obsidian

• POS: Noun
• HYPHEN: ob=sid=i=an

CIDE DICTIONARY

obsidian, 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.].

 A kind of glass produced by volcanoes. It is usually of a black color, and opaque, except in thin splinters.  [1913 Webster]
" 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."  [1913 Webster]

OXFORD DICTIONARY

obsidian, n. a dark glassy volcanic rock formed from hardened lava.

Etymology

L obsidianus, error for obsianus f. Obsius, the name (in Pliny) of the discoverer of a similar stone