Halotrichite

Occurs in Pinal County.

Chemical Formula: FeAl₂(SO₄)₄·22H₂O

Specific Gravity: 1.87-1.92

Luster: Vitreous to silky

Hardness: 1.5-2

Halotrichite is a hydrated iron aluminum sulfate mineral that forms as white, silky fibers or crusts. It is found in oxidized sulfide deposits.

Next Pinal County mineral: Hematite