Kermesite is a striking, rare secondary mineral that forms as a result of the alteration of stibnite. It is most easily identified by its vibrant cherry-red, hair-like or tufted crystal sprays that contrast beautifully with matrix rock.
Is this kermesite?
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 kermesite with a known reference. Kermesite sits at Mohs 1-1.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brownish red.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine to semimetallic.
- 4Match the color rangeCompare against the expected color range: cherry red, violet red, red.
- 5Look at form & habitCrystal system: triclinic. Typical habit: acicular, fibrous, radial.
Often confused with
Kermesite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Kermesite leaves brownish red, Stibnite leaves lead-gray; luster reads adamantine to semimetallic on Kermesite and metallic, splendent on cleavage surfaces on Stibnite.
How to tell apart: Streak differs, so Kermesite leaves brownish red, Realgar leaves red-orange to red; luster reads adamantine to semimetallic on Kermesite and resinous to greasy on Realgar.
Often found alongside kermesite
Minerals reported to co-occur with kermesite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Sb₂S₂O
- Mohs hardness
- 1-1.5
- Density
- 4.68 g/cm³
- Colors
- Streak
- Brownish red
- Luster
- Adamantine to semimetallic
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Acicular, fibrous, radial
- Cleavage
- Perfect on {001}; parting on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral, as an alteration of stibnite, in antimony deposits
Where rockhounds find kermesite
Classic worldwide localities
- Braunsdorf, near Freiberg, Saxony, Germany
- Pernek, Pezinok, and PHbram, Czechoslovakia
- Chalanches mine, near Allemont, Isere, France
- Cetine mine, near Siena, Tuscany, Italy
- Kadamdja, Kirgizia, USSR
- Santa Cruz and San Francisco mines, Poopo, Oruro, Bolivia
Field-hunting tip
Where it forms: A secondary mineral, as an alteration of stibnite, in antimony deposits. If you start seeing stibnite, antimony, senarmontite in float, you are in the right ground. Typical habit: acicular, fibrous, radial. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kermesite?+
Where is kermesite found?+
Is kermesite safe to handle?+
What rocks look like kermesite?+
What minerals are found with kermesite?+
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Find kermesite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
