Economic geology is a branch of geology that deals with economically valuable geological materials.
In broader terms, economic geology is concerned with the distribution of mineral deposits, the economic considerations involved in their recovery, and assessment of the reserves available.
Economic Geology deals with materials such as precious and base metals, non-metallic minerals, fossil fuels, and other materials of commercial value, such as salt, gypsum, and building stone. It makes use of the principles and methods of various other fields, especially geophysics, structural geology, and stratigraphy.
Economic geology is not only practised by geologists but it is also of some interest to engineers, investment bankers, environmental scientists and conservationists because of the huge impact extractive industries have on the socioeconomic and environmental scene.
Origin and Development of Economic Geology:
The concept of economic geology is a relatively new one, even though humans have been extracting metals and minerals of value from the ground since prehistoric times. For all their ability to appreciate the worth of such resources, however, pre-modern people possessed little in the way of scientific theories regarding either their formation or the means of extracting them.
The Greeks, for instance, believed that veins of metallic materials in the earth indicated that those materials were living things putting down roots after the manner of trees. Astrologers of medieval times maintained that each of the “seven planets” (Sun, Moon, and the five planets, besides
Earth, known at the time) ruled one of the seven known metals—gold, copper, silver, lead, tin, iron, and mercury—which supposedly had been created under the influence of their respective “planets.”
The first thinker who attempted to go beyond such unscientific (if imaginative) ideas was a German physician writing under the Latinised name Georgius Agricola (1494-1555). As a result of treating miners for various conditions, Agricola, whose real name was Georg Bauer, became fascinated with minerals.
Regarded as the father of both mineralogy and economic geology, Agricola introduced several ideas that provided a scientific foundation for the study of Earth and its products. In De Ortu et causis Subterraneorum (1546), he critiqued all preceding ideas regarding the formation of ores, including the Greek and astrological notions mentioned earlier as well as the alchemical belief that all metals are composed of mercury and sulphur.
Instead, he maintained that subterranean fluids carry dissolved minerals, which, when cooled, leave deposits in the cracks of rocks and thus give rise to mineral veins. Agricola’s ideas later helped form the basis for modern theories regarding the formation of ore deposits.
In De Natura Fossilium (On the Nature of Fossils, 1546), Agricola also introduced a method for the classification of “fossils”, as minerals were then known. Agricola’s system, which categorises minerals according to such properties as colour, texture, weight, and transparency, is the basis for the system of mineral classification in use today.
Of all his works, however, the most important was De re Metallica, which would remain the leading textbook for miners and mineralogists during the two centuries that followed. In this monumental work, he introduced many new ideas, including the concept that rocks contain ores that are older than the rocks themselves. He also explored in detail the mining practices in use in his time, itself an extraordinary feat in that miners of the sixteenth century tended to guard their trade secrets closely.
Rocks and Minerals:
Our earth’s crust is made up of rocks which, in turn, are aggregates of minerals. To be designated as a mineral species, a substance must be found in nature and be of inorganic origin. It must possess a definite chemical characteristic and a distinctive atomic formation.
A rock is an aggregate of minerals or organic material, which can appear in consolidated or unconsolidated form. Rocks are of three different types: igneous, formed by crystallisation of molten minerals, as in a volcano; sedimentary, usually formed by deposition, compaction, or cementation of weathered rock; and metamorphic, formed by alteration of pre-existing rock. Rocks made from organic material are typically sedimentary, an example being coal.
Rocks have possessed economic importance from a time long before ‘economics’ as we know it existed—a time when there was nothing to buy and nothing to sell. That time, of course, would be the Stone Age, which dates back practically to the beginnings of the human species and overlapped with the beginnings of civilization some 5,500 years ago. In the hundreds of thousands of years when stone constituted the most advanced tool making material, humans developed an array of stone devices for making fire, sharpening knives, killing animals (and other humans), cutting food or animal skins, and so on.
