Other examples of series include the olivine series of magnesium-rich forsterite and iron-rich fayalite, and the wolframite series of manganese-rich hübnerite and iron-rich ferberite.
Chemical substitution and coordination polyhedra explain this common feature of minerals. In nature, minerals are not pure substances, and are contaminated by whatever other elements are present in the given chemical system. As a result, it is possible for one element to be substituted for another.[48] Chemical substitution will occur between ions of a similar size and charge; for example, K+ will not substitute for Si4+ because of chemical and structural incompatibilities caused by a big difference in size and charge. A common example of chemical substitution is that of Si4+ by Al3+, which are close in charge, size, and abundance in the crust. In the example of plagioclase, there are three cases of substitution. Feldspars are all framework silicates, which have a silicon-oxygen ratio of 2:1, and the space for other elements is given by the substitution of Si4+ by Al3+ to give a base unit of [AlSi3O8]−; without the substitution, the formula would be charge-balanced as SiO2, giving quartz.[49] The significance of this structural property will be explained further by coordination polyhedra. The second substitution occurs between Na+ and Ca2+; however, the difference in charge has to accounted for by making a second substitution of Si4+ by Al3+.[50]
Coordination polyhedra are geometric representations of how a cation is surrounded by an anion. In mineralogy, coordination polyhedra are usually considered in terms of oxygen, due its abundance in the crust. The base unit of silicate minerals is the silica tetrahedron– one Si4+ surrounded by four O2−. An alternate way of describing the coordination of the silicate is by a number: in the case of the silica tetrahedron, the silicon is said to have a coordination number of 4. Various cations have a specific range of possible coordination numbers; for silicon, it is almost always 4, except for very high-pressure minerals where the compound is compressed such that silicon is in six-fold (octahedral) coordination with oxygen. Bigger cations have a bigger coordination numbers because of the increase in relative size as compared to oxygen (the last orbital subshell of heavier atoms is different too). Changes in coordination numbers leads to physical and mineralogical differences; for example, at high pressure, such as in the mantle, many minerals, especially silicates such as olivine and garnet, will change to a perovskite structure, where silicon is in octahedral coordination. Other examples are the aluminosilicates kyanite, andalusite, and sillimanite (polymorphs, since they share the formula Al2SiO5), which differ by the coordination number of the Al3+; these minerals transition from one another as a response to changes in pressure and temperature.[46] In the case of silicate materials, the substitution of Si4+ by Al3+ allows for a variety of minerals because of the need to balance charges.[51]

Changes in temperature and pressure and composition alter the mineralogy of a rock sample. Changes in composition can be caused by processes such as weathering or metasomatism (hydrothermal alteration). Changes in temperature and pressure occur when the host rock undergoes tectonic or magmatic movement into differing physical regimes. Changes in thermodynamic conditions make it favourable for mineral assemblages to react with each other to produce new minerals; as such, it is possible for two rocks to have an identical or a very similar bulk rock chemistry without having a similar mineralogy. This process of mineralogical alteration is related to the rock cycle. An example of a series of mineral reactions is illustrated as follows.[52]
Orthoclase feldspar (KAlSi3O8) is a mineral commonly found in granite, a plutonic igneous rock. When exposed to weathering, it reacts to form kaolinite (Al2Si2O5(OH)4, a sedimentary mineral, and silicic acid):
2 KAlSi3O8 + 5 H2O + 2 H+ → Al2Si2O5(OH)4 + 4 H2SiO3 + 2 K+
Under low-grade metamorphic conditions, kaolinite reacts with quartz to form pyrophyllite (Al2Si4O10(OH)2):
Al2Si2O5(OH)4 + SiO2 → Al2Si4O10(OH)2 + H2O
As metamorphic grade increases, the pyrophyllite reacts to form kyanite and quartz:
Al2Si4O10(OH)2 → Al2SiO5 + 3 SiO2 + H2O
Alternatively, a mineral may change its crystal structure as a consequence of changes in temperature and pressure without reacting. For example, quartz will change into a variety of its SiO2 polymorphs, such as tridymite and cristobalite at high temperatures, and coesite at high pressures.[53]
Physical properties
Classifying minerals ranges from simple to difficult. A mineral can be identified by several physical properties, some of them being sufficient for full identification without equivocation. In other cases, minerals can only be classified by more complex optical, chemical or X-ray diffraction analysis; these methods, however, can be costly and time-consuming.  Physical properties applied for classification include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, cleavage and fracture, and specific gravity. Other less general tests include fluorescence, phosphorescence, magnetism, radioactivity, tenacity (response to mechanical induced changes of shape or form), piezoelectricity and reactivity to dilute acids.[54]
Crystal structure and habit

Crystal structure results from the orderly geometric spatial arrangement of atoms in the internal structure of a mineral. This crystal structure is based on regular internal atomic or ionic arrangement that is often expressed in the geometric form that the crystal takes. Even when the mineral grains are too small to see or are irregularly shaped, the underlying crystal structure is always periodic and can be determined by X-ray diffraction.[6] Minerals are typically described by their symmetry content. Crystals are restricted to 32 point groups, which differ by their symmetry. These groups are classified in turn into more broad categories, the most encompassing of these being the six crystal families.[55]
These families can be described by the relative lengths of the three crystallographic axes, and the angles between them; these relationships correspond to the symmetry operations that define the narrower point groups. They are summarized below; a, b, and c represent the axes, and α, β, γ represent the angle opposite the respective crystallographic axis (e.g. α is the angle opposite the a-axis, viz. the angle between the b and c axes):[55]

The hexagonal crystal family is also split into two crystal systems– the trigonal, which has a three-fold axis of symmetry, and the hexagonal, which has a six-fold axis of symmetry.
Chemistry and crystal structure together define a mineral. With a restriction to 32 point groups, minerals of different chemistry may have identical crystal structure. For example, halite (NaCl), galena (PbS), and periclase (MgO) all belong to the hexaoctahedral point group (isometric family), as they have a similar stoichiometry between their different constituent elements. In contrast, polymorphs are groupings of minerals that share a chemical formula but have a different structure. For example, pyrite and marcasite, both iron sulfides, have the formula FeS2; however, the former is isometric while the latter is orthorhombic. This polymorphism extends to other sulfides with the generic AX2 formula; these two groups are collectively known as the pyrite and marcasite groups.[56]
Polymorphism can extend beyond pure symmetry content. The aluminosilicates are a group of three minerals– kyanite, andalusite, and sillimanite– which share the chemical formula Al2SiO5. Kyanite is triclinic, while andalusite and sillimanite are both orthorhombic and belong to the dipyramidal point group. These differences arise corresponding to how aluminium is coordinated within the crystal structure. In all minerals, one aluminium ion is always in six-fold coordination with oxygen. Silicon, as a general rule, is in four-fold coordination in all minerals; an exception is a case like stishovite (SiO2, an ultra-high pressure quartz polymorph with rutile structure).[57] In kyanite, the second aluminium is in six-fold coordination; its chemical formula can be expressed as Al[6]Al[6]SiO5, to reflect its crystal structure. Andalusite has the second aluminium in five-fold coordination (Al[6]Al[5]SiO5) and sillimanite has it in four-fold coordination (Al[6]Al[4]SiO5).[58]
Differences in crystal structure and chemistry greatly influence other physical properties of the mineral. The carbon allotropes diamond and graphite have vastly different properties; diamond is the hardest natural substance, has an adamantine lustre, and belongs to the isometric crystal family, whereas graphite is very soft, has a greasy lustre, and crystallises in the hexagonal family. This difference is accounted for by differences in bonding. In diamond, the carbons are in sp3 hybrid orbitals, which means they form a framework where each carbon is covalently bonded to four neighbours in a tetrahedral fashion; on the other hand, graphite is composed of sheets of carbons in sp2 hybrid orbitals, where each carbon is bonded covalently to only three others. These sheets are held together by much weaker van der Waals forces, and this discrepancy translates to large macroscopic differences.[59]

Twinning is the intergrowth of two or more crystals of a single mineral species. The geometry of the twinning is controlled by the mineral's symmetry. As a result, there are several types of twins, including contact twins, reticulated twins, geniculated twins, penetration twins, cyclic twins, and polysynthetic twins. Contact, or simple twins, consist of two crystals joined at a plane; this type of twinning is common in spinel. Reticulated twins, common in rutile, are interlocking crystals resembling netting. Geniculated twins have a bend in the middle that is caused by start of the twin. Penetration twins consist of two single crystals that have grown into each other; examples of this twinning include cross-shaped staurolite twins and Carlsbad twinning in orthoclase. Cyclic twins are caused by repeated twinning around a rotation axis. This type of twinning occurs around three, four, five, six, or eight-fold axes, and the corresponding patterns are called threelings, fourlings, fivelings, sixlings, and eightlings. Sixlings are common in aragonite. Polysynthetic twins are similar to cyclic twins through the presence of repetitive twinning; however, instead of occurring around a rotational axis, polysynthetic twinning occurs along parallel planes, usually on a microscopic scale.[60][61]
Crystal habit refers to the overall shape of crystal. Several terms are used to describe this property. Common habits include acicular, which describes needlelike crystals as in natrolite, bladed, dendritic (tree-pattern, common in native copper), equant, which is typical of garnet, prismatic (elongated in one direction), and tabular, which differs from bladed habit in that the former is platy whereas the latter has a defined elongation. Related to crystal form, the quality of crystal faces is diagnostic of some minerals, especially with a petrographic microscope. Euhedral crystals have a defined external shape, while anhedral crystals do not; those intermediate forms are termed subhedral.[62][63]
Hardness

