Bayldonite is a striking secondary copper-lead arsenate mineral most famously occurring as vibrant green, rounded botryoidal coatings. It is typically found in the oxidized zones of arsenic-rich copper-lead deposits, often associated with other rare secondary minerals like mimetite.
Is this bayldonite?
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 bayldonite with a known reference. Bayldonite 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. Streak: green.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous.
- 4Match the color rangeCompare against the expected color range: grass green, yellow green, dark green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: druse, encrustations, mammillary.
Often confused with
Bayldonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Bayldonite leaves green, Mimetite leaves white.
How to tell apart: Streak differs, so Bayldonite leaves green, Duftite leaves pale green to white; luster reads resinous on Bayldonite and dull to vitreous on fractures on Duftite.
How to tell apart: Luster reads resinous on Bayldonite and vitreous to somewhat greasy on Conichalcite.
Often found alongside bayldonite
Minerals reported to co-occur with bayldonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₃PbO(AsO₃OH)₂(OH)₂
- Mohs hardness
- 4.5
- Density
- 5.24-5.65 g/cm³
- Streak
- Green
- Luster
- Resinous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Druse, encrustations, mammillary
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- A rare secondary mineral in the oxidized zone of some polymetallic deposits
Where rockhounds find bayldonite
Classic worldwide localities
- Killie mine, Spruce Mountain district, Elko Co., Nevada, USA
- Bisbee, Cochise Co., and from the Frijole prospect, Santa Rita Mountains, Pima Co., Arizona, USA
- Black Pine mine, near Philipsburg, Granite Co., Montana, USA
- Cornwall, from the Penberthy Croft mine, St. Hilary, England
- Wheal Carpenter, near Gwinear, England
- Wheal Gorland, Gwennap, England
Field-hunting tip
Where it forms: A rare secondary mineral in the oxidized zone of some polymetallic deposits. If you start seeing mimetite, olivenite, azurite in float, you are in the right ground. Typical habit: druse, encrustations, mammillary. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify bayldonite?+
Where is bayldonite found?+
Is bayldonite safe to handle?+
What rocks look like bayldonite?+
What minerals are found with bayldonite?+
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Find bayldonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
