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. Pradetite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Pradetite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: orange, yellow.
- 5Look at form & habitCrystal system: monoclinic. 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 4-4.5 vs. 3); streak differs — Pradetite leaves yellow, Arseniosiderite leaves yellowish-brown; luster reads vitreous on Pradetite and silky on Arseniosiderite.
How to tell apart: Streak differs — Pradetite leaves yellow, Pharmacosiderite leaves white; luster reads vitreous on Pradetite and adamantine 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
- CoFe₂(AsO₄)₂(OH)₂·8H₂O
- Mohs hardness
- 3
- Density
- 3.37 g/cm³
- Streak
- Yellow
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
- Typical price
- $50-300 per specimen
Where rockhounds find pradetite
Classic worldwide localities
- Pradet, France
Field-hunting tip
Look in hydrothermal veins country — that is the host setting where pradetite typically forms. If you start seeing cobalt-bearing minerals, goethite, arsenates in float, you are in the right ground. Field specimens usually show a platy crystals, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find pradetite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