The hardness of a mineral defines how much it can resist scratching. This physical property is controlled by the chemical composition and crystalline structure of a mineral. A mineral's hardness is not necessarily constant for all sides, which is a function of its structure; crystallographic weakness renders some directions softer than others.[64] An example of this property exists in kyanite, which has a Mohs hardness of 5½ parallel to [001] but 7 parallel to [100].[65]
The most common scale of measurement is the ordinal Mohs hardness scale. Defined by ten indicators, a mineral with a higher index scratches those below it. The scale ranges from talc, a phyllosilicate, to diamond, a carbon polymorph that is the hardest natural material. The scale is provided below:[64]

Lustre and diaphaneity

Lustre indicates how light reflects from the mineral's surface, with regards to its quality and intensity. There are numerous qualitative terms used to describe this property, which are split into metallic and non-metallic categories. Metallic and sub-metallic minerals have high reflectivity like metal; examples of minerals with this lustre are galena and pyrite. Non-metallic lustres include: adamantine, such as in diamond; vitreous, which is a glassy lustre very common in silicate minerals; pearly, such as in talc and apophyllite; resinous, such as members of the garnet group; silky which is common in fibrous minerals such as asbestiform chrysotile.[66]
The diaphaneity of a mineral describes the ability of light to pass through it. Transparent minerals do not diminish the intensity of light passing through them. An example of a transparent mineral is muscovite (potassium mica); some varieties are sufficiently clear to have been used for windows. Translucent minerals allow some light to pass, but less than those that are transparent. Jadeite and nephrite (mineral forms of jade are examples of minerals with this property). Minerals that do not allow light to pass are called opaque.[67][68]
The diaphaneity of a mineral depends on the thickness of the sample. When a mineral is sufficiently thin (e.g., in a thin section for petrography), it may become transparent even if that property is not seen in a hand sample. In contrast, some minerals, such as hematite or pyrite, are opaque even in thin-section.[68]
Colour and streak

Colour is the most obvious property of a mineral, but it is often non-diagnostic.[69] It is caused by electromagnetic radiation interacting with electrons (except in the case of incandescence, which does not apply to minerals).[70] Two broad classes of elements (idiochromatic and allochromatic) are defined with regards to their contribution to a mineral's colour: Idiochromatic elements are essential to a mineral's composition; their contribution to a mineral's colour is diagnostic.[67][71] Examples of such minerals are malachite (green) and azurite (blue). In contrast, allochromatic elements in minerals are present in trace amounts as impurities. An example of such a mineral would be the ruby and sapphire varieties of the mineral corundum.[71]
The colours of pseudochromatic minerals are the result of interference of light waves. Examples include labradorite and bornite.
In addition to simple body colour, minerals can have various other distinctive optical properties, such as play of colours, asterism, chatoyancy, iridescence, tarnish, and pleochroism. Several of these properties involve variability in colour. Play of colour, such as in opal, results in the sample reflecting different colours as it is turned, while pleochroism describes the change in colour as light passes through a mineral in a different orientation. Iridescence is a variety of the play of colours where light scatters off a coating on the surface of crystal, cleavage planes, or off layers having minor gradations in chemistry.[72] In contrast, the play of colours in opal is caused by light refracting from ordered microscopic silica spheres within its physical structure.[73] Chatoyancy ("cat's eye") is the wavy banding of colour that is observed as the sample is rotated; asterism, a variety of chatoyancy, gives the appearance of a star on the mineral grain. The latter property is particularly common in gem-quality corundum.[72][73]

The streak of a mineral refers to the colour of a mineral in powdered form, which may or may not be identical to its body colour.[71] The most common way of testing this property is done with a streak plate, which is made out of porcelain and coloured either white or black. The streak of a mineral is independent of trace elements[67] or any weathering surface.[71] A common example of this property is illustrated with hematite, which is coloured black, silver, or red in hand sample, but has a cherry-red[67] to reddish-brown streak.[71] Streak is more often distinctive for metallic minerals, in contrast to non-metallic minerals whose body colour is created by allochromatic elements.[67] Streak testing is constrained by the hardness of the mineral, as those harder than 7 powder the streak plate instead.[71]
Cleavage, parting, fracture, and tenacity

By definition, minerals have a characteristic atomic arrangement. Weakness in this crystalline structure causes planes of weakness, and the breakage of a mineral along such planes is termed cleavage. The quality of cleavage can be described based on how cleanly and easily the mineral breaks; common descriptors, in order of decreasing quality, are "perfect", "good", "distinct", and "poor". In particularly transparent minerals, or in thin-section, cleavage can be seen as a series of parallel lines marking the planar surfaces when viewed from the side. Cleavage is not a universal property among minerals; for example, quartz, consisting of extensively interconnected silica tetrahedra, does not have a crystallographic weakness which would allow it to cleave. In contrast, micas, which have perfect basal cleavage, consist of sheets of silica tetrahedra which are very weakly held together.[74][75]
As cleavage is a function of crystallography, there are a variety of cleavage types. Cleavage occurs typically in either one, two, three, four, or six directions. Basal cleavage in one direction is a distinctive property of the micas. Two-directional cleavage is described as prismatic, and occurs in minerals such as the amphiboles and pyroxenes. Minerals such as galena or halite have cubic (or isometric) cleavage in three directions, at 90°; when three directions of cleavage are present, but not at 90°, such as in calcite or rhodochrosite, it is termed rhombohedral cleavage. Octahedral cleavage (four directions) is present in fluorite and diamond, and sphalerite has six-directional dodecahedral cleavage.[74][75]
Minerals with many cleavages might not break equally well in all of the directions; for example, calcite has good cleavage in three directions, but gypsum has perfect cleavage in one direction, and poor cleavage in two other directions. Angles between cleavage planes vary between minerals. For example, as the amphiboles are double-chain silicates and the pyroxenes are single-chain silicates, the angle between their cleavage planes is different. The pyroxenes cleave in two directions at approximately 90°, whereas the amphiboles distinctively cleave in two directions separated by approximately 120° and 60°. The cleavage angles can be measured with a contact goniometer, which is similar to a protractor.[74][75]
Parting, sometimes called "false cleavage", is similar in appearance to cleavage but is instead produced by structural defects in the mineral, as opposed to systematic weakness. Parting varies from crystal to crystal of a mineral, whereas all crystals of a given mineral will cleave if the atomic structure allows for that property. In general, parting is caused by some stress applied to a crystal. The sources of the stresses include deformation (e.g. an increase in pressure), exsolution, or twinning. Minerals that often display parting include the pyroxenes, hematite, magnetite, and corundum.[74][76]
When a mineral is broken in a direction that does not correspond to a plane of cleavage, it is termed to have been fractured. There are several types of uneven fracture. The classic example is conchoidal fracture, like that of quartz; rounded surfaces are created, which are marked by smooth curved lines. This type of fracture occurs only in very homogeneous minerals. Other types of fracture are fibrous, splintery, and hackly. The latter describes a break along a rough, jagged surface; an example of this property is found in native copper.[77]
Tenacity is related to both cleavage and fracture. Whereas fracture and cleavage describes the surfaces that are created when a mineral is broken, tenacity describes how resistant a mineral is to such breaking. Minerals can be described as brittle, ductile, malleable, sectile, flexible, or elastic.[78]
Specific gravity

Specific gravity numerically describes the density of a mineral. The dimensions of density are mass divided by volume with units: kg/m3 or g/cm3. Specific gravity measures how much water a mineral sample displaces. Defined as the quotient of the mass of the sample and difference between the weight of the sample in air and its corresponding weight in water, specific gravity is a unitless ratio. Among most minerals, this property is not diagnostic. Rock forming minerals– typically silicates or occasionally carbonates– have a specific gravity of 2.5–3.5.[79]
High specific gravity is a diagnostic property of a mineral. A variation in chemistry (and consequently, mineral class) correlates to a change in specific gravity. Among more common minerals, oxides and sulfides tend to have a higher specific gravity as they include elements with higher atomic mass. A generalization is that minerals with metallic or adamantine lustre tend to have higher specific gravities than those having a non-metallic to dull lustre. For example, hematite, Fe2O3, has a specific gravity of 5.26[80] while galena, PbS, has a specific gravity of 7.2–7.6,[81] which is a result of their high iron and lead content, respectively. A very high specific gravity becomes very pronounced in native metals; kamacite, an iron-nickel alloy common in iron meteorites has a specific gravity of 7.9,[82] and gold has an observed specific gravity between 15 and 19.3.[79][83]
Other properties

