A hard, dark, glasslike volcanic rock formed by the rapid solidification of lava without crystallization.‘Hard stones such as obsidian and rock crystal were added to the repertoire of the stone-vase maker.’
- ‘The earliest mirrors were of obsidian, a black volcanic rock that could be carved and polished.’
- ‘The presence of basalt and obsidian is a sign of volcanic activity and the instability of the earth's crust in this area.’
- ‘Silent as stones like two black pillars carved from obsidian rock.’
- ‘Obsidian looks like coal and while both are black, obsidian is shinier.’
Early 17th century (as an adjective): from Latin obsidianus, variant of obsianus, from Obsius, the name (in Pliny) of the discoverer of a similar stone.