Beryl

Ber″yl (bĕr″ĭl), n. [F. béryl, OF. beril, L. beryllus, Gr. βήρυλλοσ, prob. fr. Skr. vaiḍūrya. Cf. Brilliant.] (Min.) A mineral of great hardness, and, when transparent, of much beauty. It occurs in hexagonal prisms, commonly of a green or bluish green color, but also yellow, pink, and white. It is a silicate of aluminium and glucinum (beryllium). The aquamarine is a transparent, sea-green variety used as a gem. The emerald is another variety highly prized in jewelry, and distinguished by its deep color, which is probably due to the presence of a little oxide of chromium.