Other properties can be used to diagnose minerals. These are less general, and apply to specific minerals.
Dropping dilute acid (often 10% HCl) onto a mineral aids in distinguishing carbonates from other mineral classes. The acid reacts with the carbonate ([CO3]2−) group, which causes the affected area to effervesce, giving off carbon dioxide gas. This test can be further expanded to test the mineral in its original crystal form or powdered form. An example of this test is done when distinguishing calcite from dolomite, especially within rocks (limestone and dolostone respectively). Calcite immediately effervesces in acid, whereas acid must be applied to powdered dolomite (often to a scratched surface in a rock), for it to effervesce.[84] Zeolite minerals will not effervesce in acid; instead, they become frosted after 5–10 minutes, and if left in acid for a day, they dissolve or become a silica gel.[85]
When tested, magnetism is a very conspicuous property of minerals. Among common minerals, magnetite exhibits this property strongly, and magnetism is also present, albeit not as strongly, in pyrrhotite and ilmenite.[84] Some minerals exhibit electrical properties – for example, quartz is piezoelectric – but electrical properties are rarely used as diagnostic criteria for minerals because of incomplete data and natural variation.[86]
Minerals can also be tested for taste or smell. Halite, NaCl, is table salt; its potassium-bearing counterpart, sylvite, has a pronounced bitter taste. Sulfides have a characteristic smell, especially as samples are fractured, reacting, or powdered.[84]
Radioactivity is a rare property; minerals may be composed of radioactive elements. They could be a defining constituent, such as uranium in uraninite, autunite, and carnotite, or as trace impurities. In the latter case, the decay of a radioactive element damages the mineral crystal; the result, termed a radioactive halo or pleochroic halo, is observable with various techniques, such as thin-section petrography.[84]
Classification
As the composition of the Earth's crust is dominated by silicon and oxygen, silicate elements are by far the most important class of minerals in terms of rock formation and diversity. However, non-silicate minerals are of great economic importance, especially as ores.[87][88]
Non-silicate minerals are subdivided into several other classes by their dominant chemistry, which includes native elements, sulfides, halides, oxides and hydroxides, carbonates and nitrates, borates, sulfates, phosphates, and organic compounds. Most non-silicate mineral species are rare (constituting in total 8% of the Earth's crust), although some are relatively common, such as calcite, pyrite, magnetite, and hematite. There are two major structural styles observed in non-silicates: close-packing and silicate-like linked tetrahedra. close-packed structures is a way to densely pack atoms while minimizing interstitial space. Hexagonal close-packing involves stacking layers where every other layer is the same ("ababab"), whereas cubic close-packing involves stacking groups of three layers ("abcabcabc"). Analogues to linked silica tetrahedra include SO4 (sulfate), PO4 (phosphate), AsO4 (arsenate), and VO4 (vanadate). The non-silicates have great economic importance, as they concentrate elements more than the silicate minerals do.[89]
The largest grouping of minerals by far are the silicates; most rocks are composed of greater than 95% silicate minerals, and over 90% of the Earth's crust is composed of these minerals.[90] The two main constituents of silicates are silicon and oxygen, which are the two most abundant elements in the Earth's crust. Other common elements in silicate minerals correspond to other common elements in the Earth's crust, such as aluminium, magnesium, iron, calcium, sodium, and potassium.[91] Some important rock-forming silicates include the feldspars, quartz, olivines, pyroxenes, amphiboles, garnets, and micas.
Silicates

The base unit of a silicate mineral is the [SiO4]4− tetrahedron. In the vast majority of cases, silicon is in four-fold or tetrahedral coordination with oxygen. In very high-pressure situations, silicon will be in six-fold or octahedral coordination, such as in the perovskite structure or the quartz polymorph stishovite (SiO2). In the latter case, the mineral no longer has a silicate structure, but that of rutile (TiO2), and its associated group, which are simple oxides. These silica tetrahedra are then polymerized to some degree to create various structures, such as one-dimensional chains, two-dimensional sheets, and three-dimensional frameworks. The basic silicate mineral where no polymerization of the tetrahedra has occurred requires other elements to balance out the base 4- charge. In other silicate structures, different combinations of elements are required to balance out the resultant negative charge. It is common for the Si4+ to be substituted by  Al3+ because of similarity in ionic radius and charge; in those cases, the [AlO4]5− tetrahedra form the same structures as do the unsubstituted tetrahedra, but their charge-balancing requirements are different.[92]
The degree of polymerization can be described by both the structure formed and how many tetrahedral corners (or coordinating oxygens) are shared (for aluminium and silicon in tetrahedral sites).[93] Orthosilicates (or nesosilicates) have no linking of polyhedra, thus tetrahedra share no corners. Disilicates (or sorosilicates) have two tetrahedra sharing one oxygen atom. Inosilicates are chain silicates; single-chain silicates have two shared corners, whereas double-chain silicates have two or three shared corners. In phyllosilicates, a sheet structure is formed which requires three shared oxygens; in the case of double-chain silicates, some tetrahedra must share two corners instead of three as otherwise a sheet structure would result. Framework silicates, or tectosilicates, have tetrahedra that share all four corners. The ring silicates, or cyclosilicates, only need tetrahedra to share two corners to form the cyclical structure.[94]
The silicate subclasses are described below in order of decreasing polymerization.
Tectosilicates

Tectosilicates, also known as framework silicates, have the highest degree of polymerization. With all corners of a tetrahedra shared, the silicon:oxygen ratio becomes 1:2. Examples are quartz, the feldspars, feldspathoids, and the zeolites. Framework silicates tend to be particularly chemically stable as a result of strong covalent bonds.[95]
Forming 12% of the Earth's crust, quartz (SiO2) is the most abundant mineral species. It is characterized by its high chemical and physical resistivity. Quartz has several polymorphs, including tridymite and cristobalite at high temperatures, high-pressure coesite, and ultra-high pressure stishovite. The latter mineral can only be formed on Earth by meteorite impacts, and its structure has been composed so much that it had changed from a silicate structure to that of rutile (TiO2). The silica polymorph that is most stable at the Earth's surface is α-quartz. Its counterpart, β-quartz, is present only at high temperatures and pressures (changes to α-quartz below 573°C at 1 bar). These two polymorphs differ by a "kinking" of bonds; this change in structure gives β-quartz greater symmetry than α-quartz, and they are thus also called high quartz (β) and low quartz (α).[90][96]
Feldspars are the most abundant group in the Earth's crust, at about 50%. In the feldspars, Al3+ substitutes for Si4+, which creates a charge imbalance that must be accounted for by the addition of cations. The base structure becomes either [AlSi3O8]− or [Al2Si2O8]2−  There are 22 mineral species of feldspars, subdivided into two major subgroups – alkali and plagioclase – and two less common groups – celsian and banalsite. The alkali feldspars are most commonly in a series between potassium-rich orthoclase and sodium-rich albite; in the case of plagioclase, the most common series ranges from albite to calcium-rich anorthite. Crystal twinning is common in feldspars, especially polysynthetic twins in plagioclase and Carlsbad twins in alkali feldspars. If the latter subgroup cools slowly from a melt, it forms exsolution lamellae because the two components – orthoclase and albite – are unstable in solid solution. Exsolution can be on a scale from microscopic to readily observable in hand-sample; perthitic texture forms when Na-rich feldspar exsolve in a K-rich host. The opposite texture (antiperthitic), where K-rich feldspar exsolves in a Na-rich host, is very rare.[97]
Feldspathoids are structurally similar to feldspar, but differ in that they form in Si-deficient conditions, which allows for further substitution by Al3+. As a result, feldspathoids cannot be associated with quartz. A common example of a feldspathoid is nepheline ((Na, K)AlSiO4); compared to alkali feldspar, nepheline has an Al2O3:SiO2 ratio of 1:2, as opposed to 1:6 in the feldspar.[98] Zeolites often have distinctive crystal habits, occurring in needles, plates, or blocky masses. They form in the presence of water at low temperatures and pressures, and have channels and voids in their structure. Zeolites have several industrial applications, especially in waste water treatment.[99]
Phyllosilicates

Phyllosilicates consist of sheets of polymerized tetrahedra. They are bound at three oxygen sites, which gives a characteristic silicon:oxygen ratio of 2:5. Important examples include the mica, chlorite, and the kaolinite-serpentine groups. The sheets are weakly bound by van der Waals forces or hydrogen bonds, which causes a crystallographic weakness, in turn leading to a prominent basal cleavage among the phyllosilicates.[100] In addition to the tetrahedra, phyllosilicates have a sheet of octahedra (elements in six-fold coordination by oxygen) that balance out the basic tetrahedra, which have a negative charge (e.g. [Si4O10]4−) These tetrahedra (T) and octahedra (O) sheets are stacked in a variety of combinations to create phyllosilicate groups. Within an octahedral sheet, there are three octahedral sites in a unit structure; however, not all of the sites may be occupied. In that case, the mineral is termed dioctahedral, whereas in other case it is termed trioctahedral.[101]
The kaolinite-serpentine group consists of T-O stacks (the 1:1 clay minerals); their hardness ranges from 2 to 4, as the sheets are held by hydrogen bonds. The 2:1 clay minerals (pyrophyllite-talc) consist of T-O-T stacks, but they are softer (hardness from 1 to 2), as they are instead held together by van der Waals forces. These two groups of minerals are subgrouped by octahedral occupation; specifically, kaolinite and pyrophyllite are dioctahedral whereas serpentine and talc trioctahedral.[102]
Micas are also T-O-T-stacked phyllosilicates, but differ from the other T-O-T and T-O-stacked subclass members in that they incorporate aluminium into the tetrahedral sheets (clay minerals have Al3+ in octahedral sites). Common examples of micas are muscovite, and the biotite series. The chlorite group is related to mica group, but a brucite-like (Mg(OH)2) layer between the T-O-T stacks.[103]
Because of their chemical structure, phyllosilicates typically have flexible, elastic, transparent layers that are electrical insulators and can be split into very thin flakes. Micas can be used in electronics as insulators, in construction, as optical filler, or even cosmetics. Chrysotile, a species of serpentine, is the most common mineral species in industrial asbestos, as it is less dangerous in terms of health than the amphibole asbestos.[104]
Inosilicates

