Obsidian
Obsidian is a black volcanic glass. It forms from super-cooled lava. It has been used for some of the earliest tools of humankind.
Type
Rock
Chemical Formula
Non-uniform mixture 70–75% SiO2, with MgO, Fe3O4
Streak
White
Mohs Hardness
5
Color
Usually Black, but highly variable
Luster
Vitreous
Fracture
conchoidal
Description
Obsidian is a black volcanic glass. It forms from super-cooled lava. It has been used for some of the earliest tools of humankind.
Uses
Obsidian is currently used for ornamental purposes, and researchers are investigating the use of obsidian for surgical scalpels in the medical industry.
