Lengenbachite is an exceptionally rare sulfosalt mineral primarily known from the famous Lengenbach locality in the Binntal valley of Switzerland. It typically occurs as thin, lead-gray lath-like or platy crystals embedded within dolomitic marble, often requiring microscopic study for positive identification. It is highly prized by collectors of rare minerals, especially those focused on complex sulfide and sulfosalt assemblages.
Is this lengenbachite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch lengenbachite with a known reference. Lengenbachite sits at Mohs 1.5-2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Lengenbachite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Lengenbachite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: dark lead-gray, black.
- 5Look at form & habitCrystal system: triclinic. Typical habit: thin platy to lath-like crystals, often flexible or foliated.
Often confused with
Lengenbachite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside lengenbachite
Minerals reported to co-occur with lengenbachite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₆Cu₂As₂S₉
- Mohs hardness
- 1.5-2
- Density
- 5.82 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Triclinic
- Crystal habit
- Thin Platy to Lath-like Crystals, Often Flexible or Foliated
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Dolomitic Marble Cavities
- Typical price
- $50-500 depending on specimen size and clarity
Where rockhounds find lengenbachite
Classic worldwide localities
- Lengenbach Quarry, Binntal, Switzerland
Field-hunting tip
Look in dolomitic marble cavities country — that is the host setting where lengenbachite typically forms. If you start seeing realgar, orpiment, sartorite in float, you are in the right ground. Field specimens usually show a thin platy to lath-like crystals, often flexible or foliated habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find lengenbachite on the map
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