Inosilicates consist of tetrahedra repeatedly bonded in chains. These chains can be single, where a tetrahedron is bound to two others to form a continuous chain; alternatively, two chains can be merged to create double-chain silicates. Single-chain silicates have a silicon:oxygen ratio of 1:3 (e.g. [Si2O6]4−), whereas the double-chain variety has a ratio of 4:11, e.g. [Si8O22]12−. Inosilicates contain two important rock-forming mineral groups; single-chain silicates are most commonly pyroxenes, while double-chain silicates are often amphiboles.[105] Higher-order chains exist (e.g. three-member, four-member, five-member chains, etc.) but they are rare.[106]
The pyroxene group consists of 21 mineral species.[107] Pyroxenes have a general structure formula of XY(Si2O6), where X is an octahedral site, while Y can vary in coordination number from six to eight. Most varieties of pyroxene consist of permutations of Ca2+, Fe2+ and Mg2+ to balance the negative charge on the backbone. Pyroxenes are common in the Earth's crust (about 10%) and are a key constituent of mafic igneous rocks.[108]
Amphiboles have great variability in chemistry, described variously as a "mineralogical garbage can" or a "mineralogical shark swimming a sea of elements". The backbone of the amphiboles is the [Si8O22]12−; it is balanced by cations in three possible positions, although the third position is not always used, and one element can occupy both remaining ones. Finally, the amphiboles are usually hydrated, that is, they have a hydroxyl group ([OH]−), although it can be replaced by a fluoride, a chloride, or an oxide ion.[109] Because of the variable chemistry, there are over 80 species of amphibole, although variations, as in the pyroxenes, most commonly involve mixtures of Ca2+, Fe2+ and Mg2+.[107] Several amphibole mineral species can have an asbestiform crystal habit. These asbestos minerals form long, thin, flexible, and strong fibres, which are electrical insulators, chemically inert and heat-resistant; as such, they have several applications, especially in construction materials. However, asbestos are known carcinogens, and cause various other illnesses, such as asbestosis; amphibole asbestos (anthophyllite, tremolite, actinolite, grunerite, and riebeckite) are considered more dangerous than chrysotile serpentine asbestos.[110]
Cyclosilicates

Cyclosilicates, or ring silicates, have a ratio of silicon to oxygen of 1:3. Six-member rings are most common, with a base structure of [Si6O18]12−; examples include the tourmaline group and beryl. Other ring structures exist, with 3, 4, 8, 9, 12 having been described.[111]  Cyclosilicates tend to be strong, with elongated, striated crystals.[112]
Tourmalines have a very complex chemistry that can be described by a general formula XY3Z6(BO3)3T6O18V3W. The T6O18 is the basic ring structure, where T is usually Si4+, but substitutable by Al3+ or B3+. Tourmalines can be subgrouped by the occupancy of the X site, and from there further subdivided by the chemistry of the W site. The Y and Z sites can accommodate a variety of cations, especially various transition metals; this variability in structural transition metal content gives the tourmaline group greater variability in colour. Other cyclosilicates include beryl, Al2Be3Si6O18, whose varieties include the gemstones emerald (green) and aquamarine (bluish). Cordierite is structurally similar to beryl, and is a common metamorphic mineral.[113]
Sorosilicates

Sorosilicates, also termed disilicates, have tetrahedron-tetrahedron bonding at one oxygen, which results in a 2:7 ratio of silicon to oxygen. The resultant common structural element is the [Si2O7]6− group. The most common disilicates by far are members of the epidote group. Epidotes are found in variety of geologic settings, ranging from mid-ocean ridge to granites to metapelites. Epidotes are built around the structure [(SiO4)(Si2O7)]10− structure; for example, the mineral species epidote has calcium, aluminium, and ferric iron to charge balance: Ca2Al2(Fe3+, Al)(SiO4)(Si2O7)O(OH). The presence of iron as Fe3+ and Fe2+ helps understand oxygen fugacity, which in turn is a significant factor in petrogenesis.[114]
Other examples of sorosilicates include lawsonite, a  metamorphic mineral forming in the blueschist facies (subduction zone setting with low temperature and high pressure), vesuvianite, which takes up a significant amount of calcium in its chemical structure.[114][115]
Orthosilicates

Orthosilicates consist of isolated tetrahedra that are charge-balanced by other cations.[116] Also termed nesosilicates, this type of silicate has a silicon:oxygen ratio of 1:4 (e.g. SiO4). Typical orthosilicates tend to form blocky equant crystals, and are fairly hard.[117] Several rock-forming minerals are part of this subclass, such as the aluminosilicates, the olivine group, and the garnet group.
The aluminosilicates –bkyanite, andalusite, and sillimanite, all Al2SiO5 – are structurally composed of one [SiO4]4− tetrahedron, and one Al3+ in octahedral coordination. The remaining Al3+ can be in six-fold coordination (kyanite), five-fold (andalusite) or four-fold (sillimanite); which mineral forms in a given environment is depend on pressure and temperature conditions. In the olivine structure, the main olivine series of (Mg, Fe)2SiO4 consist of magnesium-rich forsterite and iron-rich fayalite. Both iron and magnesium are in octahedral by oxygen. Other mineral species having this structure exist, such as tephroite, Mn2SiO4.[118] The garnet group has a general formula of X3Y2(SiO4)3, where X is a large eight-fold coordinated cation, and Y is a smaller six-fold coordinated cation. There are six ideal endmembers of garnet, split into two group. The pyralspite garnets have Al3+ in the Y position: pyrope (Mg3Al2(SiO4)3), almandine (Fe3Al2(SiO4)3), and spessartine (Mn3Al2(SiO4)3). The ugrandite garnets have Ca2+ in the X position: uvarovite (Ca3Cr2(SiO4)3), grossular (Ca3Al2(SiO4)3) and andradite (Ca3Fe2(SiO4)3). While there are two subgroups of garnet, solid solutions exist between all six end-members.[116]
Other orthosilicates include zircon, staurolite, and topaz. Zircon (ZrSiO4) is useful in geochronology as the Zr4+ can be substituted by U6+; furthermore, because of its very resistant structure, it is difficult to reset it as a chronometer. Staurolite is a common metamorphic intermediate-grade index mineral. It has a particularly complicated crystal structure that was only fully described in 1986. Topaz (Al2SiO4(F, OH)2, often found in granitic pegmatites associated with tourmaline, is a common gemstone mineral.[119]
Non-silicates
Native elements

Native elements are those that are not chemically bonded to other elements. This mineral group includes native metals, semi-metals, and non-metals, and various alloys and solid solutions. The metals are held together by metallic bonding, which confers distinctive physical properties such as their shiny metallic lustre, ductility and malleability, and electrical conductivity. Native elements are subdivided into groups by their structure or chemical attributes.
The gold group, with a cubic close-packed structure, includes metals such as gold, silver, and copper. The platinum group is similar in structure to the gold group. The iron-nickel group is characterized by several iron-nickel alloy species. Two examples are kamacite and taenite, which are found in iron meteorites; these species differ by the amount of Ni in the alloy; kamacite has less than 5–7% nickel and is a variety of native iron, whereas the nickel content of taenite ranges from 7–37%. Arsenic group minerals consist of semi-metals, which have only some metallic traits; for example, they lack the malleability of metals. Native carbon occurs in two allotropes, graphite and diamond; the latter forms at very high pressure in the mantle, which gives it a much stronger structure than graphite.[120]
Sulfides

The sulfide minerals are chemical compounds of one or more metals or semimetals with a sulfur; tellurium, arsenic, or selenium can substitute for the sulfur. Sulfides tend to be soft, brittle minerals with a high specific gravity. Many powdered sulfides, such as pyrite, have a sulfurous smell when powdered. Sulfides are susceptible to weathering, and many readily dissolve in water; these dissolved minerals can be later redeposited, which creates enriched secondary ore deposits.[121] Sulfides are classified by the ratio of the metal or semimetal to the sulfur, such as M:S equal to 2:1, or 1:1.[122] Many sulfide minerals are economically important as metal ores; examples include sphalerite (ZnS), an ore of zinc, galena (PbS), an ore of lead, cinnabar (HgS), an ore of mercury, and molybdenite (MoS2, an ore of molybdenum.[123] Pyrite (FeS2), is the most commonly occurring sulfide, and can be found in most geological environments. It is not, however, an ore of iron, but can be instead oxidized to produce sulfuric acid.[124] Related to the sulfides are the rare sulfosalts, in which a metallic element is bonded to sulfur and a semimetal such as antimony, arsenic, or bismuth. Like the sulfides, sulfosalts are typically soft, heavy, and brittle minerals.[125]
Oxides

