|Finest Red Garnet
If you look at a gemological reference on garnet, you'll see that there are 6 different members of the garnet group: pyrope, almandite, spessartite, grossularite, andradite and uvarovite. All of these have a similar crystal structure, but they vary slightly in their chemical composition.
In the real world natural garnets rarely match the specifications for these types exactly. In fact varietal names have been given to some garnets of intermediate composition. For example, the garnet with a composition halfway between spessartite and pyrope is known as malaia. Another example is rhodolite garnet, which has a chemical composition averaging a 2:1 mixture of pyrope to almandite.
Rhodolite is interesting not only for its chemical composition, but for its unique color. It is a red garnet, but very different from the familiar deep brownish-red of ordinary red garnet. Rhodolite's name comes from the Greek rhodon meaning rose, and its color ranges from rose red to raspberry red, purple-red and purple-pink.
One of the interesting facts about rhodolite garnet is that it was first discovered in the United States, in the state of North Carolina, around 1898. Even more interesting, it was discovered by mineralogist W.E. Hidden, who also discovered hiddenite, the green variety of spodumene which bears his name.
North Carolina is no longer a significant source for rhodolite. Today the major commercial deposits are in Sri Lanka, Brazil, Zimbabwe, Tanzania, Kenya, Mozambique, Madagascar, and India. Most of the high quality material we've seen recently here in Thailand comes from East Africa.
We have recently cut some fine rhodolite rough from Mozambique and Tanzania, including some unusual large pieces that are rarely found. These have excellent color saturation and clarity. We've cut dozens of pieces around 10 carats, and a few pieces over 30 carats, including one remarkable 96 carat gem.
Since garnet has a hardness of 7 to 7.5 on the Mohs scale, and indistinct cleavage, it is a durable gemstone that is suitable for all kinds of jewelry. Rhodolite garnet has a high refractive index -- in fact slightly higher than sapphire and ruby -- so it it has excellent brilliance. Rhodolite is one of the more expensive garnets, falling between common red garnet and spessartite in price. But rhodolite, like other garnets, is always untreated. So given the stunning color and its very good gemstone characteristics, we think rhodolite is a superb value in today's gemstone market.
- First Published: March-27-2008
- Last Updated: October-07-2010
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