Volcanic glass (SiO2 rich)Amorphous

Obsidian

Volcanic glass (SiO2 rich)

Mineraloids
Chemical FormulaVolcanic glass (SiO2 rich)
Crystal SystemAmorphous
Mohs Hardness5.5
Specific Gravity2.4
ColorBlack, brown, gray, red
LusterVitreous
StreakWhite
CleavageNone
FractureConchoidal

Occurrence

Natural volcanic glass formed from rapidly cooled lava. Used by ancients for tools and weapons.

Hardness on Mohs Scale

5.5 / 10
Talc (1)Quartz (7)Diamond (10)