At 11:59 AM 11/13/96 +0000, you wrote:
Richard O. Martin wrote:
In the unlikely event you don’t know what Tsavorite/Tsavolite is, it’s an
emerald-green grossular garnet mainly from Kenya near the Tanzanian border.<
Gavin Gilmore wrote:
Have heard the name Demontoid Garnet used I believe for the same
I never have, but if someone did it would be wrong. They’re both green
garnets, but that’s where the similarity ends. Tsavorite is a grossular
garnet colored green by vanadium. It is produced mainly in Africa and is
scarce. Demantoid, on the other hand, is andradite garnet originally
discovered in 1868 in Russia’s Ural Mountains. It was the first green
garnet recorded in gemological literature, and instead of being scarce, it’s
downright rare (unless reports I’ve read recently of a new source in "Asia"
turn out to be true). Whereas Tsavorite/Tsavolite have enough production to
allow wide-scale marketing, demantoid has been a rare collector stone,
recognized by it’s typical “horsetail” inclusions of byssolite. The
grass-green color is caused by traces of chromium in combination with iron.
The stone’s name was taken from the Dutch word for diamond, "demant,“
because of its very high (for a colored stone) refractive index, and because
it’s ability to break white light into spectral colors (called dispersion or
"fire”) exceeds that of diamond.
There’s another green garnet, uvarovite, seen these days mostly as drusy
material from Russia. It’s also colored by chromium. It would be a very
valuable gem if it occurred in large sizes, but it doesn’t – so far (new
garnets have a way of cropping up, like the new Mali garnet which is a
previously unknown combination of andradite and spessartite).
Hope this helps.