The Stone Age, both in the popular imagination and (with some qualifications) in actual archaeological fact, was a time when people lived in caves. Since that time, of course, humans have generally departed from the caves, though exceptions exist, as the United States military found in 2001 when attempting to hunt for terrorists in the caves of Afghanistan.
In any case, the human attachment to stone dwellings has taken other forms, beginning with the pyramids and continuing through today’s masonry homes. Nor is rock simply a structural material for building, as the use of gypsum wallboard, slate countertops, marble finishes, and graveled walkways attests. And, of course, construction is only one of many applications to which rocks and minerals are directed, as we shall see.
Of all known chemical elements, 87, or about 80 per cent, are metals. The latter group is identified as being lustrous or shiny in appearance and malleable or ductile, meaning that they can be moulded into different shapes without breaking them. Despite their ductility, metals are extremely durable, have high melting and boiling points, and are excellent conductors of heat and electricity. Some register high on the Mohs hardness scale.
Whereas there are only 87 varieties of metal, there are some 3,700 types of mineral. There is considerable overlap between metals and minerals, but that overlap is far from complete: many minerals include nonmetallic elements, such as oxygen and silicon. A mineral is a substance that appears in nature and therefore cannot be created artificially, is inorganic in origin, has a definite chemical composition, and possesses a crystalline internal structure.
The term organic does not refer simply to substances with a biological origin; rather, it describes any compound that contains carbon, with the exception of carbonates (which are a type of mineral) and oxides, such as carbon dioxide or carbon monoxide.
The fact that a mineral must be of non-varying composition limits minerals almost exclusively to elements and compounds—that is, either to substances that cannot be broken down chemically to yield simpler substances or to substances formed by the chemical bonding of elements. Only in a few highly specific circumstances are naturally occurring alloys, or mixtures of metals, considered minerals.
Minerals are classified into eight basic groups as per their chemical composition:
i. Native elements
iii. Oxides and hydroxides
v. Carbonates, nitrates, borates, iodates
vi. Sulphates, chromates, molybdates, tungstates
vi. Phosphates, arsenates, vanadates
The first group, native elements, includes metallic elements that appear in pure form somewhere on Earth; certain metallic alloys, alluded to earlier; as well as native nonmetals, semi-metals, and minerals occur with metallic and nonmetallic elements. The native elements, along with the six classes that follow them in this list, are collectively known as nonsilicates, a term that emphasises the importance of the eighth group.
The vast majority of minerals, including the most abundant ones, belong to the silicates class, which is built around the element silicon. Just as carbon can form long strings of atoms, particularly in combination with hydrogen (as we discuss in the context of fossil fuels later in this essay), silicon also forms long strings, though its “partner of choice” is typically oxygen rather than hydrogen. Together with oxygen, silicon—known as a metalloid because it exhibits characteristics of both metals and nonmetals—forms the basis for an astonishing array of products, both natural and man-made.
Minerals may be classified according to their use in industry as follows:
(a) Metallic minerals: Ferrous group. They include minerals like iron, chromite, manganese and nickel.
(b) Metallic minerals: Non-ferrous group. These feature copper, lead, zinc, tungsten, aluminium, vanadium and others.
(c) Non-metallic minerals. They are mica, steatite, asbestos and others.
(d) Refractory minerals. They are used as heat resistant’s in furnaces and moulds. They include chromite, magnesite, kyanite, fireclays, sillimanite and graphite.
(e) Fertilizer minerals such as gypsum, rock phosphate and pyrite.
(f) Mineral fuels such as coal, petroleum, natural gas and nuclear minerals.
The economic development of a country is influenced by the availability of minerals. Minerals form the base for several large-scale industries. Agriculture, too, is influenced by the availability of minerals in the form of fertilizers.
