Chalcosiderite is a rare copper-iron phosphate mineral that typically forms as attractive, vibrant green to yellow-green crusts or botryoidal coatings. Collectors prize it for its brilliant color, though it is often found in small quantities associated with secondary oxidation zones in copper mines.
Is this chalcosiderite?
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 chalcosiderite with a known reference. Chalcosiderite sits at Mohs 4.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Chalcosiderite leaves a light green streak.
- 3Read the lusterHold the specimen under a strong light. Chalcosiderite typically shows a vitreous to greasy luster.
- 4Match the color rangeCompare against the expected color range: green, yellow-green, blue-green.
- 5Look at form & habitCrystal system: triclinic. Typical habit: botryoidal, crusts, or small prismatic crystals.
Often confused with
Chalcosiderite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Chalcosiderite leaves light green, Turquoise leaves white; luster reads vitreous to greasy on Chalcosiderite and waxy on Turquoise.
How to tell apart: Streak differs — Chalcosiderite leaves light green, Variscite leaves white; luster reads vitreous to greasy on Chalcosiderite and waxy on Variscite.
How to tell apart: Streak differs — Chalcosiderite leaves light green, Wavellite leaves white; luster reads vitreous to greasy on Chalcosiderite and vitreous on Wavellite.
Often found alongside chalcosiderite
Minerals reported to co-occur with chalcosiderite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuFe³⁺₆(PO₄)₄(OH)₈·4H₂O
- Mohs hardness
- 4.5
- Density
- 3.37-3.41 g/cm³
- Streak
- Light Green
- Luster
- Vitreous to Greasy
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Botryoidal, Crusts, Or Small Prismatic Crystals
- Cleavage
- Good in One Direction
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Copper-bearing Ore Deposits
- Typical price
- $20-150 for small cabinet specimens
Where rockhounds find chalcosiderite
Classic worldwide localities
- Cornwall, England
- Arizona, USA
- New Mexico, USA
- Germany
Field-hunting tip
Look in oxidized zones of copper-bearing ore deposits country — that is the host setting where chalcosiderite typically forms. If you start seeing goethite, pyrite, cuprite in float, you are in the right ground. Field specimens usually show a botryoidal, crusts, or small prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify chalcosiderite?+
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Find chalcosiderite on the map
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