Trechmannite is a highly sought-after rare sulfosalt mineral primarily found in the Binnental region of Switzerland. It typically occurs as small, brilliant, deep red tabular crystals within cavities in dolomite, often associated with other rare arsenic-bearing minerals.
Is this trechmannite?
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 trechmannite with a known reference. Trechmannite 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. Streak: scarlet-vermilion.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: scarlet red.
- 5Look at form & habitCrystal system: trigonal. Typical habit: crystalline, prismatic.
Often confused with
Trechmannite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside trechmannite
Minerals reported to co-occur with trechmannite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AgAsS₂
- Mohs hardness
- 1.5-2
- Density
- 4.78 g/cm³
- Colors
- Scarlet red
- Streak
- Scarlet-vermilion
- Luster
- Adamantine
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Crystalline, prismatic
- Cleavage
- Good on {1011}, distinct on {0001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Of hydrothermal origin, in dolostone (Binntal, Switzerland)
Where rockhounds find trechmannite
Classic worldwide localities
- Lengenbach quarry, Binntal, Valais, Switzerland (type locality)
- Niederbeerbach, Odenwald, Hesse, Germany
Field-hunting tip
Where it forms: Of hydrothermal origin, in dolostone (Binntal, Switzerland). If you start seeing seligmannite, tennantite, pyrite in float, you are in the right ground. Typical habit: crystalline, prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify trechmannite?+
Where is trechmannite found?+
Is trechmannite safe to handle?+
What rocks look like trechmannite?+
What minerals are found with trechmannite?+
What kind of rock does trechmannite form in?+
What is trechmannite used for?+
Find trechmannite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
