Demantoid
Demantoid is the green gemstone variety of the mineral andradite, a member of the garnet group of minerals. Andradite is a calcium- and iron-rich garnet. The chemical formula is Ca3Fe2(SiO4)3 with chromium substitution as the cause of the demantoid green color. Ferric iron is the cause of the yellow in the stone.
| Demantoid | |
|---|---|
Demantoid with stilbite | |
| General | |
| Category | Mineral |
| Formula (repeating unit) | Ca3Fe2Si3O12 |
| Crystal system | cubic |
| Identification | |
| Color | light to deep green |
| Mohs scale hardness | 6.5–7.0 |
| Luster | adamantine |
| Specific gravity | 3.84 |
| Optical properties | Single Refractive |
| Refractive index | 1.880–1.889 |
| Pleochroism | none |
| Dispersion | 0.057 |
| Common impurities | Cr |
It has the misnomers olivine and Uralian emerald.
In approximately 2003, reports began to circulate in the trade that some Russian demantoid garnets were being routinely subjected to heat treatment in order to enhance their color. Such treatment is believed to be performed at relatively low temperatures and is thought not to be detectable by gemological testing.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.