[uh
b-sid-ee-uhn] 
| a volcanic glass similar in composition to granite, usually dark but transparent in thin pieces, and having a good conchoidal fracture. |
| ob·sid·i·an (ŏb-sĭd'ē-ən) n. A usually black or banded, hard volcanic glass that displays shiny, curved surfaces when fractured and is formed by rapid cooling of lava. [Latin obsidiānus, misreading of obsiānus (lapis), Obsian (stone), obsidian, after Obsius, a Roman who supposedly discovered it or a similar mineral.] |