As noted earlier, the focus of economic geology is on both rocks and minerals, on the one hand, and fossil fuels, on the other. Fossil fuels may be defined as fuels (specifically, coal, oil, and gas) derived from deposits of organic material that have experienced decomposition and chemical alteration under conditions of high pressure.
Given this derivation from organic material, by definition, all fossil fuels are carbon- based, and, specifically, they are built around hydrocarbons—chemical compounds whose molecules are made up of nothing but carbon and hydrogen atoms.
Theoretically, there is no limit to the number of possible hydrocarbons. Carbon forms itself into apparently limitless molecular shapes, and hydrogen is a particularly versatile chemical partner. Hydrocarbons may form straight chains, branched chains, or rings, and the result is a variety of compounds distinguished not by the elements in their makeup or even (in some cases) by the numbers of different atoms in each molecule, but rather by the structure of a given molecule.
Real-Life Applications of Economic Geology:
The organic material that has decomposed to create the hydrocarbons in fossil fuels comes primarily from dinosaurs and prehistoric plants, though it just as easily could have come from any other organisms that died in large numbers a long, long time ago. To form petroleum, there must be very large quantities of Organic material deposited along with sediments and buried under more sediment. The accumulated sediments and organic material are called source rock.
What happens after accumulation of this material is critical and depends a great deal on the nature of the source rock. It is important that the organic material—for example, the vast numbers of dinosaurs that died in a mass extinction about 65 million years ago—not be allowed simply to rot, as would happen in an aerobic, or oxygen-containing, environment. Instead, the organic material undergoes transformation into hydrocarbons as a result of anaerobic chemical activity, or activity that takes place in the absence of oxygen.
Good source rocks for this transformation are shale or limestone, provided the particular rocks are composed of between 1 per cent and 5 per cent organic carbon. The source rocks should be deep enough that the pressure heats the organic material, yet not so deep that the pressure and temperature cause the rocks to undergo metamorphism or transform them into graphite or other non-hydrocarbon versions of carbon. Temperatures of up to 302 °F (150 °C) are considered optimal for petroleum generation.
Once generated, petroleum gradually moves from the source rock to a reservoir rock or a rock that stores petroleum in its pores. A good reservoir rock is one in which the pore space constitutes more than 30 per cent of the rock volume. Yet the rock must be sealed by another rock that is much less porous; indeed, for a seal or cap rock, as it is called, a virtually impermeable rock is preferred. Thus, the best kind of seal-forming rock is one made of very small, closely fitting pieces of sediment, for instance shale. Such a rock is capable of holding petroleum in place for millions of years until it is ready to be discovered and used.
People have known about petroleum from prehistory, simply because there were places on Earth where it literally seeped from the ground. The modern era of petroleum drilling, however, began in 1853, when an American lawyer named George Bissell (1821-1884) recognised its potential for use as a lamp fuel. He hired ‘Colonel’ Edwin Drake (1819-1880) to oversee the drilling of an oil well at Titusville, Pennsylvania, and in 1859 Drake struck oil. The legend of Wack gold’, of fortunes to be made by drilling holes in the ground, was born.
In the wake of the development and widespread application of the internal-combustion engine during the latter part of the nineteenth and the early part of the twentieth century’s, interest in oil became much more intense, and wells sprouted up around the world. Sumatra, Indonesia yielded- oil from its first wells in 1885, and in 1901, successful drilling began in Texas—the source of many a Texas-sized fortune. An early form of the company known today as British Petroleum (BP) discovered the first Middle Eastern oil in Persia (now Iran) in 1908. Over the next 50 years, the economic importance and prospects of that region changed considerably.
With the vast expansion in automobile ownership that began following World War I (1914- 1918) and reached even greater heights after World War II (1939-1945), the value and importance of petroleum soared. The oil industry boomed, and, as a result, many geologists found employment in a sector that offered far more in the way of financial benefits than university or government positions ever could. Today geologists assist their employers in locating oil reserves, not an easy task because so many variables must line up to produce a viable oil source. Given the cost of drilling a new oil well, which may run to $30 million or more, it is clearly important to exercise good judgments in assessing the possibilities of finding oil.
