Category:Obsidian

Ob*sid"i*an, n. Etym: [l. Obsidianus lapis, so named, according to Pliny, after one obsidius, who discovered it in ethiopia: cf.F. Obsidiane, obsidienne. The later editions of pliny read obsianus Lapis, and obsius, instead of obsidianus lapis, and obsidius.] (min.)

Defn: a kind of glass produced by volcanoes. It is usually of a black Color, and opaque, except in thin splinters.

Note: in a thin section it often exhibits a fluidal structure, marked By the arrangement of microlites in the lines of the flow of the Molten mass.