Hydrobiotite

Occurs in Pinal County.

Chemical Formula: K(Fe₂+/Mg)₃(Si₃Al)O₁₀(OH)₂

Specific Gravity: 2.6-3.3

Luster: Vitreous to pearly

Hardness: 2.5-3.5 Hydrobiotite is a member of the mica group and is a hydrated potassium iron magnesium aluminum silicate mineral. It typically forms platy crystals and is often found in metamorphic rocks.

Next Pinal County mineral: Hydrocerussite