Dufrenoysite is a rare lead arsenic sulfosalt best known from the famous Lengenbach Quarry in the Binnental, Switzerland. It typically forms sharp, metallic, tabular crystals that often exhibit complex striations and a distinct reddish-brown streak, which helps distinguish it from other lead-gray sulfides.
Is this dufrenoysite?
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 dufrenoysite with a known reference. Dufrenoysite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Dufrenoysite leaves a reddish-brown streak.
- 3Read the lusterHold the specimen under a strong light. Dufrenoysite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: lead-gray, iron-black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, sometimes elongated or striated.
Often confused with
Dufrenoysite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Dufrenoysite leaves reddish-brown, Sartorite leaves chocolate-brown.
How to tell apart: Streak differs, so Dufrenoysite leaves reddish-brown, Gratonite leaves black.
How to tell apart: Streak differs, so Dufrenoysite leaves reddish-brown, Galena leaves lead-gray.
Often found alongside dufrenoysite
Minerals reported to co-occur with dufrenoysite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₂As₂S₅
- Mohs hardness
- 3
- Density
- 5.5-5.6 g/cm³
- Colors
- Streak
- Reddish-brown
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Sometimes Elongated or Striated
- Cleavage
- Good in One Direction
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Dolomitic Marble Cavities
- Typical price
- $50-500 thumbnail, $200-2000 cabinet
Where rockhounds find dufrenoysite
Classic worldwide localities
- Binnental, Switzerland
- Lengenbach Quarry, Switzerland
- Maderanertal, Switzerland
Field-hunting tip
Look in dolomitic marble cavities country, the host setting where dufrenoysite typically forms. If you start seeing realgar, orpiment, sartorite in float, you are in the right ground. Field specimens usually show a tabular crystals, sometimes elongated or striated habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify dufrenoysite?+
Where is dufrenoysite found?+
How much is dufrenoysite worth?+
Is dufrenoysite safe to handle?+
What rocks look like dufrenoysite?+
What minerals are found with dufrenoysite?+
What kind of rock does dufrenoysite form in?+
What is dufrenoysite used for?+
Find dufrenoysite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
