Collection: Staurolite

Formula: Fe²⁺₂Al₉Si₄O₂₃(OH)

The formula can also be considered as alternating layers of kyanite and oxide, and so can be recast as: 4Al₂O[SiO₄]^.AlFe²⁺₂O₄H

Colour: Dark brown, brownish-black, red-brown

Luster: Sub-Vitreous, Resinous

Hardness: 7 - 7½

Specific Gravity: 3.74 - 3.83

Crystal System: Monoclinic

Member of: Staurolite Group