Bonattite is a rare copper sulfate mineral that typically forms as an efflorescence in the oxidized zones of copper mines. It is characterized by its pale blue to white fibrous or crust-like habits and is usually found alongside other secondary copper minerals like chalcanthite.
Is this bonattite?
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 bonattite with a known reference. Bonattite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: blue white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous, crystalline crusts, efflorescent aggregates.
Often confused with
Bonattite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Bonattite leaves blue white, Chalcanthite leaves white.
How to tell apart: Brochantite is the harder of the two (Mohs 3.5-4 vs. 2); streak differs, so Bonattite leaves blue white, Brochantite leaves pale green.
How to tell apart: Streak differs, so Bonattite leaves blue white, Epsomite leaves white.
Often found alongside bonattite
Minerals reported to co-occur with bonattite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuSO₄·3H₂O
- Mohs hardness
- 2
- Density
- 2.663 g/cm³
- Colors
- Streak
- Blue white
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous, crystalline crusts, efflorescent aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral in a pyrite deposit (Capo Calamita, Elba, Italy)
Where rockhounds find bonattite
Classic worldwide localities
- Steamboat Hot Springs, Steamboat Springs district, Washoe Co., Nevada, USA
- Recsk copper mine, Mátra Mountains, Hungary
- Avoca claim, Hat Creek, Bonaparte River area, Lillooet district, British Columbia, Canada
- Undu mine, Nukundamu, Vanua Levu, Fiji
- Mina Raua, near Lima, Peru
Field-hunting tip
Where it forms: A secondary mineral in a pyrite deposit (Capo Calamita, Elba, Italy). If you start seeing chalcanthite, pyrite, quartz in float, you are in the right ground. Typical habit: fibrous, crystalline crusts, efflorescent aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
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Find bonattite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