The oil industry has been fraught with environmental concerns over the impact of drilling (much of which takes place offshore, on rigs placed in the ocean); possible bio-hazards associated with spills, such as the one involving the Exxon Valdez in 1989; and the effect on the atmosphere of carbon monoxide and other greenhouse gases produced by petroleum-burning internal- combustion engines. There is even more wide- ranging concern over United States’ dependence on oil sources in foreign countries (some of which are openly hostile to the United States) as well as the possible dwindling of resources.
At the present rate of consumption, oil reserves are estimated to be exhausted by about the year 2040, but this takes into account only reserves that are considered viable today. As exploration continues, more resources may be tapped. In the long run, however, it will be necessary to develop new means of fuelling the industrialised world, because petroleum is a non-renewable resource: there is only so much of it underground, and when it is gone, it will not be replaced for millions of years (if at all).
Petroleum itself is a raw material from which numerous products, collectively known as petrochemicals or petroleum derivatives, are obtained. Through a process termed fractional distillation, the petrochemicals of the lowest molecular mass boil off first, and those having higher mass separate at higher temperatures?
Silicon, Silicates, and Other Compounds:
Just as carbon is at the centre of a vast world of hydrocarbons, so silicon is equally important to inorganic substances ranging from sand or silica (Si02) to silicone (a highly versatile set of silicon- based products), to the rocks known as silicates.
Silicates are the basis for several well-known mineral types, including garnet, topaz, zircon, kaolinite, talc, mica, and the two most abundant minerals on Earth, feldspar and quartz. (Note that most of the terms used here refer to a group of minerals, not to a single mineral.) Made of compounds formed around silicon and oxygen and comprising various metals, such as aluminum, iron, sodium, and potassium, the silicates account for 30 per cent of all minerals. As such, they appear in everything from gemstones to building materials; yet they are far from the only notable products centered on silicon.
Silicone and Other Compounds:
Silicone is not a mineral; rather, it is a synthetic product often used as a substitute for organic oils, greases, and rubber. Instead of attaching to oxygen atoms, as in a silicate, silicon atoms in silicone attach to organic groups, that is, molecules containing carbon. Silicone oils frequently are used in place of organic petroleum as a lubricant because they can withstand greater variations in temperature.
And because the body tolerates the introduction of silicone implants better than it does organic ones, silicones are used in surgical implants as well. Silicone rubbers appear in everything from bouncing balls to space vehicles, and silicones are also present in electrical insulators, rust preventives, fabric softeners, hair sprays, hand creams, furniture and automobile polishes, paints, adhesives, and even chewing gum.
Even this list does not exhaust the many applications of silicon, which (together with oxygen) accounts for the vast majority of the mass in Earth’s crust. Owing to its semi-metallic qualities, silicon is used as a semiconductor of electricity.
Computer chips are tiny slices of ultra-pure silicon, etched with as many as half a million microscopic and intricately connected electronic circuits. These chips manipulate voltages using binary codes, for which 1 means “voltage on” and 0 means “voltage off.” By means of these pulses, silicon chips perform multitudes of calculations in seconds—calculations that would take humans hours or months or even years.
A porous form of silica known as silica gel absorbs water vapour from the air and is often packed alongside moisture-sensitive products, such as electronics components, to keep them dry. Silicon carbine, an extremely hard crystalline material manufactured by fusing sand with coke (almost pure carbon) at high temperatures, has applications as an abrasive.
An ore is a rock or mineral that possesses economic value. But a more targeted definition would include the adjective metalliferous, since economically valuable minerals that contain no metals usually are treated as a separate category—industrial minerals. Indeed, it can be said that the interests of economic geology are divided into three areas: ores, industrial minerals, and fuels, which we have discussed already.
