Barstowite is a rare lead chloride carbonate mineral that typically forms as sharp, prismatic crystals in oxidized lead deposits. It is most famously found in the slag dumps of the Barstow mine in England and at the ancient mines of Laurium, Greece, often associated with phosgenite.
Is this barstowite?
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 barstowite with a known reference. Barstowite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: microscopic crystals, prismatic.
Often confused with
Barstowite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside barstowite
Minerals reported to co-occur with barstowite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₄Cl₆(CO₃)·H₂O
- Mohs hardness
- 3
- Density
- 5.71 g/cm³
- Streak
- White
- Luster
- Adamantine
- Transparency
- Transparent to opaque
- Crystal system
- Monoclinic
- Crystal habit
- Microscopic crystals, prismatic
- Cleavage
- Prismatic, imperfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare reaction product of sea water with a metal-bearing vein exposed at sea level (Bounds Cliff, England); produced by the action of sea water on lead-bearing slag (Laurium, Greece; Baratti Beach, Italy)
Where rockhounds find barstowite
Classic worldwide localities
- Bounds Cliff, St. Endellion, Cornwall, England
- Laurium, Greece, in slag
- Baratti Beach, Tuscany, Italy, in slag
- Kairakty polymetallic barite deposit, central Kazakhstan
- A shipwreck near Mahdia, Tunisia
Field-hunting tip
Where it forms: A rare reaction product of sea water with a metal-bearing vein exposed at sea level (Bounds Cliff, England); produced by the action of sea water on lead-bearing slag (Laurium, Greece; Baratti Beach, Italy). If you start seeing phosgenite, galena, jamesonite in float, you are in the right ground. Typical habit: microscopic crystals, prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify barstowite?+
Where is barstowite found?+
Is barstowite safe to handle?+
What rocks look like barstowite?+
What minerals are found with barstowite?+
What kind of rock does barstowite form in?+
What is barstowite used for?+
Find barstowite on the map
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