Chemical composition -- Beryllium silicate.
Color -- Colorless or faintly colored by impurities.
Optics -- R.I 1.65-1.67.
Durability -- Hardness 7.5-8. Brittle.
Crystal structure -- Hexagonal.
Specific Gravity -- 2.93-3.00.
Sources -- Phenakite occurs in many locations and may be found in very large pieces; the best sources include Brazil and the Ural Mountains. Finished stones are very brilliant though low in dispersion.