Cupromolybdite is a rare secondary mineral typically found in the oxidized zones of copper-molybdenum deposits. Collectors should look for vibrant green, tabular crystals or crusts often associated with other copper molybdates like lindgrenite.
Is this cupromolybdite?
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 cupromolybdite with a known reference. Cupromolybdite sits at Mohs ~3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellow to light brown.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: honey-yellow, bright yellow acicular.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular crystals, crusts, massive.
Often confused with
Cupromolybdite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Lindgrenite is the harder of the two (Mohs 4.5 vs. ~3); streak differs, so Cupromolybdite leaves yellow to light brown, Lindgrenite leaves light green; luster reads adamantine on Cupromolybdite and greasy on Lindgrenite.
How to tell apart: Streak differs, so Cupromolybdite leaves yellow to light brown, Euchroite leaves green; luster reads adamantine on Cupromolybdite and vitreous on Euchroite.
How to tell apart: Streak differs, so Cupromolybdite leaves yellow to light brown, Atacamite leaves apple-green.
Often found alongside cupromolybdite
Minerals reported to co-occur with cupromolybdite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₃O(MoO₄)₂
- Mohs hardness
- ~3
- Density
- 4.512 g/cm³
- Colors
- Honey-yellowBright yellow acicular
- Streak
- Yellow to light brown
- Luster
- Adamantine
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular crystals, crusts, massive
- Cleavage
- Distinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A fumarolic mineral formed during post-volcanic degassing
Where rockhounds find cupromolybdite
Classic worldwide localities
- Yadovitaya (poisonous) fumarole, Second Scoria Cone, Tolbachik volcano, Kamchatka Peninsula, Russia
Field-hunting tip
Where it forms: A fumarolic mineral formed during post-volcanic degassing. If you start seeing piypite, fedotovite, vergasovite in float, you are in the right ground. Typical habit: tabular crystals, crusts, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cupromolybdite?+
Where is cupromolybdite found?+
Is cupromolybdite safe to handle?+
What rocks look like cupromolybdite?+
What minerals are found with cupromolybdite?+
What kind of rock does cupromolybdite form in?+
What is cupromolybdite used for?+
Find cupromolybdite on the map
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