Chrysoberyl

Chrysoberyl, an oxide of aluminium and beryllium (Al₂0₃BeO). occurring as a transparent green gem. It crystallises in the prismatic system, often in six-sided or stellate twins; has a vitreous lustre and a colourless streak, and is unaffected by acids, and with great difficulty fusible even with fluxes. Hardness = 8.5. Specific gravity = 3.6 to 3.8. A yellowish variety is known as oriental chrysolite; one with internal chatoyance is known as cymophane; and one green by sunlight and red by candle-light, as alexandrite.