Oxide minerals are divided into three categories: simple oxides, hydroxides, and multiple oxides. Simple oxides are characterized by O2− as the main anion and primarily ionic bonding. They can be further subdivided by the ratio of oxygen to the cations. The periclase group consists of minerals with a 1:1 ratio. Oxides with a 2:1 ratio include cuprite (Cu2O) and water ice. Corundum group minerals have a 2:3 ratio, and includes minerals such as corundum (Al2O3), and hematite (Fe2O3). Rutile group minerals have a ratio of 1:2; the eponymous species, rutile (TiO2) is the chief ore of titanium; other examples include cassiterite (SnO2; ore of tin), and pyrolusite (MnO2; ore of manganese).[126][127]  In hydroxides, the dominant anion is the hydroxyl ion, OH−. Bauxites are the chief aluminium ore, and are a heterogeneous mixture of the hydroxide minerals diaspore, gibbsite, and bohmite; they form in areas with a very high rate of chemical weathering (mainly tropical conditions).[128]  Finally, multiple oxides are compounds of two metals with oxygen. A major group within this class are the spinels, with a general formula of X2+Y3+2O4. Examples of species include spinel (MgAl2O4), chromite (FeCr2O4), and magnetite (Fe3O4). The latter is readily distinguishable by its strong magnetism, which occurs as it has iron in two oxidation states (Fe2+Fe3+2O4), which makes it a multiple oxide instead of a single oxide.[129]
Halides

The halide minerals are compounds in which a halogen (fluorine, chlorine, iodine, or bromine) is the main anion. These minerals tend to be soft, weak, brittle, and water-soluble. Common examples of halides include halite (NaCl, table salt), sylvite (KCl), fluorite (CaF2). Halite and sylvite commonly form as evaporites, and can be dominant minerals in chemical sedimentary rocks. Cryolite, Na3AlF6, is a key mineral in the extraction of aluminium from bauxites; however, as the only significant occurrence at Ivittuut, Greenland, in a granitic pegmatite, was depleted, synthetic cryolite can be made from fluorite.[130]
Carbonates

The carbonate minerals are those in which the main anionic group is carbonate, [CO3]2−. Carbonates tend to be brittle, many have rhombohedral cleavage, and all react with acid.[131] Due to the last characteristic, field geologists often carry dilute hydrochloric acid to distinguish carbonates from non-carbonates. The reaction of acid with carbonates, most commonly found as the polymorph calcite and aragonite (CaCO3), relates to the dissolution and precipitation of the mineral, which is a key in the formation of limestone caves, features within them such as stalactite and stalagmites, and karst landforms. Carbonates are most often formed as biogenic or chemical sediments in marine environments. The carbonate group is structurally a triangle, where a central C4+ cation is surrounded by three O2− anions; different groups of minerals form from different arrangements of these triangles.[132] The most common carbonate mineral is calcite, which is the primary constituent of sedimentary limestone and metamorphic marble. Calcite, CaCO3, can have a high magnesium impurity. Under high-Mg conditions, its polymorph aragonite will form instead; the marine geochemistry in this regard can be described as an aragonite or calcite sea, depending on which mineral preferentially forms. Dolomite is a double carbonate, with the formula CaMg(CO3)2. Secondary dolomitization of limestone is common, in which calcite or aragonite are converted to dolomite; this reaction increases pore space (the unit cell volume of dolomite is 88% that of calcite), which can create a reservoir for oil and gas. These two mineral species are members of eponymous mineral groups: the calcite group includes carbonates with the general formula XCO3, and the dolomite group constitutes minerals with the general formula XY(CO3)2.[133]
Sulfates

The sulfate minerals all contain the sulfate anion, [SO4]2−. They tend to be transparent to translucent, soft, and many are fragile.[134] Sulfate minerals commonly form as evaporites, where they precipitate out of evaporating saline waters. Sulfates can also be found in hydrothermal vein systems associated with sulfides,[135] or as oxidation products of sulfides.[136] Sulfates can be subdivided into anhydrous and hydrous minerals. The most common hydrous sulfate by far is gypsum, CaSO4⋅2H2O. It forms as an evaporite, and is associated with other evaporites such as calcite and halite; if it incorporates sand grains as it crystallizes, gypsum can form desert roses. Gypsum has very low thermal conductivity and maintains a low temperature when heated as it loses that heat by dehydrating; as such, gypsum is used as an insulator in materials such as plaster and drywall. The anhydrous equivalent of gypsum is anhydrite; it can form directly from seawater in highly arid conditions. The barite group has the general formula XSO4, where the X is a large 12-coordinated cation. Examples include barite (BaSO4), celestine (SrSO4), and anglesite (PbSO4); anhydrite is not part of the barite group, as the smaller Ca2+ is only in eight-fold coordination.[137]
Phosphates

The phosphate minerals are characterized by the tetrahedral [PO4]3− unit, although the structure can be generalized, and phosphorus is replaced by antimony, arsenic, or vanadium. The most common phosphate is the apatite group; common species within this group are fluorapatite (Ca5(PO4)3F), chlorapatite (Ca5(PO4)3Cl) and hydroxylapatite (Ca5(PO4)3(OH)). Minerals in this group are the main crystalline constituents of teeth and bones in vertebrates. The relatively abundant monazite group has a general structure of ATO4, where T is phosphorus or arsenic, and A is often a rare-earth element (REE). Monazite is important in two ways: first, as a REE "sink", it can sufficiently concentrate these elements to become an ore; secondly, monazite group elements can incorporate relatively large amounts of uranium and thorium, which can be used in monazite geochronology to date the rock based on the decay of the U and Th to lead.[138]
Organic minerals

The Strunz classification includes a class for organic minerals. These rare compounds contain organic carbon, but can be formed by a geologic process. For example, whewellite, CaC2O4⋅H2O is an oxalate that can be deposited in hydrothermal ore veins. While hydrated calcium oxalate can be found in coal seams and other sedimentary deposits involving organic matter, the hydrothermal occurrence is not considered to be related to biological activity.[88]
Astrobiology
It has been suggested that biominerals could be important indicators of extraterrestrial life and thus could play an important role in the search for past or present life on the planet Mars.  Furthermore, organic components (biosignatures) that are often associated with biominerals are believed to play crucial roles in both pre-biotic and biotic reactions.[139]
On January 24, 2014, NASA reported that current studies by the Curiosity and Opportunity rovers on Mars will now be searching for evidence of ancient life, including a biosphere based on autotrophic, chemotrophic and/or chemolithoautotrophic microorganisms, as well as ancient water, including fluvio-lacustrine environments (plains related to ancient rivers or lakes) that may have been habitable.[140][141][142][143] The search for evidence of habitability, taphonomy (related to fossils), and organic carbon on the planet Mars is now a primary NASA objective.[140][141]
See also

Amateur geology
Mineral (nutrient), also known as Dietary mineral
Isomorphism (crystallography)
List of minerals– A list of minerals for which there are articles on Wikipedia
List of minerals (complete)– List of minerals, intended to be as complete as possible
Mineral collecting
Polymorphism (materials science)

Notes

General references

Further reading
 On the creation of new minerals by human activity.

, largest mineral database on the Internet
 by David Barthelmy (2009)
 Mineralogical Society of America

 (Robert Hazen, NASA) (video, 60m, April 2014).
 (Robert Hazen, 15 February 2017)

What is the most abundant mineral on earth?


Rare-earth magnets are strong permanent magnets made from alloys of rare-earth elements. Developed in the 1970s and 1980s, rare-earth magnets are the strongest type of permanent magnets made, producing significantly stronger magnetic fields than other types such as ferrite or alnico magnets. The magnetic field typically produced by rare-earth magnets can exceed 1.4 teslas, whereas ferrite or ceramic magnets typically exhibit fields of 0.5 to 1 tesla.  There are two types: neodymium magnets and samarium–cobalt magnets. Magnetostrictive rare-earth magnets such as Terfenol-D also have applications, e.g. in loudspeakers. Rare-earth magnets are extremely brittle and also vulnerable to corrosion, so they are usually plated or coated to protect them from breaking, chipping, or crumbling into powder.
The development of rare-earth magnets began around 1966, when  K. J. Strnat and G. Hoffer of the US Air Force Materials Laboratory discovered that an alloy of yttrium and cobalt, YCo5, had by far the largest magnetic anisotropy constant of any material then known.[1][2]  The term "rare earth" can be misleading, as these metals are not particularly rare or precious;[3][4] they are about as abundant as tin or lead.[5]  However rare earth ores are unevenly distributed, with the major source being China,[6] which has led countries to classify rare earth metals as strategically important.[7]  Recent Chinese export restrictions on these materials have led other countries to initiate research programs to develop strong magnets that do not require them.

