Pseudocotunnite is a rare lead potassium chloride mineral typically formed by volcanic sublimation. It is most frequently encountered as yellow to colorless acicular or fibrous crystals forming crusts in active or dormant volcanic fumaroles.

Hardness

2-3

Mohs

Luster

Adamantine

Streak

White

Transparency

Translucent

mineralrare

Pseudocotunnite

Hardness: 2-3
Luster: Adamantine
Streak: White
Transparency: Translucent

Is this pseudocotunnite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch pseudocotunnite with a known reference. Pseudocotunnite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Pseudocotunnite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Pseudocotunnite typically shows a adamantine luster.
4
Match the color range
Compare against the expected color range: yellow, white, colorless.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: acicular crystals, fibrous, encrustations.

Often confused with

Pseudocotunnite vs. its common look-alikes — and how to tell them apart in the field.

Often found alongside pseudocotunnite

Minerals reported to co-occur with pseudocotunnite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: K₂PbCl₄
Mohs hardness: 2-3
Density: 4.67 g/cm³
Colors: Yellow White Colorless
Streak: White
Luster: Adamantine
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Acicular Crystals, Fibrous, Encrustations
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Volcanic Fumaroles
Typical price: $50-500 depending on specimen quality

Where rockhounds find pseudocotunnite

Classic worldwide localities

Vesuvius, Italy
Tolbachik volcano, Russia

Field-hunting tip

Look in volcanic fumaroles country — that is the host setting where pseudocotunnite typically forms. If you start seeing cotunnite, galena, halite in float, you are in the right ground. Field specimens usually show a acicular crystals, fibrous, encrustations habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify pseudocotunnite?+

Mohs hardness is 2-3. It typically shows a adamantine luster. The streak is white. Common colors include yellow, white, colorless.

Where is pseudocotunnite found?+

Notable localities include Vesuvius, Italy; Tolbachik volcano, Russia.

How much is pseudocotunnite worth?+

Typical asking prices fall in the range of $50-500 depending on specimen quality. Quality, size, and provenance can move individual specimens well outside that range.

Is pseudocotunnite safe to handle?+

It contains toxic constituents. Contains lead, a toxic heavy metal. Wash hands thoroughly after handling and avoid ingestion or inhalation of dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like pseudocotunnite?+

Pseudocotunnite is most often confused with Cotunnite, Matlockite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with pseudocotunnite?+

Pseudocotunnite commonly co-occurs with Cotunnite, Galena, Halite, Sylvite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does pseudocotunnite form in?+

Pseudocotunnite typically forms in volcanic fumaroles. Working float back to the host body is the standard way to chase a fresh occurrence.

What is pseudocotunnite used for?+

Pseudocotunnite is used in collector.

Find pseudocotunnite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.