Garnet, the Gemstone
Taking it's name from the latin "granatum" meaning seed, garnets are a popular semi-precious gemstone found all over the world in a surprising variety of colors. The most common garnet color is a deep, rich, maroon red reminiscent of the the juicy, red seeds of the pomegranate fruit (hence it's name).
Special names have been given to different varieties/colors of the mineral. Rich green tsavorite, golden-to-orange spessartite (spessartine), magenta colored rhodolite, and the Russian demantoid - a rare green stone with a sparkle rivalling (and occasionally surpassing) that of the diamond - are all members of the garnet family. Garnets, especially those of poorer quality, are also called carbuncles.
Garnets are the birthstone for January. It is also considered the gemstone for the 2nd wedding anniversary and sometimes the 6th as well. Rhodolite (a variety of garnet) is sometimes used as an alternate birthstone for the month of June. Garnets have been worn as jewelry since around 3100 BC. They are occasionally mistaken for rubies.
Mineral Properties of the Garnet
Garnets are formed from a complex variety of compounds and elements, which accounts for their highly varied appearance. For chemistry fans, the structure of the garnet is (M2+)3 (M3+)2 (SiO4)3. There are two different groups of garnets, those containing calcium (Ca), which are classified as ugrandite, and those without - known as pyralspite.
Most garnets used in jewelry are in the pyralspite group, which includes:
- Pyrope (Mg)3 (Al)2 (SiO4)3 - the classic deep red garnet, pyrope garnets get their color from the presence of chrome.
- Almandine (almandite) (Fe)3 (Al)2 (SiO4)3 - the darker shades of red and occasionally orange-brown to black, it gets it's color from iron and magnesium. Almandines were popular in Victorian jewelry. Some of them have star inclusions.
- Spessartine (spessartite) (Mn)3 (Al)2 (SiO4)3 - these prized brownish-red to orange garnets contain iron, manganese and aluminum
Some garnets are combinations of these types, such as Rhodolite and Madagascar garnets (amandine and pyrope) and deep purple grape garnets (almandine and spessartite).
The ugrandite group includes the varieties: uvarovite, grossular and andradite garnets.
- Uvarovite(Ca)3 (Cr)2 (SiO4)3 - a type of bright green garnet which occurs as clusters of small, fine crystals, generally not suitable for jewelry
- Grossular (Ca)3 (Al)2 (SiO4)3 - a highly variable type of garnet containing calcium and iron, which includes golden Hessionite and bright green Tsavorite. Tsavorite is a variety of chrome grossular - strikingly intense intense, emerald green garnet that gets it's color from the presence of chromium and/or vanadium. Some types of grossular garnet even resemble jade and have been carved into statues in the same manner.
- Andradite (Ca)3 (Fe)2 (SiO4)3 - a rare and beautiful form of garnet with a prismatic inner structure like that of the diamond, this group includes demantoid garnets. Inclusions of byssolite account for the prized horsetail inclusions found in some demantoid garnets.
Garnets have a hardness ranging from to on the MOHS scale (depending on their individual chemical composition). They form isometric crystals ranging in number of sides (faces) from 8 to as many as 48.
Where are Garnets Found?
Garnets are found in many countries and most continents, including the USA, Russia, Europe, Africa, South America, Sri Lanka, India, Pakistan, Burma, Mexico, Canada and even Scotland! Certain types of garnet are native to particular regions. The beautiful demantoid garnets are from the Ural mountains of Russia, Spessartite is mined mainly in Germany (though it is also found in Africa), Tsavorite is found in Kenya and East Africa.