Obsidian

 

Pure obsidian is usually dark in appearance, though the colour varies depending on the presence of impurities. Iron and magnesium typically give the obsidian a dark green to brown to black colour. A very few samples are nearly colourless. In some stones, the inclusion of small, white, radically clustered crystals of cristobalite in the black glass produce a blotchy or snowflake pattern.

 
  Location - USA, Armenia, Turkey, Italy, Mexico, Iceland, Kenya, Greece, New Zealand and Scotland  
Group - Silica R.I. - 1.50 Hardness - 5 - 5.5
   
 

 

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