Hemihedrite

Formula:  Pb₁₀Zn(CrO₄)₆(SiO₄)₂F₂

Origin of name:   From Greek hemi - half and hedra - base

Crystal system:  Triclinic

Crystal class:  1

Twinning:  On {-2-23}, {0-12}, or {0-10}

Unit cell: a = 9.50 Ǻ, b = 11.44 Ǻ, c = 10.84 Ǻ, α = 120.5°, β = 92.1°, γ = 55.8°

Colour:  Bright orange to brown to almost black

Diaphaneity: 

Luster:  Vitreous

Habit:  Crystals have triclinic hemihedral symmetry

Hardness:  3

Specific gravity:  6.42

Cleavage:  None

Tenacity: 

Streak:  Saffron yellow

Synonyms/varieties:

Comments:  Series with iranite