• dark, black
• smooth surface
• glassy luster, vireous
• called "nature's glass"
• breaks with a sharp conchoidal fracture
• formed during slow cooling of lava
   

Obsidian Varieties

• there are many varieties named after the appearance of obsidian
• the variety is caused by the chemical mixture of the magma when it cooled, its chemical composition

This is an obsidian chunk that has been tumbled about. Notice the dull, gray exterior and the roundness of the piece. Where the rock is freshly broken, the colour is bright and the surface looks shiny, glass-like.
 

Apache Tears