Demantoid Garnet contains titanium and manganese. It is one of the many varieties in the Andradite group of garnets, the other being topazolite and melanite. Demantoid garnet is also the most valuable Andradite that is green. Its color is due to the presence of chromium. It has a higher dispersion than diamond and can be recognized by the characteristic ‘horsetails.’ These are fine, hair-like inclusions of asbestos.
Its crystal face has vitreous to metallic luster.
Occurrence
The best demantoid is found in the Urals in Russia. It is associated with gold-bearing sands and metamorphic rocks. Other localities include northern Italy, Pakistan, Iran, Zaire, and Kenya.
Andradite Garnet Properties
- Specific Gravity: 3.85
- Refractive Index: 1.85-1.89
- Birefringence (DR): None
- Luster: Vitreous to adamantine
- Crystal Structure: Cubic
- Composition: Calcium iron silicate
- Hardness: 6½
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