Comblainite is a rare nickel-cobalt carbonate mineral occurring as small, delicate platy crystals or thin crusts. It is typically found in weathered limestone environments and is highly prized by collectors for its distinct, vibrant yellow to brownish-turquoise-blue color and rarity.
Is this comblainite?
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 comblainite with a known reference. Comblainite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellowish-white.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly.
- 4Match the color rangeCompare against the expected color range: blue, turquoise.
- 5Look at form & habitCrystal system: trigonal. Typical habit: encrustations.
Often confused with
Comblainite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Comblainite leaves yellowish-white, Hydrotalcite leaves white; luster reads pearly on Comblainite and satiny to greasy or waxy on Hydrotalcite.
How to tell apart: Streak differs, so Comblainite leaves yellowish-white, Stichtite leaves very pale lilac to white; luster reads pearly on Comblainite and waxy to resinous, somewhat pearly on Stichtite.
Often found alongside comblainite
Minerals reported to co-occur with comblainite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ni₄Co₂(OH)₁₂(CO₃)·3H₂O
- Mohs hardness
- 2
- Density
- 3.05 g/cm³
- Streak
- Yellowish-white
- Luster
- Pearly
- Transparency
- Semitransparent
- Crystal system
- Trigonal
- Crystal habit
- Encrustations
- Cleavage
- Perfect basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An alteration product of nickel and cobalt sulfides in the oxidized zone of a uranium deposit
Where rockhounds find comblainite
Classic worldwide localities
- Shinkolobwe, Katanga Province, Congo (Shaba Province, Zaire)
Field-hunting tip
Where it forms: An alteration product of nickel and cobalt sulfides in the oxidized zone of a uranium deposit. If you start seeing uraninite, metasaleeite, uranophane in float, you are in the right ground. Typical habit: encrustations. Train your eye for that shape before scanning the outcrop.
Common questions
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Find comblainite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
