Beryllium, a lustrous white metal (sp. gr. 2.1, at. wt. 9.1, symbol Be), does not occur free in nature, and it is difficult to obtain the metal from its compounds. It occurs as silicate in phenacite, as aluminate in chrysoberyl, and as silicate together with aluminium silicate in emerald and beryl. Its oxide, BeO. is known as berylla. The metal itself is also called glucinum.