Chalcanthite is a striking, deep blue secondary mineral typically found in the oxidized zones of copper deposits. It is famous for forming vibrant, crust-like aggregates or delicate, needle-like crystals, though it is highly fragile and readily dissolves in water.
Is this chalcanthite?
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 chalcanthite with a known reference. Chalcanthite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Chalcanthite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Chalcanthite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: blue, blue-green.
- 5Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals, massive, stalactitic, fibrous crusts.
Often confused with
Chalcanthite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Azurite is the harder of the two (Mohs 3.5-4 vs. 2.5); streak differs, so Chalcanthite leaves white, Azurite leaves light blue; luster reads vitreous on Chalcanthite and vitreous to dull on Azurite.
How to tell apart: Turquoise is the harder of the two (Mohs 5-6 vs. 2.5); luster reads vitreous on Chalcanthite and waxy on Turquoise.
How to tell apart: Antlerite is the harder of the two (Mohs 3.5 vs. 2.5); streak differs, so Chalcanthite leaves white, Antlerite leaves light green.
Often found alongside chalcanthite
Minerals reported to co-occur with chalcanthite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuSO₄·5H₂O
- Mohs hardness
- 2.5
- Density
- 2.28 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Tabular Crystals, Massive, Stalactitic, Fibrous Crusts
- Cleavage
- Imperfect
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Oxidized Zones of Copper Ore Deposits
- Typical price
- $10-100 per specimen
Where rockhounds find chalcanthite
1 mapped spotsClassic worldwide localities
- Chuquicamata Mine, Chile
- Rio Tinto, Spain
- Bisbee, Arizona, USA
- Mount Isa, Australia
Field-hunting tip
Look in oxidized zones of copper ore deposits country, the host setting where chalcanthite typically forms. If you start seeing brochantite, melanterite, cuprite in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, stalactitic, fibrous crusts habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Nevada. Start trip planning there.
Common questions
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Find chalcanthite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
