Garnets are actually a group of minerals that have a lot in common. As the world becomes more and more gem-savvy, more people are coming to know the wonders of garnet.
First of all, garnets are all silicate minerals and crystallize in the isometric crystal system (also known as the cubic crystal system). The most common crystal form within the isometric system in which Garnets form is a “rhombic dodecahedron:” a 12 sided form that is somewhat of a cube with fanciful flourishes. While a true cube has 6 sides, garnets add another 6 just for fun.
Another fact not everyone is aware of is that garnets come in many colors. In its guise as January’s birthstone, garnet has been traditionally thought of as red. It is true that the greatest number of garnets are red, but it is also true that garnets come in a veritable rainbow of colors.
This bit of knowledge regarding the color spectrum was not true 39 years ago when I first ventured into the world of gems. Due to my father’s interest in gems and minerals I knew at a young age that the Spessartite variety of garnet comes in orange and that Demantoid garnet is green.
Nearly four decades later, gemologist throughout the USA, Europe and Japan recognize that the word “garnet” indicates a variety of colors, however adding to the confusion during this same time period are the recognition of additional varieties of garnet. We’ll describe them below:
Just a few years before I ventured into the gem field, tsavorite garnet had been discovered in Kenya, East Africa. Tsavorite was originally thought to be colored by chromium since it is green and the only previously known green garnet was Demantoid which is colored by chromium. As it turns out Tsavorite is colored by vanadium. Which brings up a new subject…
While garnets are all silicate minerals—they all have SiO4 in common—the colors of garnets and the definition of each type of garnet depends on small quantities of additional elements. This is where we get all the color varieties. Tsavorite is a color variety of grossularite garnet. In addition to the green color there are grossularite gems from the same region varying from colorless through gradations of yellow into orange and further into orangey-red and colorless through very pale green into medium green and further into dark green.
Color Change Garnets
More recently found in East Africa are color changing garnets which have color changing properties similar to that of alexandrite. Similar color changing garnets have also been found in Sri Lanka. The color changes from daylight (green or blue) to night light (purple or mauve or reddish purple). Large fine examples of this gem can run into the tens of thousands of dollars.
Spessartite is a completely different and separate type of garnet is known for a bright vivid orange color. There is some argument amongst gem aficionados as to the best color for Spessartite having to do with the amount or lack of red in the orange color. One thing that is not under debate is the fact that the high refractive index of Spessartite helps give the stone its own distinctive bright luster. On a comparative basis with red garnets Spessartite is rare especially in large sizes. This rarity along with its beauty brings considerably high prices for Spessartite in those larger sizes.
Rhodolite garnet is one of the most lovely of the red garnets. Rhodolite was originally described scientifically from finds in North Carolina. It is a cross-pollination (pardon the use of a botanical term) of pyrope and almandine. Rhodolite in its finest form is a pinkish red and can even be confused with rubellite tourmaline due to its fine color. There has been debate about the origin of the name. Some people say the rhododendron flowers found in North Carolina gave Rhodolite its name. Others say the name came from the Greek with a reference to rose-like. In either case Rhodolite is the flower of the red garnets.