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 — 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 — that is 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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