Garnet - January birthstone
Published On: 12-14-2011 06:18pm
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Category: Gemstones
Garnet is January’s birthstone.
Garnets are red, right? Not so fast, they actually come in many colors and many names. Colors include red, orange, yellow, green, blue, purple, brown, black, pink and colorless. The rarest of these is the blue garnet. It changes color from blue-green in the daylight to purple in incandescent light.
The names you might hear that fall into the garnet family are almandine, andradite, demantoid, grossularite, hessonite, pyrope, rhodolite, tsavorite, spessartine, and uvarovite. The traditional red is called pyrope.
What makes a garnet a garnet? Well that has to do with a few physical properties including the hardness. Garnets are a 7 to 7.5 on the Mohs scale. Here is a description of some of the different garnets.
Almandine is an iron-aluminium garnet. This red variety is the most commonly used
garnets.
Pyrope meaning "fire-eyed" is red in color and chemically a magnesium aluminium silicate. The magnesium can be replaced in part by calcium and ferrous iron. The color of pyrope varies from deep red to almost black. Transparent pyropes are used as gemstones.
Rhodolite is violet-red shade and has been names for "a rose." In chemical composition it may be considered as essentially a mixture of pyrope and almandine, in the proportion of two parts pyrope to one part almandine.
Spessartine or spessartite is manganese aluminium garnet. Its name is derived from Spessart in Bavaria. Spessartine of an orange-yellow is found in Madagascar. Violet-red spessartines are found in rhyolites in Colorado and Maine.
Andradite is a calcium-iron garnet, is of variable composition and may be red, yellow, brown, green or black. The recognized varieties are topazolite (yellow or green), demantoid (green) and melanite (black). Demantoid has been called the "emerald of the Urals" from its occurrence there, and is one of the most prized of garnet varieties. Topazolite is a golden yellow variety and melanite is a black variety.
Grossular is a calcium-aluminium garnet, though the calcium may in part be replaced by ferrous iron and the aluminium by ferric iron. The name grossular is derived from the botanical name for the gooseberry, grossularia, in reference to the green garnet of this composition that is found in Siberia. Other shades include cinnamon brown (cinnamon stone variety), red, and yellow.
Uvarovite is a calcium chromium garnet. This is a rather rare garnet, bright green in color, usually found as small crystals associated with chromite in peridotite, serpentinite, and kimberlites.
Whatever color you prefer, there’s no denying how beautiful the garnet is and how much we love this gemstone. Pick your color and enjoy!!
Happy Birthday January!!
Shannon
Sources:
http://en.wikipedia.org/wiki/Garnet
http://minerals.usgs.gov/minerals/pubs/commodity/gemstones/sp14-95/garnet.html
