Pradetite is a rare cobalt-bearing arsenate mineral named after its type locality near Pradet, France. It typically occurs as delicate, orange-to-yellow crystalline crusts or small platy aggregates in oxidized zones of ore deposits. Collectors primarily seek it as a rare species of interest for systematic mineral suites.
Is this pradetite?
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 pradetite with a known reference. Pradetite 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.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: orange, yellow.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy crystals, crusts.
Often confused with
Pradetite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Arseniosiderite is the harder of the two (Mohs 4.5 vs. 3); streak differs, so Pradetite leaves yellow, Arseniosiderite leaves ocher-yellow; luster reads vitreous on Pradetite and submetallic to silky on Arseniosiderite.
How to tell apart: Streak differs, so Pradetite leaves yellow, Pharmacosiderite leaves yellowish green; luster reads vitreous on Pradetite and adamantine to greasy on Pharmacosiderite.
Often found alongside pradetite
Minerals reported to co-occur with pradetite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CoCu₄(AsO₄)₂(AsO₃OH)₂(H₂O)₈·H₂O
- Mohs hardness
- 3
- Streak
- Yellow
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Platy crystals, crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- hydrothermal veins
Where rockhounds find pradetite
Classic worldwide localities
- Pradet, France
Field-hunting tip
Where it forms: hydrothermal veins. If you start seeing cobalt-bearing minerals, goethite, arsenates in float, you are in the right ground. Typical habit: platy crystals, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
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Find pradetite on the map
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