Pseudoboleite is a rare lead-copper halide typically found as deep blue, pseudocubic crystals. It is most famously associated with the Boleo district in Mexico, where it forms in oxidized hydrothermal veins alongside other secondary copper minerals.
Is this pseudoboleite?
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 pseudoboleite with a known reference. Pseudoboleite sits at Mohs 2.5, 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: pearly on cleavages.
- 4Match the color rangeCompare against the expected color range: indigo blue.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: pseudo cubic.
Often confused with
Pseudoboleite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Pseudoboleite leaves light green, Boleite leaves blue, with greenish tint; luster reads pearly on cleavages on Pseudoboleite and weakly vitreous; pearly on cleavage surfaces on Boleite.
How to tell apart: Streak differs, so Pseudoboleite leaves light green, Cumengeite leaves sky-blue; luster reads pearly on cleavages on Pseudoboleite and weakly vitreous to adamantine on Cumengeite.
How to tell apart: Streak differs, so Pseudoboleite leaves light green, Diaboleite leaves pale blue; luster reads pearly on cleavages on Pseudoboleite and adamantine, pearly on cleavages on Diaboleite.
Often found alongside pseudoboleite
Minerals reported to co-occur with pseudoboleite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₃₁Cu₂₄Cl₆₂(OH)₄₈
- Mohs hardness
- 2.5
- Density
- 4.85 g/cm³
- Colors
- Indigo blue
- Streak
- Light green
- Luster
- Pearly on cleavages
- Transparency
- Translucent
- Crystal system
- Tetragonal
- Crystal habit
- Pseudo cubic
- Cleavage
- {001}, perfect; {101}, nearly perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral formed through reaction of chloride with primary sulfides in the oxidized zone of Pb–Cu deposits; in smelter slag immersed in and leached by sea water
Where rockhounds find pseudoboleite
Classic worldwide localities
- Mammoth-St. Anthony mine, Tiger, Pinal Co., and the Banner mine, Pima Co., Arizona, USA
- Amelia mine, Boleo, near Santa Rosalía, Baja California, and from an undefined locality in Sonora, Mexico
- Laurium, Greece, in slag
- Tolcarne Beach, Newquay, Cornwall, England
- Mantos Blancos, and at several mines around Caracoles, Sierra Gorda district, Antofagasta, Chile
- Chancay, Peru
Field-hunting tip
Where it forms: A secondary mineral formed through reaction of chloride with primary sulfides in the oxidized zone of Pb–Cu deposits; in smelter slag immersed in and leached by sea water. If you start seeing boleite, cumengeite, atacamite in float, you are in the right ground. Typical habit: pseudo cubic. Train your eye for that shape before scanning the outcrop.
Common questions
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Find pseudoboleite on the map
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