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. Streak: yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly.
- 4Match the color rangeCompare against the expected color range: honey yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, prismatic.
Often confused with
Calcurmolite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Calcurmolite leaves yellow, Uranophane leaves yellowish white; luster reads pearly on Calcurmolite and vitreous on Uranophane.
How to tell apart: Streak differs, so Calcurmolite leaves yellow, Autunite leaves pale yellow; luster reads pearly on Calcurmolite and vitreous, pearly on {001} on Autunite.
How to tell apart: Streak differs, so Calcurmolite leaves yellow, Molybdite leaves white; luster reads pearly on Calcurmolite and adamantine 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
- Ca₂(UO₂)₃(MoO₄)₂(OH)₆·4-9H₂O
- Mohs hardness
- 2-3
- Density
- 4.2 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Massive, prismatic
- Cleavage
- Perfect basal
- Fluorescence
- Bright yellow green under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral in the lower oxidized zone of Mo–U deposits
Where rockhounds find calcurmolite
Classic worldwide localities
- Kadzharan molybdenum deposit, upper Okhcha River, Kafan district, Armenia
- Kyzylsai Mo–U deposit, Chu-Ili Mountains, southwestern Balkhash region, Kazakhstan
- Tongbiguan village, Yingjiang Co., Yunnan Province, China
- Rabéjac and Mas-d’Alary uranium deposits, south of Lodève, Hérault, France
Field-hunting tip
Where it forms: A secondary mineral in the lower oxidized zone of Mo–U deposits. If you start seeing uraninite, uranophane, uranospinite in float, you are in the right ground. Typical habit: massive, prismatic. 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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