Arthurite is a rare secondary copper arsenate mineral typically found in the oxidized zones of copper deposits. It usually forms small, vibrant apple-green acicular crystal sprays or coatings associated with other secondary copper minerals. Because of its rarity and striking color, it is a highly sought-after species for mineral collectors.
Is this arthurite?
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 arthurite with a known reference. Arthurite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: light green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: apple green, emerald green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular, prismatic, spherical.
Often confused with
Arthurite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Arthurite leaves light green, Chenevixite leaves greenish yellow; luster reads vitreous on Arthurite and greasy on Chenevixite.
How to tell apart: Streak differs, so Arthurite leaves light green, Cornwallite leaves pale green.
Often found alongside arthurite
Minerals reported to co-occur with arthurite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CuFe₂(AsO₄)₂(OH)₂·4H₂O
- Mohs hardness
- 3-4
- Density
- 3.02 g/cm³
- Colors
- Streak
- Light green
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular, prismatic, spherical
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral in the oxidized zone of some copper deposits, formed by alteration of arsenopyrite or enargite
Where rockhounds find arthurite
Classic worldwide localities
- Majuba Hill mine, Antelope district, Pershing Co., Nevada, USA
- Black Pine mine, near Philipsburg, Granite Co., Montana, USA
- Gold Hill, Tooele Co., Utah, USA
- Cornwall, from the Hingston Down Consols mine, Calstock, the Gunheath china clay pit, St. Austell, and the Cligga Head mine, Perranzabuloe, England
- Clara mine, near Oberwolfach, Black Forest, Germany
- Bendada pegmatite, near Guarda, Portugal
Field-hunting tip
Where it forms: A rare secondary mineral in the oxidized zone of some copper deposits, formed by alteration of arsenopyrite or enargite. If you start seeing pharmacosiderite, scorodite, conichalcite in float, you are in the right ground. Typical habit: acicular, prismatic, spherical. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify arthurite?+
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Find arthurite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
