Cassiterite is the principal ore of tin. It is usually recovered from mines as black opaque grains. These are of little use in jewelry. Crystals are generally short and stubby prisms. Occasionally, rare, transparent, reddish brown crystals with adamantine luster are found and faceted for collectors. They could be confused with diamond, brown zircon, and sphene. However, they have higher specific gravity and distinct dichroism.
The name ‘Cassiterite’ comes from the greek word, kassiteros, meaning tin.
Occurrence
Cassiterite occurs in pegmatites and can be washed into alluvial deposits. Localities include the Malay Peninsula, Germany, England, Namibia, Mexico, Bolivia, and Australia.
Cassiterite Properties
- Specific Gravity: 6.95
- Refractive Index: 2.00-2.10
- Birefringence (DR): 0.100
- Luster: Adamantine
- Crystal Structure: Tetragonal
- Composition: Tin oxide
- Hardness: 6½
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