Cotunnite is a rare lead chloride mineral typically forming as a sublimation product at volcanic fumaroles or as an oxidation product of galena. Collectors look for its characteristic adamantine luster and thin, colorless to yellowish orthorhombic crystals. Due to its solubility and lead content, it should be kept in a dry display environment and handled with proper care.
Is this cotunnite?
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 cotunnite with a known reference. Cotunnite 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: white.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine, silky to pearly.
- 4Match the color rangeCompare against the expected color range: white, colorless, green, yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular, massive.
Often confused with
Cotunnite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside cotunnite
Minerals reported to co-occur with cotunnite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- PbCl₂
- Mohs hardness
- 2.5
- Density
- 5.80 g/cm³
- Streak
- White
- Luster
- Adamantine, silky to pearly
- Transparency
- Transparent to opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular, massive
- Cleavage
- Perfect on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A volcanic sublimate or as an alteration of galena in saline environments
Where rockhounds find cotunnite
Classic worldwide localities
- Grand Gulch mine, Grand Wash Cliffs, Bentley district, Mohave Co., Arizona, USA
- Bonanza, Saguache Co., Colorado, USA
- Tintic, Juab Co., Utah, USA
- Loudville mine, Southampton, Hampshire Co., Massachusetts, USA
- Vesuvius, Campania, Italy
- Niccioleta mine, 40 km southwest of Siena, and along Baratti Beach, Tuscany, in slag, Italy
Field-hunting tip
Where it forms: A volcanic sublimate or as an alteration of galena in saline environments. If you start seeing galena, cerussite, anglesite in float, you are in the right ground. Typical habit: acicular, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cotunnite?+
Where is cotunnite found?+
Is cotunnite safe to handle?+
What rocks look like cotunnite?+
What minerals are found with cotunnite?+
What kind of rock does cotunnite form in?+
What is cotunnite used for?+
Find cotunnite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
