Definition for OB-SID'I-AN


Glossy lava. A mineral of two kinds, translucent and transparent. The translucent has a velvet black color; the transparent is of a dark blue. These occur massive in porphyry, gneiss or granite, generally invested with a gray opake crust. Dict. Nat. Hist. Ure. Kirwan. The fracture of obsidian is vitreous or pearly; hence the two varieties, vitreous obsidian and pearlstone. Jameson.

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