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. Bayldonite leaves a pale green streak.
- 3Read the lusterHold the specimen under a strong light. Bayldonite typically shows a vitreous to greasy luster.
- 4Match the color rangeCompare against the expected color range: apple green, grass green, bright green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: botryoidal, crusts, or small crystalline aggregates.
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 pale green, Mimetite leaves white; luster reads vitreous to greasy on Bayldonite and adamantine on Mimetite.
How to tell apart: Bayldonite is noticeably harder (Mohs 4.5 vs. 3.5); streak differs, so Bayldonite leaves pale green, Duftite leaves light green; luster reads vitreous to greasy on Bayldonite and vitreous on Duftite.
How to tell apart: Streak differs, so Bayldonite leaves pale green, Conichalcite leaves light green; luster reads vitreous to greasy on Bayldonite and vitreous 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
- PbCu₃(AsO₄)₂(OH)₂
- Mohs hardness
- 4.5
- Density
- 5.68 g/cm³
- Streak
- Pale Green
- Luster
- Vitreous to Greasy
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Botryoidal, Crusts, Or Small Crystalline Aggregates
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Oxidized Zones of Polymetallic Hydrothermal Ore Deposits
- Typical price
- $20-150 thumbnail
Where rockhounds find bayldonite
Classic worldwide localities
- Tsumeb Mine, Namibia
- Cornwall, England
- Mapimi, Mexico
- Touissit, Morocco
Field-hunting tip
Look in oxidized zones of polymetallic hydrothermal ore deposits country, the host setting where bayldonite typically forms. If you start seeing mimetite, cerussite, malachite in float, you are in the right ground. Field specimens usually show a botryoidal, crusts, or small crystalline aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find bayldonite on the map
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