Valleriite is a rare copper-iron sulfide mineral known for its striking bronze-brown metallic luster and extremely soft, foliated habit. It is often mistaken for molybdenite or graphite due to its greasy feel and flaky nature, though its specific occurrence in copper-rich ore deposits helps distinguish it.
Is this valleriite?
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 valleriite with a known reference. Valleriite sits at Mohs <1, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic to submetallic.
- 4Match the color rangeCompare against the expected color range: bronze, gray.
- 5Look at form & habitCrystal system: trigonal. Typical habit: massive, nodular.
Often confused with
Valleriite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Valleriite leaves black, Molybdenite leaves bluish gray.
How to tell apart: Pyrrhotite is the harder of the two (Mohs 3.5-4.5 vs. <1); streak differs, so Valleriite leaves black, Pyrrhotite leaves dark grayish black.
Often found alongside valleriite
Minerals reported to co-occur with valleriite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- 2[(Fe,Cu)S]·1.53[(Mg,Al)(OH)₂]
- Mohs hardness
- <1
- Density
- 3.14 g/cm³
- Streak
- Black
- Luster
- Metallic to submetallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Massive, nodular
- Cleavage
- On {0001}, excellent
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- An alteration product of chalcopyrite in chromitites and dunites (Cyprus); in copper-bearing carbonatites, replacing magnetite (Phalaborwa, South Africa)
Where rockhounds find valleriite
Classic worldwide localities
- Elizabeth mine, South Strafford, Strafford Co., Vermont, USA
- Pima mine, near Tucson, Pima Co., and at the Christmas mine, Gila Co., Arizona, USA
- Continental mine, Fierro, Grant Co., New Mexico, USA
- Kopparberg, from the Aurora mine, Ljusnarsberg (type locality), and at Kaveltorp, Sweden
- Transvaal, from the Loolekop carbonatite, Phalaborwa, and at the Mooihoek and Onverwacht pipes, in the Merensky Reef, Bushveld complex, South Africa
- Pefkos, Cyprus
Field-hunting tip
Where it forms: An alteration product of chalcopyrite in chromitites and dunites (Cyprus); in copper-bearing carbonatites, replacing magnetite (Phalaborwa, South Africa). If you start seeing chalcopyrite, cubanite, pyrrhotite in float, you are in the right ground. Typical habit: massive, nodular. Train your eye for that shape before scanning the outcrop.
Common questions
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Find valleriite on the map
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