Conchoidal fracture
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1 | Obsidian Obsidian is dense volcanic glass, usually rhyolite in composition and typically black in color. Compared with window glass, obsidian is rich in iron and magnesium; tiny (<.005 mm) crystals of iron oxide withinAdd to Reading ListSource URL: www.fs.usda.govLanguage: English - Date: 2011-07-01 20:06:49 |