Calcurmolite is a rare secondary uranium molybdenum mineral that typically forms bright yellow platy or tabular crystals. It is primarily found as an alteration product in the oxidation zones of uranium-molybdenum ore deposits.
Is this calcurmolite?
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 calcurmolite with a known reference. Calcurmolite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Calcurmolite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Calcurmolite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: yellow, orange-yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, tabular aggregates, coatings.
Often confused with
Calcurmolite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Calcurmolite leaves yellow, Uranophane leaves pale yellow; luster reads pearly on Calcurmolite and vitreous on Uranophane.
How to tell apart: Streak differs — Calcurmolite leaves yellow, Autunite leaves pale yellow.
How to tell apart: Luster reads pearly on Calcurmolite and silky on Molybdite.
Often found alongside calcurmolite
Minerals reported to co-occur with calcurmolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca(UO₂)₃(MoO₄)₃(OH)₂·11H₂O
- Mohs hardness
- 2-3
- Density
- 4.2 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Tabular Aggregates, Coatings
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Uranium-molybdenum Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find calcurmolite
Classic worldwide localities
- Eastern Transbaikalia, Russia
- Kazakhstan
- Kyrgyzstan
Field-hunting tip
Look in oxidized uranium-molybdenum deposits country — that is the host setting where calcurmolite typically forms. If you start seeing uraninite, molybdenite, powellite in float, you are in the right ground. Field specimens usually show a platy crystals, tabular aggregates, coatings habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find calcurmolite on the map
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