Description
A hard, dense, often glassy, volcanic rock. Basalts are usually dark gray, black, brown, or greenish-black in color and are primarily composed of magnetite and fine-grain silicates such as plagioclase, olivine, and pyroxene. Formed from lava flows, basalts are often found in the form of pillows or columns. Famous natural basalt structures are the Giants Causeway on the northern coast of Ireland, the Needle on St. Helena Island, and Devil's Tower in Wyoming. Black basalts were quarried by ancient Egyptians. These hard stones have been used for building construction and sculptures as well as for small, carved decorative items. Ground basalt is also used to produce glassy, dark-color glazes on pottery.
Synonyms and Related Terms
scoria; Basalt (Dan., Deut., Ned., Nor., Sven.); basalto (Esp., It., Port.); basalte (Fr.); bazalt (Pol.); scoriaceous
Other Properties
usually contains about 50% silica
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Last updated on: 3/10/2010 9:37:56 AM
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