Formula: Pb6(Ag,Cu)2As4S13
Origin of name: After locality; Lengenbach quarry, Valais, Switzerland
Crystal system: Triclinic
Crystal class: 1 or -1
Twinning: Twin lamellae visible in polished section
Unit cell: a = 18.45 Ǻ, b = 11.68 Ǻ, c = 70.16 Ǻ, α = 90.0°, β = 91.0°, γ = 90.0°
Colour: Steel-gray, tarnishes iridescent
Diaphaneity:
Luster: Metallic
Habit: Crystals thin, blade-shaped, may be curled, flat face striated parallel to elongation
Hardness: 1
Specific gravity: 5.80 to 5.85
Cleavage: 3; One perfect parallel to flat face, two fair across flat face
Tenacity:
Streak:
Synonyms/varieties:
Comments:
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