The very word ‘ore’ seems to call to mind one of the oldest-known metals in the world and probably the first material worked by prehistoric metallurgists: gold. Even the Spanish word for gold, oro, suggests a connection. When conquistadors from Spain arrived in the New World after about 1500, oro was their obsession, and it was said that the Spanish invaders of Mexico found every bit of gold or silver ore located on the surface of the earth. However, miners of the sixteenth century lacked much of the knowledge that helps geologists today find ore deposits that are not on the surface.
Locating and Extracting Ores:
The modern approach uses knowledge gained from experience. As in Agricola’s day, much of the wealth possessed by a mining company is in the form of information regarding the means of best seeking out and retrieving materials from the solid earth. Certain surface geochemical and geophysical indicators help direct the steps of geologists and miners searching for ore. Thus, by the time a company in search of ore begins drilling, a great deal of exploratory work has been done. Only at that point is it possible to determine the value of the deposits, which may simply be minerals of little economic interest.
It is estimated that a cubic mile (1.6 km3) of average rock contains about $1 trillion worth of metals, which at first sounds promising—until one does the math. A trillion dollars is a lot of money, but 1 cu. mi. (equal to 5,280 x 5,280 x 5,280 ft., or 1,609 km3) is a lot of space too. The result is that 1 cu. ft. (0.028 m3) is worth only about $6.79. But that is an average cubic foot in an average cubic mile of rock, and no mining company would even consider attempting to extract metals from an average piece of ground. Rather, viable ore appears only in regions that have been subjected to geologic processes that concentrate metals in such a way that their abundance is usually many hundreds of times greater than it would be on Earth as a whole.
Ore contains other minerals, known as gangue, which are of no economic value but which serve as a telltale sign that ore is to be found in that region. The presence of quartz, for example, may suggest deposits of gold. Ore may appear in igneous, metamorphic, or sedimentary deposits as, well as in hydrothermal fluids. The latter are emanations from igneous rock, in the form of gas or water, which dissolve metals from rocks through which they pass and later deposit the ore in other locations.
Confronting the Hazards of Mining:
Mining, a means of extracting not only ores but many industrial minerals and fuels, such as coal, is difficult work fraught with numerous hazards. There are short-term dangers to the miners, such as cave-ins, flooding, or the release of gases in the mines, as well as long-term dangers that include such mining-related diseases as black lung (typically a hazard of coal miners). Then there is the sheer mental and emotional stress that comes from spending eight or more hours a day away from the sunlight, in claustrophobic surroundings.
And, of course, there is the environmental stress created by mining—not just by, the immediate impact of cutting a gash in Earth’s surface, which may disrupt ecosystems on the surface, but myriad additional problems, such as the seepage of pollutants into the water table. Abandoned mines present further dangers, including the threat of subsidence, which make these locations unsafe in the long term.
Higher environmental and occupational safety standards, established in the United States during the last third of the twentieth century, have led to changes in the way mining is performed as well as in the way mines are left when the work is completed. For example, mining companies have experimented with the use of chemicals or even bacteria, which can dissolve a metal underground and allow it to be pumped to the surface without the need to create actual underground ‘shafts and tunnels or to send human miners to work them.
Industrial Minerals and Other Products:
Industrial minerals, as noted earlier, are non- metal—containing mineral resources of interest to economic geology. Examples include asbestos, a generic term for a large group of minerals that are highly resistant to heat and flame; boron compounds, which are used for making heat- resistant glass, enamels, and ceramics; phosphates and potassium salts, used in making fertilizers; and sulphur, applied in a range of products, from refrigerants to explosives to purifiers used in the production of sugar.