Explanation of strength
The rare-earth (lanthanide) elements are metals that are ferromagnetic, meaning that like iron they can be magnetized to become permanent magnets, but their Curie temperatures (the temperature above which their ferromagnetism disappears) are below room temperature, so in pure form their magnetism only appears at low temperatures.  However, they form compounds with the transition metals such as iron, nickel, and cobalt, and some of these compounds have Curie temperatures well above room temperature.  Rare-earth magnets are made from these compounds.
The greater strength of rare-earth magnets is mostly due to two factors.  First, their crystalline structures have very high magnetic anisotropy. This means that a crystal of the material preferentially magnetizes along a specific crystal axis but is very difficult to magnetize in other directions. Like other magnets, rare-earth magnets are composed of microcrystalline grains, which are aligned in a powerful magnetic field during manufacture, so their magnetic axes all point in the same direction.  The resistance of the crystal lattice to turning its direction of magnetization gives these compounds a very high magnetic coercivity (resistance to being demagnetized).
Second, atoms of rare-earth elements can have high magnetic moments because their orbital electron structure contains many unpaired electrons, in contrast to other elements, in which almost all of the electrons exist in pairs with opposite spins, so their magnetic fields cancel out.  This is a consequence of incomplete filling of the f-shell, which can contain up to 7 unpaired electrons.  In a magnet it is the unpaired electrons, aligned so they spin in the same direction, which generate the magnetic field.  This gives the materials high remanence (saturation magnetization Js).  The maximal energy density BHmax is proportional to Js2, so these materials have the potential for storing large amounts of magnetic energy.  The magnetic energy product BHmax of neodymium magnets is about 18 times greater than "ordinary" magnets by volume.  This allows rare-earth magnets to be smaller than other magnets with the same field strength.
Magnetic properties
Some important properties used to compare permanent magnets are: remanence (Br), which measures the strength of the magnetic field; coercivity (Hci), the material's resistance to becoming demagnetized; energy product (BHmax), the density of magnetic energy; and Curie temperature (TC), the temperature at which the material loses its magnetism.  Rare-earth magnets have higher remanence, much higher coercivity and energy product, but (for neodymium) lower Curie temperature than other types.  The table below compares the magnetic performance of the two types of rare-earth magnets, neodymium (Nd2Fe14B) and samarium-cobalt (SmCo5), with other types of permanent magnets.

Source:
Types
Samarium-cobalt

Samarium–cobalt magnets (chemical formula: SmCo5), the first family of rare-earth magnets invented, are less used than neodymium magnets because of their higher cost and lower magnetic field strength.  However, samarium–cobalt has a higher Curie temperature, creating a niche for these magnets in applications where high field strength is needed at high operating temperatures. They are highly resistant to oxidation, but sintered samarium-cobalt magnets are brittle and prone to chipping and cracking and may fracture when subjected to thermal shock.
Neodymium

Neodymium magnets, invented in the 1980s, are the strongest and most affordable type of rare-earth magnet.  They are made of an alloy of neodymium, iron, and boron (Nd2Fe14B), sometimes abbreviated as NIB.   Neodymium magnets are used in numerous applications requiring strong, compact permanent magnets, such as electric motors for cordless tools, hard disk drives, magnetic holddowns, and jewelry clasps. They have the highest magnetic field strength and have a higher coercivity (which makes them magnetically stable), but they have a lower Curie temperature and are more vulnerable to oxidation than samarium–cobalt magnets.  Corrosion can cause unprotected magnets to spall off a surface layer or to crumble into a powder.  Use of protective surface treatments such as gold, nickel, zinc, and tin plating and epoxy-resin coating can provide corrosion protection.
Originally, the high cost of these magnets limited their use to applications requiring compactness together with high field strength.  Both the raw materials and the patent licenses were expensive.  However, since the 1990s, NIB magnets have become steadily less expensive, and the low cost has inspired new uses such as magnetic construction toys.
Hazards
The greater force exerted by rare-earth magnets creates hazards that are not seen with other types of magnet.  Magnets larger than a few centimeters are strong enough to cause injuries to body parts pinched between two magnets or a magnet and a metal surface, even causing broken bones.[8]  Magnets allowed to get too near each other can strike each other with enough force to chip and shatter the brittle material, and the flying chips can cause injuries.  There have even been cases where young children who have swallowed several magnets have had a fold of the digestive tract pinched between the magnets, causing injury and in one case intestinal perforations, sepsis and death.[9]
The U.S. Consumer Product Safety Commission passed a rule restricting rare-earth magnet size in consumer products, but it was vacated by a US Federal court decision in November 2016.[10]
Applications
Since their prices became competitive in the 1990s, neodymium magnets have been replacing Alnico and ferrite magnets in the many applications in modern technology requiring powerful magnets.  Their greater strength allows smaller and lighter magnets to be used for a given application.
Common applications

Common applications of rare-earth magnets include:
computer hard disk drives
wind turbine generators
speakers / headphones
bicycle dynamos
MRI scanners
fishing reel brakes
permanent magnet motors in cordless tools
high-performance AC servo motors
traction motors and integrated starter-generators in hybrid and electric vehicles
mechanically powered flashlights, employing rare earth magnets for generating electricity in a shaking motion or rotating (hand-crank-powered) motion
industrial uses such as maintaining product purity, equipment protection, and quality control
capture of fine metallic particles in lubricating oils (crankcases of internal combustion engines, also gearboxes and differentials), so as to keep said particles out of circulation, thereby rendering them unable to cause abrasive wear of moving machine parts
Other applications
Other applications of rare-earth magnets include:
Linear motors (used in mag-lev trains, etc.)
Stop motion animation: as tie-downs when the use of traditional screw and nut tie-downs is impractical.
Diamagnetic levitation experimentation, the study of magnetic field dynamics and superconductor levitation.
Electrodynamic bearings
Launched roller coaster technology found on roller coaster and other thrill rides.
LED Throwies, small LEDs attached to a button cell battery and a small rare earth magnet, used as a form of non-destructive graffiti and temporary public art.
Neodymium magnet toys
Electric guitar pickups
Miniature figures, for which rare-earth magnets have gained popularity in the miniatures gaming community for their small size and relative strength assisting in basing and swapping weapons between models.
Rare-earth-free permanent magnets
The United States Department of Energy has identified a need to find substitutes for rare-earth metals in permanent-magnet technology and has begun funding such research. The Advanced Research Projects Agency-Energy (ARPA-E) has sponsored a Rare Earth Alternatives in Critical Technologies (REACT) program, to develop alternative materials. In 2011, ARPA-E awarded 31.6 million dollars to fund Rare-Earth Substitute projects.[11]

Further reading
Edward P. Furlani, "Permanent Magnet and Electromechanical Devices: Materials, Analysis and Applications", Academic Press Series in Electromagnetism (2001). ISBN0-12-269951-3.
Peter Campbell, "Permanent Magnet Materials and their Application" (Cambridge Studies in Magnetism)(1996). ISBN978-0-521-56688-9.
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 (Magnetic Materials Producers Association)

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Jay and Silent Bob Strike Back is a 2001 American comedy film written and directed by Kevin Smith, the fifth to be set in his View Askewniverse, a growing collection of characters and settings that developed out of his cult favorite Clerks. It focuses on the two eponymous characters, played respectively by Jason Mewes and Smith. The film features a large number of cameo appearances by famous actors and directors, and its title and logo for Jay and Silent Bob Strike Back are direct references to The Empire Strikes Back.
Originally intended to be the last film set in the Askewniverse, or to feature Jay and Silent Bob, Strike Back features many characters from the previous Askew films, some in dual roles and reprising roles from the previous entries. The film was a minor commercial success, grossing $33.8 million worldwide from a $22 million budget, and received mixed reviews from critics.
Five years later and following the commercial failure of Jersey Girl, Smith reconsidered and decided to continue the series with Clerks II, resurrecting Jay and Silent Bob in supporting roles.
Smith announced in February 2017 that he was writing a sequel called Jay and Silent Bob Reboot and hoped to start filming in February 2019[3][4][5][6] for a tentative release that same year.[7]
Plot

