Baumhauerite

Formula:  Pb₃As₄S₉

Origin of name:  For H. Baumhauer (1848-1926), German mineralogist and Professor at University of Fribourg, Switzerland

Crystal system:  Triclinic

Crystal class:  1

Twinning:  On {100}, polysynthetic

Unit cell: a = 22.91 Ǻ, b = 8.33 Ǻ, c = 7.96 Ǻ, α = 90.4°, β = 97°, γ = 90.4°

Colour:  Steel-gray to lead-grey; may tarnish iridescent

Diaphaneity:

Luster:  Metallic

Habit:  Crystals short prismatic or tabular, striated, also as aggregates and rounded grains

Hardness:  3

Specific gravity:  5.33

Cleavage:  1; {100} perfect

Tenacity:  Conchoidal

Streak:  Chocolate brown

Synonyms/varieties:

Comments: found in sugary dolomite with other lead sulfarsenides