Just one industrial mineral, corundum (from the oxides class of mineral), can have numerous uses. Extremely hard, corundum in the form of an unconsolidated rock commonly called emery has been used as an abrasive since ancient times. Owing to its very high melting point—even higher than that of iron—corundum also is employed in making alumina; a fire-proof product used in furnaces and fireplaces. Though pure corundum is colourless, trace amounts of certain elements can yield brilliant colours: hence, corundum with traces of chromium becomes a red ruby, while traces of iron, titanium, and other elements yield varieties of sapphire in yellow, green, and violet as well as the familiar blue.
Environmental Impact of Economic Geology:
A few decades ago most geologists were engaged in the exploration and development of mineral resources. However, economic geology and the application of geology to problems of the urban environment are slowly demanding the services of an increasing number of geologists. Today a sufficient number of economic geologists are interested in environmental problems (many are not tied to mining, and have interests in geochemistry and petrology). They subscribe to the thought that “mineral resources will always be needed”, but “environmental issues are a major factor in mining feasibility”.
There is now a greater interest in the environment than ever before and we face concerns about the environmental impacts of almost every aspect of our daily lives. Water, soil, air and the biological environment can all be changed dramatically by the activities of industrial societies like our own, not least through mechanisms which are controlled by essentially geological processes.
Waste disposal, contamination of land by industry, the impacts of mining, water pollution and even air quality (through the dispersion of airborne mineral particles) are affected by geological processes and phenomena controlled by the composition, distribution, structure and behaviour of the underlying rocks. Everyday environmental problems are thus influenced to a greater or lesser extent by geology. The course aims to provide a broad overview of these many and various aspects of environmental geology, providing the scientific framework for understanding key environmental issues.
Environmental concerns are a major factor in determining whether mineral deposits will be developed and mined. Most economic geologists and mining companies support efforts to decrease environmental degradation due to mining.
Mining, no less than agriculture, has always been essential to humanity’s progress. Indeed, we now make use of most elements in the periodic table. However, as. overpopulation and the quest for a higher standard of living pave increased demand for minerals and metals, concern over the effects of mining and drilling in the natural environment has grown and it has become increasingly apparent that the Earth’s resources are not inexhaustible.
In its report in 1987, ‘Our Common Future’, the United Nations World Commission on Environment and Development pointed out that the world manufactures seven times more goods than it did in 1950. The commission proposed ‘sustainable development’, a marriage of economy and ecology as the only practical solution, i.e., growth without damage to the environment.
Most mines have an on-site mineral processing plant and many metal mines have a nearby smelter. For a general assessment of the environmental impact of developing new mining operations we must consider the effects of the three. The term mining is here taken to include all extractive operations, e.g., quarrying. The major areas of concerns are dealt with below.
Damage to land:
It has been estimated that the cumulative world use of land for mining between 1976 and 2000 would be about 37,000 square km, that is, about 0.2 per cent of the land surface. More developed countries have a greater proportion of disturbed ground than the less developed. The degree of reclamation of this ground is now accelerating rapidly and good use being made of old holes for the disposal of old mine, domestic and other wastes.
Other mined over areas have been turned into nature reserves and recreational parks. Future mines may be less likely to produce sites for waste disposal as most are now backfilled. This is a very necessary operation as each year an estimated 27,000 Mt of non-fuel minerals and overburden are taken from the earth’s crust.
Release of toxic substances:
Metals are not only important for the usage we make of them, but they are also an integral part of our make-up and that of other living organisms. However, while some metallic elements are essential components of living organisms, either deficiencies or excess of these can be very damaging to life. Excesses in the natural environment can arise when it is penetrated by mine waters which may issue from the mine itself, or from waste heaps.
Some metals, e.g., cadmium, mercury and metalloids, like antimony, arsenic, which are very common in small amounts in many polymetallic sulphides ores and are indeed often recovered as byproducts, are highly toxic, even in small quantities, particularly in a soluble form which can be absorbed by living organisms.
