Cleusonite is a rare member of the crichtonite group found primarily in alpine-type veins in Switzerland. It typically occurs as small, black, tabular rhombohedral crystals characterized by their metallic luster and distinct uranium content.
Is this cleusonite?
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 cleusonite with a known reference. Cleusonite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Cleusonite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Cleusonite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: trigonal. Typical habit: tabular rhombohedral crystals.
Often confused with
Cleusonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads metallic on Cleusonite and submetallic on Manaccanite.
How to tell apart: Streak differs, so Cleusonite leaves black, Iron Ore leaves reddish-brown to black; luster reads metallic on Cleusonite and metallic to submetallic on Iron Ore.
How to tell apart: Luster reads metallic on Cleusonite and submetallic on Crichtonite.
Often found alongside cleusonite
Minerals reported to co-occur with cleusonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Pb,Sr)(U⁴⁺,Fe³⁺,Mn²⁺,Zn)₂(Ti,Fe³⁺,Cr,Sb)₁₈(O,OH)₃₈
- Mohs hardness
- 5-6
- Density
- 4.6-4.9 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Tabular Rhombohedral Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alpine-type Hydrothermal Fissure Veins
- Typical price
- $100-500 per specimen
Where rockhounds find cleusonite
Classic worldwide localities
- Cleuson, Valais, Switzerland
- St. Gotthard Massif, Switzerland
Field-hunting tip
Look in alpine-type hydrothermal fissure veins country, the host setting where cleusonite typically forms. If you start seeing quartz, adularia, anatase in float, you are in the right ground. Field specimens usually show a tabular rhombohedral crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find cleusonite on the map
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