After getting a restraining order from Randal Graves (Clerks) for selling drugs outside the Quick Stop, Jay and Silent Bob find out from Brodie Bruce (Mallrats) that Bluntman and Chronic, the comic book based on their likenesses, has been adapted into a film in production by Miramax Films. In response, the two visit Holden McNeil (Chasing Amy), the co-writer of Bluntman and Chronic and demand royalties from the film. However, Holden tells Jay and Silent Bob that he sold his part of the creative and publishing rights of the comic over to his former friend Banky Edwards. Upon learning of the film, as well as the negative reaction it has received so far on the internet,[8] the two set out on a quest to Hollywood, to prevent the film from being made and tainting their image, or at the very least receive the money from the royalties owed to them.
On the way, they befriend an animal liberation group, consisting of four women: Justice, Sissy, Missy, and Chrissy; and one man, Brent, who they had picked up for the cause. It is revealed that the organization is a front; Brent is a patsy, intended as a diversion by freeing an animal from a testing laboratory while the girls rob a diamond depository nearby. Jay tricks Brent and throws him out of the van in order to get closer to Justice, with whom he is smitten. Justice, who becomes close to Jay and Silent Bob (particularly the former), reluctantly accepts the two as the new patsies.
While the girls are robbing the diamond depository, Chrissy farts loudly enough to set off the alarm, forcing them to break the glass and steal the diamonds.  While this is going on Jay and Silent Bob free the animals and take an orangutan named Suzanne with them. They escape outside to see the police arriving and the van exploding, which they believe has killed the girls.
Jay then takes the orangutan with him as a memorial to Justice.  Quickly afterwards, Federal Wildlife Marshal Willenholly (whose name is taken from the three characters in the TV show Land of the Lost: Marshal, Will and Holly) shows up at the scene. Blinded to the diamond heist, he claims to have jurisdiction because of the large number of animals that escaped. He learns that all the animals have been recovered except for the orangutan. The officers then find and watch footage of a video Sissy recorded of Jay making remarks about "the clit", claiming to be "the Clit commander". The literature accompanying the tape says that "Clit" is an acronym for Coalition for the Liberation of Itinerant Tree-Dwellers. Willenholly blindly finds this as an act of terrorism and calls for police support to hunt down what he considered "the two most dangerous men on the planet."
When the officers later have the trio cornered inside a diner and threaten to open fire, Jay and Silent Bob dress the orangutan as a child and walk out, claiming that they want to get their "son" out of the danger zone. Willenholly, thinking about the political repercussions of arresting a gay couple, decides to let them leave, but he quickly realizes his mistake and resumes the chase. When they jump into a sewer system, only Willenholly himself follows them while the other police officers, led by the Sheriff, leave him, and he is soon tricked into jumping off a dam.
Having escaped the law, Jay and Silent Bob once again return to their quest to reach Hollywood, only to have Suzanne taken by a Hollywood animal acting agency car. Now on a quest to rescue Suzanne and clear their names, the two arrive in Hollywood and find themselves in the background of an E! News newscast about their online threat against Miramax. Justice watches the news and takes the diamonds to Hollywood to set things right. Marshal Willenholly learns of their mission to reach Hollywood and leaves to find them.
After a long chase with studio security and reclaiming Suzanne from a fictional Scream 4 in production, Jay and Silent Bob end up in Jason Biggs and James Van Der Beek's dressing room, where they quickly realize that these are the actors that will play the roles of Bluntman and Chronic. Suzanne beats both of them up effortlessly and Jay and Silent Bob assume the roles of their characters. Production staff throw them on stage with racist director Chaka Luther King, and they must engage in a duel with Mark Hamill playing a comic book supervillain called Cocknocker. Eventually Willenholly arrives to capture Jay and Silent Bob, but Justice arrives to save them. Justice admits that the CLIT organization was not real and that the two were used as a diversion while she, Missy, Sissy and Chrissy, were stealing jewels. As the rest of jewel thieves arrive, a climactic final battle ensues, after which Jay and Silent Bob get their royalties to the film from Banky, and Justice turns herself and her former team in to Willenholly in exchange for a shorter sentence and letting Jay and Silent Bob go.
The film ends with Jay and Silent Bob spending their royalty to locate everyone who expressed negative opinions on the internet about the movie and characters, ranging from kids to clergy, and traveling to their towns to beat them up. The scene then cuts to everyone leaving a movie theater, having just watched the Bluntman and Chronic movie and expressing negative reception. Jay and Silent Bob, with Justice and Willenholly, then go across the street to enjoy a performance from Morris Day and The Time.
After the credits, God closes the View Askewniverse book.
Cast

Jason Mewes as Jay / Chronic
Kevin Smith as Silent Bob / Bluntman
Ben Affleck as himself / Holden McNeil / Chuckie Sullivan
Jeff Anderson as Randal Graves
Brian O'Halloran as Dante Hicks
Shannon Elizabeth as Justice
Eliza Dushku as Sissy
Ali Larter as Chrissy
Jennifer Schwalbach as Missy
Will Ferrell as Federal Wildlife Marshal Willenholly
Jason Lee as Brodie Bruce / Banky Edwards
Matt Damon as himself / Will Hunting
Judd Nelson as Sheriff
George Carlin as Hitchhiker
Carrie Fisher as Nun
Seann William Scott as Brent
Jon Stewart as Reg Hartner
Jules Asner as herself
Steve Kmetko as himself
Tracy Morgan as Pumpkin Escobar
Gus Van Sant as himself
Chris Rock as Chaka Luther King
Jamie Kennedy as Chaka's production assistant
Wes Craven as himself
Shannen Doherty as herself
Mark Hamill as Cocknocker / voice of Scooby-Doo
Marc Blucas as Fred lookalike
Matthew James as Shaggy lookalike
Jane Silvia as Velma lookalike
Carmen Llywelyn as Daphne lookalike
Diedrich Bader as Gordon, the Miramax security guard
Jason Biggs as himself
James Van Der Beek as himself
Morris Day as himself
Bryan Johnson as Steve-Dave
Walter Flanagan as Walter
Renee Humphrey as Tricia Jones
Joey Lauren Adams as Alyssa Jones
Dwight Ewell as Hooper LaMont/Hooper X
Scott William Winters as himself / Clark
William B. Davis (cameo) as The Smoking Man
Alanis Morissette (cameo) as God

Production
The film was originally titled View Askew 5 and the title was changed to Jay and Silent Bob Strike Back". Filming began on January 14, 2001 and ended on April 19, 2001. Filming took in place in New Jersey, and mostly in California.
On Kevin Smith's podcast Jay & Silent Bob Get Old, Smith explained at length about how much of a "headache" the film was to make, mostly owing to Mewes' drug and alcohol abuse turning him into a "ticking time bomb", which threatened to shut the project down at any moment. During pre-production, Mewes would have constant mood swings due to heroin withdrawal, to the point that Smith actually threw him out of his car on their way to the set one day. Mewes would compensate for his lack of drugs by drinking heavily after every day of shooting and nearly got into a fist fight with Scott Mosier when he had to come back one night for a re-shoot while drunk (Mewes later said that he was too intoxicated to remember anything that happened during production). When the shoot wrapped, Smith told Mewes point-blank to get sober or he would never speak to him again.
Release
Box office
Jay and Silent Bob Strike Back grossed $30.1 million in the United States and Canada and $3.7 million in other territories for a worldwide total of $33.8 million, against a production budget of $22 million.[2]
The film grossed $11 million in its opening weekend, finishing third at the box office behind two other comedy sequels, American Pie 2 ($12.5 million) and Rush Hour 2 ($11.6 million).[9]
Critical reception
Jay and Silent Bob Strike Back received mixed reviews from critics. On review aggregator Rotten Tomatoes the film has an approval rating of 53% based on 152 reviews, with an average rating of 5.6/10. The site's critical consensus reads, "Fans can expect a good laugh as the cast from Smith's previous films reunite for Jay and Silent Bob's last bow. The loose plotting and crude language may be too much for others though."[10] On Metacritic the film has a score of 51 out of 100, based on 31 critics, indicating "mixed or average reviews".[11] Audiences surveyed by CinemaScore gave the film an average grade of "B+" on an A+ to F scale.[12]
Roger Ebert gave the film 3 out of 4 stars, writing that "[w]hether you will like 'Jay and Silent Bob' depends on who you are ... Kevin Smith's movies are either made specifically for you, or specifically not made for you".[13] Adam Smith of Empire gave the film 3/5 stars, writing that "[w]hen it's good it's very, very good, but when it's bad it's offensive", and noting that "the gag hit/miss ratio is really only about 50/50".[14] Scott Tobias of The A.V. Club wrote that "[e]ven at a slim 95 minutes, Jay And Silent Bob lets initially funny scenes trail off into long-winded monologues and silly digressions", and Elvis Mitchell of The New York Times called the film "[may]be the greatest picture ever made for 14-year-old boys. Mr. Smith may have hit his target, but he aimed very low."[15][16]
Home media
Jay and Silent Bob Strike Back was released on VHS and Dimension Collector's Series two-disc DVD on February 26, 2002. A Blu-ray version of the film was released on September 19, 2006.
Soundtrack

