Phenakite is a rare mineral that occurs as white or colorless tabular crystals or stubby prisms. Twinning is common and distinguishes it from rock crystal, with which it is commonly confused. Hence, phenakite is derived from a Greek word for cheat. A transparent phenakite crystal is faceted for collectors and is hard and bright. It has a silvery look when cut well.
A pebble weighing 1,470 carats was found in Sri Lanka, and faceted to a 569-carat oval and several smaller stones. It is essential to note that phenakite crystals have wedge-shaped ends.
Occurrence
Phenakite occurs in pegmatites, granites, and mica schists. The best crystals are found in the Urals (Russia), Colorado (USA), and Brazil. Other localities include Namibia, Sri Lanka, Zimbabwe, and Italy.
Phenakite Properties
- Specific Gravity: 2.96
- Refractive Index: 1.65-1.67
- Birefringence (DR): 0.015
- Luster: Vitreous
- Crystal Structure: Trigonal
- Composition: Beryllium silicate
- Hardness: 7½
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