The same applies to lead, but mercifully it is fairly unreactive unless ingested and fortunately most lead minerals that form in nature are very insoluble in ground water. Cyanide has long been used for gold extraction in mineral processing plants and in the world’s largest gold field, the Witwaterstrand Basin, USA, there is major contamination of surface water with cobalt, manganese, lead, and zinc as a result of the cyanidation process and oxidation by acid mine waters. Cyanide itself is not a problem as it breaks down under the influence of ultraviolet light in near surface layers. Nevertheless, in developed countries, legislation now requires the establishment of cyanide neutralisation plants at all industrial undertakings using this chemical.
Acid mine drainage:
Acid waters generated by present or past mining result froth the oxidation, in the presence of air, water and bacteria, of sulphide minerals, particularly pyrite. They may therefore develop in coal fields as well as orefields. Suphuric acids and iron oxides are generated. The acid attacks other minerals, producing solutions which may carry toxic elements, e.g., cadmium, arsenic into local environment. Acid water generation may occur during the exploration, operation and closure stages of a mine. These waters may issue from three main sources: the mine’s dewatering system; tailings disposal facilities; and water heaps.
The discharge may only produce minor effects such as local discolouration of soils and streams with precipitated iron oxides, or lead to extensive aerial pollution of whole river system and farmland. In some mining fields, this problem is at its worst after mine closures have taken place. This is due to the water table rebound that occurs after pumping equipment is removed and this has become an urgent problem in British coalfields, which were and are dominantly underground mines working high sulphur coals, as mine closures accelerated over the last decade.
Industrial minerals Industrial mineral operations have the same general environmental impact on land and ground water disturbances as metalliferous or coal-mining, although the impact is generally less marked since the mines are usually smaller and shallower, and normally less waste is produced because in most cases ore grades are higher than in metal mining.
Pollution hazards owing to heavy metals or acid waters are low or non-existent and atmospheric pollution, caused by the burning of coal or the smelting of metallic ores, is much less serious or absent. The excavations created by industrial mineral operations are often close to conurbations, in which case these holes in the ground may be of great value as landfill sites for city waste.
Legal means of enforcing anti-pollution measures are very necessary, although it must be pointed out that many international mining companies are now adhering to the strictest self-regulation even in countries where such legislation is minor or non-existent.
Environmental impact statements:
In many countries it is now mandatory that a company proposing to apply for planning permission to commence a mineral operation prepares such a statement. This covers every aspect from effects on vegetation, climate, air quality, noise, ground and surface water to the proposed methods of ground reclamation at the termination of the operation. In some countries a bond must be deposited to assure that reclamation does take place.
These statements must include records of the condition of the environment in the potential mining area when planning permission is applied for. Companies now collect such data during exploration stage, including surface descriptions and photographs, geochemical analyses showing background levels of metals and acidity and details of the flora and fauna.
From the planning and regulatory authorities’ point of view these reports present the most effective means of minimising detrimental effects from the outset, but they may also be of great benefit to the developer because (i) they will help to obtain planning permission in the shortest possible time, and (ii) they often reveal aspects of the operation requiring attention at the outset and thus avoid expensive modifications in the future.
Bugs and in situ Mining:
Many sulphide deposits, i.e., porphyry coppers, are overlain by oxidised ores. Such ores can be mined, if necessary, by fracturing them by blasting and then pumping acid solutions through the rock to dissolve metals such as copper and uranium. The metal-bearing solutions are pumped to the surface and the metals recovered. Very low grade, small and otherwise economically non-viable deposits can be exploited and the process can be used at considerable depths.
Measures such as recycling and substitution and new materials technology will play their part in reducing the impact of mineral exploitation on the environment, but in the immediate future we have to look to an increasing sense of responsibility by all those involved in any way with the industry, be they developers or regulators.
There are many hopeful signs that this is taking place: for example, in 1992, 19 major mining corporations from five continents joined together to form the international council on metals and the environment whose remit is to promote the development, implementation, and harmonisation of sound environmental and health policies and practices which will ensure the safe production, use, recycling and disposal of metals.