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Obsidian
Obsidian is a naturally occurring volcanic glass formed when lava extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Produced from felsic lava,... Wikipedia
- Category: Volcanic glass
- Color: usually black, sometimes green or brown, rarely yellow, orange, red or blue
- Fracture: Conchoidal
- Mohs scale hardness: 5–6
- Luster: Vitreous
- Specific gravity: c. 2.4
- Optical properties: Translucent
- Melting point: 700 - 1,050 °C (1,292 - 1,922 °F)
- Other characteristics: Texture: Smooth, glassy
- Data Source: DuckDuckGo