Demesmaekerite is a rare secondary mineral typically found as small, bottle-green to pale olive-green needles or blades. It is known primarily from the uranium-rich oxidation zones of the Katanga copper belt in the Democratic Republic of the Congo.
Is this demesmaekerite?
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 demesmaekerite with a known reference. Demesmaekerite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellowish.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: bottle green, brown, brownish green, green.
- 5Look at form & habitCrystal system: triclinic. Typical habit: aggregates.
Often confused with
Demesmaekerite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Demesmaekerite is noticeably harder (Mohs 3-4 vs. 2); streak differs, so Demesmaekerite leaves yellowish, Guilleminite leaves yellow.
How to tell apart: Derbylite is the harder of the two (Mohs 5 vs. 3-4); streak differs, so Demesmaekerite leaves yellowish, Derbylite leaves brownish black; luster reads vitreous on Demesmaekerite and resinous to metallic on Derbylite.
Often found alongside demesmaekerite
Minerals reported to co-occur with demesmaekerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₂Cu₅(UO₂)₂(SeO₃)₆(OH)₆·2H₂O
- Mohs hardness
- 3-4
- Density
- 5.28 g/cm³
- Colors
- Streak
- Yellowish
- Luster
- Vitreous
- Transparency
- Translucent to opaque
- Crystal system
- Triclinic
- Crystal habit
- Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Rare in the lower oxidized portions of a selenium-bearing Cu–Co deposit
Where rockhounds find demesmaekerite
Classic worldwide localities
- Musonoi Co–Cu mine, near Kolwezi, Katanga Province, Congo (Shaba Province, Zaire)
Field-hunting tip
Where it forms: Rare in the lower oxidized portions of a selenium-bearing Cu–Co deposit. If you start seeing cuprosklodowskite, kasolite, guilleminite in float, you are in the right ground. Typical habit: aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify demesmaekerite?+
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What rocks look like demesmaekerite?+
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Find demesmaekerite on the map
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