Basaltes, in Natural History, a heavy hard stone, most commonly black, or greenish, consisting of prismatic crystals, the number of whose sides is uncertain. It is distributed over the whole world, but nowhere exists in greater variety than in Scotland. A celebrated range of columnar basalt exists in Ireland, and is known by the name of the Giant's Causeway. It consists of three piers of three columns, which extend several hundred feet into the sea. These columns are, for the most part, hexagonal, and fit very accurately together, but, generally not adherent to each other, although water cannot penetrate between them. Basaltes, when calcined and pulverized, forms a good substitute for puzzolana, in the composition of hydraulic cement, having the property of hardening under water; and it has also been converted into glass, from which wine bottles have been manufactured.