Alunite
Chemical Formula	KAl3(SO4)2(OH)6
Species	Sulfates
Crystal System	Trigonal
Mohs Scale	3-4
Specific Gravity	2.6-2.9
Color	Yellow, red, to reddish brown, colorless if pure; may be white, pale shades of gray,
Streak	White
Luster	Vitreous, Pearly
Refractive Index	n = 1.572 n = 1.592
Diaphaneity	Transparent, Translucent
Cleavage	Distinct/GoodOn , distinct; on , traces. Handbook of mineralogy: On , perfect
Fracture	Irregular/Uneven, Splintery, Conchoidal
Crystal Habit：fibrous to columnar, porcelaneous, commonly granular to dense massive
Geological Setting：Formed between 15 C and 400 C by the action of sulfate, which may be generated from pyrite or solfataric action, on aluminous rocks, commonly accompanied by kaolinitization and silicification.