Goethite - Alfa iron oxy Hydroxide
α-FeO(OH)

Crystal system

Orthorhombic 2/m2/m2/m

Color

Yellowish to dark brown

Clavage

Perfect 010

Fracture

uneven to splintery

Mohs scale hardness

5 - 5.5

Specific gravity

3.3 - 3.4

Refractiveindex

Opaque to sub-translucent

Unit Ce4

a =  4.65 Å
b = 10.02 Å
c =  3.04 Å