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 — 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 — 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 — 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 — that is 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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How much is bayldonite worth?+
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Find bayldonite on the map
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