Music from the Dimension Motion Picture: Jay and Silent Bob Strike Back, the soundtrack to the film, was released on August 14, 2001 by Universal Records. Varèse Sarabande released the original score by James L. Venable. It alternates film dialogue with songs of various genres that appear in the film. It features the 2001 Afroman hit, "Because I Got High", whose music video featured the characters Jay and Silent Bob.
Interlude: Cue Music by Jason Lee (as Brodie Bruce) – 0:03
"Jay's Rap 2001" by Jason Mewes (as Jay) – 0:32
"Kick Some Ass" by Stroke 9 – 4:05
Holden on Affleck by Ben Affleck as Holden McNeil – 0:28
"Tube of Wonderful" by Dave Pirner – 1:45
Cyber Savvy by Ben Affleck and Jason Mewes (as Holden and Jay) – 0:07
"Choked Up" by Minibar – 2:58
Doobie Snacks by Jason Mewes (as Jay) – 0:08
"Magic Carpet Ride" by Steppenwolf – 2:43
Jay & Justice by Shannon Elizabeth and Jason Mewes (as Justice and Jay) – 0:11
"Bad Medicine" by Bon Jovi – 3:55
Stealing Monkeys – 0:08
"This Is Love" by PJ Harvey – 3:45
Advice from Above – 0:23
"The Devil's Song" by Marcy Playground – 2:52
Idiots vs. The Internet – 0:06
"Tougher Than Leather" by Run-D.M.C. – 4:23
Willenholly's Woe by Will Ferrell (as Willenholly) – 0:09
"Bullets" by Bob Schneider – 4:22
Touching a Brother's Heart by Jason Mewes and Tracy Morgan (as Jay and drug dealer) – 0:23
"Hiphopper" by Thomas Rusiak featuring Teddybears STHLM – 4:46
Two Thumbs Up by Chris Rock (as Chaka Luther King) – 0:07
"Jackass" by Bloodhound Gang – 2:26
A Smooth Pimp and a Man Servant by Jason Mewes (as Jay) – 0:16
"Jungle Love" by Morris Day and The Time – 3:03
NWP by Chris Rock (as Chaka Luther King) – 0:14
"Because I Got High" by Afroman – 3:18
MPAA rating and GLAAD controversy
In August 2001, three weeks prior to release, the film came under fire from the Gay & Lesbian Alliance Against Defamation (GLAAD), for its "overwhelmingly homophobic tone",[17] which included an abundance of gay jokes and characters excessively using the term "gay" to mean something derogatory. The scenes deemed particularly offensive included Jay's vehement refusal of giving oral sex to a male driver when hitchhiking, and Jay chastising Silent Bob for being willing to perform fellatio on him to get the security guard to let them go. Following an advance screening of the film, former GLAAD media director Scott Seomin asked Smith to make a $10,000 donation to the Matthew Shepard Foundation, as well as to include a reference to GLAAD's cause in the ending credits.[18][19]
On the bonus DVD (176 minutes), Smith explains in the on-camera intros of the deleted scenes that several scenes had to be cut from the theatrical release, due to the film initially receiving an NC-17 rating from the MPAA. He also mentions in the audio commentary of the feature film that it took three submissions to the MPAA for the film to earn an R rating.
See also
Oh, What a Lovely Tea Party, a documentary about the making of the film
List of films featuring fictional films
Notes
According to Ethan Alter of Film Journal International, Smith did not intend to make another View Askewniverse film upon completion of Jay and Silent Bob Strike Back, but only decided to do so several years later, following the unsuccessful release of Jersey Girl.[20]
Will Ferrell would later star in the 2009 film adaptation of Land of the Lost as Dr. Rick Marshall alongside Danny McBride as Will Stanton and Anna Friel as Holly Cantrell.

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Cargo is a 2017 Australian post-apocalyptic drama thriller film directed by Ben Howling and Yolanda Ramke with a screenplay by Ramke based on their 2013 short film of the same name.[1][2] The film stars Martin Freeman, Anthony Hayes, Susie Porter, and Caren Pistorius.[3]. It premiered at the Adelaide Film Festival on 6 October 2017 and was released in cinemas in Australia on 17 May 2018, worldwide except for Australia on 18 May 2018 by Netflix and on Netflix in Australia on 16 November 2018.[4]
Plot

In a world overtaken by a virus that turns people into zombies within 48 hours, the Rose family—Andy, Kay, and their baby Rosie—are living safely on a houseboat in rural Australia. Short on food, Andy investigates an abandoned sailboat and retrieves various supplies. Later, Kay goes to collect more, but is attacked by a zombie inside.
Meanwhile, an Aboriginal girl, Thoomi, attempts to protect her infected father by feeding him wildlife and keeping him locked up while her tribe eliminate the undead. In doing so, she distances herself from her mother, who is frantically searching for her.
Andy discovers Kay in the bathroom of the houseboat, trying to stop the bleeding from a bite on her knee. They set out to find a hospital, but crash after evading a man in the middle of the road. Kay is impaled and Andy faints from shock; he wakes hours later and is bitten by a turned Kay as he gets Rosie out of the car. Andy prepares to defend himself against the man, noticing he is a zombie. Thoomi appears and dissuades Andy from hurting her father.
Andy arrives at a school and meets Etta, a teacher. He considers giving her Rosie, but she advises him to continue his journey. Andy later finds a truck and attempts to hijack it, but is stopped by its trapped owner, Vic. Andy frees him and they escape to Vic's shelter where Andy meets Lorraine, who he assumes is Vic's wife. He leaves Rosie with Lorraine and leaves with Vic, where they shoot groups of zombies and collect their valuables. Vic attracts the zombies by imprisoning healthy humans inside cages as bait; Andy is perturbed to see Thoomi trapped.
That night, Andy attempts suicide, but Lorraine stops him and confesses that she is not Vic's wife and knows he is infected. Vic knocks Andy out, and he awakens in the same cage as Thoomi. They agree to help each other escape by using the combined force of many zombies to open their cage; they return to the shelter, rendezvousing with Lorraine and Rosie. Vic shoots at them as they escape, and Lorraine uses herself as a shield and is killed.
Thoomi and Andy evade Vic, spending the night in a small gulch. The following morning, Thoomi runs off after Andy asserts her father will not get better. Thoomi looks for her father, finding him straddled atop a tree, dead. Andy arrives to comfort her, but leaves promptly when he cannot console Thoomi, as she blames him for delaying her. Thoomi remains at the tree grieving, but is able to hear Rosie's cry and catches up with Andy.
They travel by motorboat to the campsite where Andy previously saw a family, inspecting the RV in which they were staying. Andy leaves with Rosie to go find the family, while Thoomi stays in the RV. He meets the father, who has been bitten. The father offers Andy a revolver once he uses four of the bullets to kill himself and his family. The father executes his plan, and Andy collects the gun as intended and debates whether to shoot himself as well. Thoomi rushes to them, and they travel towards nearby smoke.
As they pass through a train tunnel, they encounter Vic. Thoomi hides with Rosie inside a parked vehicle on the tracks, while Andy tries to distract Vic. The two men fight. During the struggle, Vic manages to obtain the revolver and shoot Andy. He rises to check on Thoomi and Rosie, who Vic is cradling, lamenting the death of Lorraine. He tearfully hands over Rosie so that Andy can renew his walk.
Andy has another lapse, almost indulging in decayed meat. With little time left, Andy asks of Thoomi to promise to look after Rosie, with whom Andy shares a farewell before preparing himself for the transformation by placing a guard in his mouth, binding his wrists, and wrapping meat on a stick.
They catch up to the Aboriginal warriors as they finish killing several zombies, but Thoomi calls out to them with a whistle, drawing the attention of her mother. Thoomi and Rosie are riding Andy, who is detained by the warriors while Thoomi and Rosie are welcomed back. She takes out Kay's perfume bottle and sprays it, the smell pacifying Andy who seems to acknowledge Rosie is finally safe. Thoomi allows a warrior to put Andy out of his misery.
The Aboriginal people are seen traveling to a refuge of their people where they are welcomed heartily. As Thoomi and her mother inspect Rosie, the words Thank You are read on her stomach, written in white paint which Thoomi and the warriors have used to disguise their scent from the zombies.
Cast
Martin Freeman as Andy Rose
Anthony Hayes as Vic Carter
Susie Porter as Kay Caine
Caren Pistorius as Lorraine Cassidy
David Gulpilil as Daku, the Clever Man
Kris McQuade as Etta
Bruce R. Carter as Willie
Natasha Wanganeen as Josie
Simone Landers as Thoomi
Release
The film was originally scheduled to be released on 8 June 2018.[5] However, it was later brought forward to 18 May 2018.[6][7][8][9] The film is dedicated in memory of Dr. G. Yunupingu, an Aboriginal Australian singer who died aged 46 on 26 July 2017.[10]
Reception
Cargo received mixed to positive reviews from critics, praising its emotional depth and Freeman's performance. On review aggregator website Rotten Tomatoes, the film holds an approval rating of 86%, based on 65 reviews, and an average rating of 7.1/10. The website's critical consensus reads, "Cargo takes a refreshingly character-driven approach to the zombie genre that's further distinguished by its Australian setting and Martin Freeman's terrific lead performance."[11] On Metacritic, the film has a weighted average score of 65 out of 100, based on 12 critics, indicating "generally favorable reviews".[12]
The film has been described as a tribute to the 2009 film The Road.
[7][8] In a positive review, Brian Tallerico of RogerEbert.com stated he believed George A. Romero would have enjoyed the film.[13] Clark Collins of Entertainment Weekly gave the film a 'B', saying: "The Australian setting brings a fresh, and epic, quality to this now done-to-death genre".[14] However, Frank Scheck of The Hollywood Reporter criticized the film for being "unlikely to satisfy either viewers looking for serious-minded fare or horror fans looking for genuine frights", but praised Freeman's "quietly intense" performance.[15]
Accolades

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