Crednerite is a rare copper manganese oxide mineral typically found in oxidized zones of copper deposits. It often occurs as dark, metallic, platy or foliated aggregates and is best identified by its association with other manganese and copper minerals.
Is this crednerite?
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 crednerite with a known reference. Crednerite sits at Mohs 4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: soot-black, with a brownish tint.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: iron black, steel gray.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy, pseudo hexagonal.
Often confused with
Crednerite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Crednerite leaves soot-black, with a brownish tint, Tenorite leaves black.
How to tell apart: Hausmannite is the harder of the two (Mohs 5.5 vs. 4); streak differs, so Crednerite leaves soot-black, with a brownish tint, Hausmannite leaves dark reddish brown; luster reads metallic on Crednerite and submetallic on Hausmannite.
Often found alongside crednerite
Minerals reported to co-occur with crednerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuMnO₂
- Mohs hardness
- 4
- Density
- 4.98-5.34 g/cm³
- Colors
- Streak
- Soot-black, with a brownish tint
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Platy, pseudo hexagonal
- Cleavage
- Perfect parallel to plate surfaces, {001}; also {100}, perfect, {111}, prominent, {111} and {212}, poor
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A low-temperature secondary mineral, perhaps indicating a reducing chemical environment
Where rockhounds find crednerite
Classic worldwide localities
- Bisbee, Cochise Co., Arizona, USA
- Calistoga, Napa Co., California, USA
- Crescent mine, Crescent Lake, Clallam Co., Washington, USA
- Friedrichroda, Thuringia, Germany
- Merehead quarry, near Shepton Mallet, and Higher Pitts Farm, near Priddy, Mendip Hills, Somerset, England
- Långban and Jakobsberg, Värmland, Sweden
Field-hunting tip
Where it forms: A low-temperature secondary mineral, perhaps indicating a reducing chemical environment. If you start seeing psilomelane, hausmannite, malachite in float, you are in the right ground. Typical habit: platy, pseudo hexagonal. Train your eye for that shape before scanning the outcrop.
Common questions
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Find crednerite on the map
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