Mineral Information and Data:

Baumhauerite
Pb12As16S36 [CNMNC approved formula]

Named for Heinrich Adolph Baumhauer (1848-1926), German mineralogist and Professor, University of Fribourg, Switzerland.

IMA status : Valid species (Pre-IMA 1902) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
03.06.13.01  
  (03) Sulfides - Sulfosalts
  (03.06) where 2 < z/y < 2.49 - (A+)i (A++)j [By Cz], A=metals, B=semi-metals, C=non-metals
  (03.06.13)
  
Nickel-Strunz
(10th edition) :
02.HC.05b
  (02) Sulfides
  (02.H) Sulfosalts of SnS Archetype
  (02.HC) With only Pb
  
Crystal system: Triclinic System
Point group (H-M): 1 — pinacoidal
Space group: P1
Unit cell: a = 22.74Å, b = 8.33Å, c = 7.89Å; α = 90.35°, β = 97°, γ = 90.42°
Crystal Habit: Crystals are short prismatic parallel to [010], tabular on {100}; striated on {100} parallel to [010], as well as on {010} parallel to [001]; crystals may be rounded, to 2.5 cm. Also as aggregates of rounded grains.
Twinning: Polysynthetic, on {100}
  
Color: Lead-gray to steel-gray, may tarnish to iridescence
Diaphaneity: Opaque
Luster: Metallic
Hardness (Mohs): 3
Measured Density: 5.33 – 5.44 g/cm3
Cleavage: Perfect on {100}
Fracture: Conchoidal
Streak: Chocolate-brown
  
Geologic Setting: In sugary dolostone (Binntal, Switzerland).
Mineral Association: With baumhauerite-2a, other lead sulfarsenides, realgar, pyrite, dolomite (Binntal, Switzerland)
  

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