SiO2 (Al bearing, irradiated)Trigonal

Smoky Quartz

SiO2 (Al bearing, irradiated)

Silicates
Chemical FormulaSiO2 (Al bearing, irradiated)
Crystal SystemTrigonal
Mohs Hardness7
Specific Gravity2.65
ColorBrown to black
LusterVitreous
StreakWhite
CleavageNone
FractureConchoidal

Occurrence

Brown to black variety of quartz. Color caused by natural irradiation of aluminum impurities.

Hardness on Mohs Scale

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