Andradite
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Description
A type of Garnet composed of a calcium iron silicate. The color of andradite may be yellow, red, green, brown or black. Bright green andradite, or demantoid, is also called the emerald of the Urals. Gemstone quality andradite is mined in the Ural Mountains, Italy, Switzerland, Norway, France, and in the United States (Arkansas and New Jersey).
Synonyms and Related Terms
garnet; demantoid (green, emerald of the Urals); topazolite (yellow); melanite (brown or black); andradita (Esp.); andradite (Port.); Andradit (Deut.); andradiet (Ned.)
Physical and Chemical Properties
- Cubic crystal system with dodecahedra/trapezohedra combinations or granular to massive crystals
- Cleavage = none
- Fracture = conchoidal to uneven
- Luster = vitreous to resinous
- Streak = colorless to white
- Dispersion = 0.057
- Fluorescence = inert
- Pleochroism = none
- Birefringence = none
| Composition | Ca3Fe2Si3O12 |
|---|---|
| Mohs Hardness | 6.5 - 7.0 |
| Density | 3.8 - 3.9 g/ml |
| Refractive Index | 1.887 |
Comparisons
Resources and Citations
- Mineralogy Database: Andradite
- Gem Identification Lab Manual, Gemological Institute of America, 2016.
- Wikipedia: Andradite (Accessed Dec 2022)
- G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971
- Encyclopedia Britannica, http://www.britannica.com Comment: andradite [Accessed May 20, 2003].
- C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979