in natural history a genus of imperfect crystals, composed of 12 planes, in an hexangular column, terminated by an hexangular pyramid at one end, and irregularly affixed to some other body at the other, with shorter columns.

There are two species of these crystals; one short, bright, and colourless, found in great plenty in New Spain and other parts of America; the other, a short, dull, and dusky brown one, found in Germany, and sometimes in England.