n. 黑曜石

[ noun ]
acid or granitic glass formed by the rapid cooling of lava without crystallization; usually dark, but transparent in thin pieces
<noun.substance>

obsidian \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.

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.