OBSIDIAN

obsidian. Obsidian, a. pertaining to a siege

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Ob‐sid″i‐an (?), n. [[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.) A kind of glass produced by volcanoes. It is usually of a black color, and opaque, except in thin splinters. ☞ 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.