Anthonyite is a rare copper halide mineral typically found as small, thin, lavender platy crystals or rosettes. It occurs primarily in the oxidized zones of copper-rich hydrothermal deposits and is prized by micro-mineral collectors for its delicate habit.
Is this anthonyite?
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 anthonyite with a known reference. Anthonyite 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: pale blue.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly.
- 4Match the color rangeCompare against the expected color range: blue, gray violet.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic.
Often confused with
Anthonyite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Connellite is the harder of the two (Mohs 3 vs. 2); luster reads pearly on Anthonyite and vitreous on Connellite.
How to tell apart: Paratacamite is the harder of the two (Mohs 3 vs. 2); streak differs, so Anthonyite leaves pale blue, Paratacamite leaves green; luster reads pearly on Anthonyite and vitreous on Paratacamite.
How to tell apart: Atacamite is the harder of the two (Mohs 3-3.5 vs. 2); streak differs, so Anthonyite leaves pale blue, Atacamite leaves apple-green; luster reads pearly on Anthonyite and adamantine to vitreous on Atacamite.
Often found alongside anthonyite
Minerals reported to co-occur with anthonyite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu(OH)₂·3H₂O
- Mohs hardness
- 2
- Colors
- BlueGray violet
- Streak
- Pale blue
- Luster
- Pearly
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic
- Cleavage
- {100}, good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In cavities and fractures in basalt, formed by the action of chlorine-bearing connate waters on copper (Centennial mine, Michigan, USA)
Where rockhounds find anthonyite
Classic worldwide localities
- Centennial mine, Calumet, Houghton Co., Michigan and the Cole mine, Bisbee, Cochise Co., Arizona, USA
- Villa Hermosa, Sonora, Mexico
- Richelsdorf, Hesse, in slag, Germany
- Laurium, Greece, in slag
Field-hunting tip
Where it forms: In cavities and fractures in basalt, formed by the action of chlorine-bearing connate waters on copper (Centennial mine, Michigan, USA). If you start seeing tremolite, quartz, epidote in float, you are in the right ground. Typical habit: prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
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Find anthonyite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
