Image: James St. John (CC BY 2.0)
amorphouscommonVolcanic Glass (Igneous Rock)
Obsidian
SiO2 (amorphous)
A piece of green obsidian exhibiting a characteristic conchoidal fracture surface, indicative of its glassy texture. The color is a deep, translucent green.
Obsidian Physical Properties
Mohs Hardness
5Crystal System
amorphousLuster
vitreousStreak Color
whiteCleavage
noneFracture
conchoidalSpecific Gravity
2.35Colors
black, brown, green, red, gray, iridescentTransparency
opaqueType Locality
MexicoMineral Group
Volcanic Glass (Igneous Rock)Uses
jewelry, ancient tools and weapons, ornamental objects, collector's itemAssociated Minerals
Rarity
commonGeological Context
Obsidian is an extrusive igneous rock that forms from the rapid cooling of highly viscous, silica-rich lava, which prevents the formation of crystalline structures, resulting in a natural glass.
