answer

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