Semseyite is a lead antimony sulfosalt known for its distinctive tabular crystals with characteristically curved or serrated edges. It is most frequently encountered in hydrothermal sulfide deposits and is highly prized by collectors for its complex crystal morphology.
Is this semseyite?
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 semseyite with a known reference. Semseyite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic, tarnishes to dull.
- 4Match the color rangeCompare against the expected color range: black, gray.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: radial, spherical, tabular.
Often confused with
Semseyite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Semseyite leaves black, Jamesonite leaves black. grayish.
How to tell apart: Streak differs, so Semseyite leaves black, Boulangerite leaves brownish.
How to tell apart: Streak differs, so Semseyite leaves black, Plagionite leaves blackish lead-gray, deep red-brown.
Often found alongside semseyite
Minerals reported to co-occur with semseyite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₉Sb₈S₂₁
- Mohs hardness
- 2.5
- Density
- 6.03 g/cm³
- Streak
- Black
- Luster
- Metallic, tarnishes to dull
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Radial, spherical, tabular
- Cleavage
- Perfect on {112}
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- In hydrothermal veins formed at medium temperature
Where rockhounds find semseyite
Classic worldwide localities
- Brobdignag prospect, near Silverton, San Juan Co., the Argentine Pass area, Clear Creek Co., and near the Maid of Orleans mine, Montezuma district, Summit Co., Colorado, USA
- Baia Sprie (Felsőbánya) (type locality), at Herja (Kisbánya), in the Baia Mare (Nagybánya) district, and from Rodna, Romania
- Wolfsberg, Harz Mountains, and from the Caspari mine, Arnsberg, North Rhine-Westphalia, Germany
- Les Anglais mine, Massaic, Cantal, France
- Montlucan and Bournac, Montagne Noire, Finistère, France
- Saint-Pons, Alpes-de-Haute-Provence, France
Field-hunting tip
Where it forms: In hydrothermal veins formed at medium temperature. If you start seeing sorbyite, jamesonite, bournonite in float, you are in the right ground. Typical habit: radial, spherical, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify semseyite?+
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Find semseyite on the map
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