in natural history, a genus of imperfect crystals, with single pyramids; one end of their column being affixed to some solid body. They are dodecahedron, with hexangular columns and hexangular pyramids.

Of these crystals authors enumerate a great many species; among which are the whitish pellucid sprig crystal, a bright brown kind, a dull brown kind, and a bright yellow kind; all which are farther distinguished according to the different lengths of their pyramids.