Challacolloite is a very rare potassium lead chloride mineral discovered at its namesake locality in the Challacollo mine of Chile. It typically forms as thin crusts or coatings in volcanic fumarole environments and is often associated with other halide minerals. Due to its extreme rarity and tendency to form small, fragile aggregates, it is primarily sought after by advanced systematic mineral collectors.

Hardness

2-3

Mohs

Luster

Adamantine to greasy (on exposure to air)

Streak

White

Transparency

Translucent

mineralrare

Challacolloite

Hardness: 2-3
Luster: Adamantine to greasy (on exposure to air)
Streak: White
Transparency: Translucent

Is this challacolloite?

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 challacolloite with a known reference. Challacolloite 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. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: adamantine to greasy (on exposure to air).
4
Match the color range
Compare against the expected color range: white, colorless.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: aggregates.

Often confused with

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

Often found alongside challacolloite

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

All properties

Chemical formula: KPb₂Cl₅
Mohs hardness: 2-3
Density: 4.77 g/cm³
Colors: White Colorless
Streak: White
Luster: Adamantine to greasy (on exposure to air)
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Aggregates
Rarity: Rare
Uses: Collector
Host rock: A hydrothermal mineral in an epithermal vein-type silver deposit (Chile)

Where rockhounds find challacolloite

Classic worldwide localities

Challacollo silver mine, south east of Iquique, Atacama desert, northern Chile
Vesuvius, Naples, Campania, and La Fossa crater, Vulcano, Aeolian Archipelago, Sicily, Italy

Field-hunting tip

Where it forms: A hydrothermal mineral in an epithermal vein-type silver deposit (Chile). If you start seeing cotunnite, boleite, pseudoboleite in float, you are in the right ground. Typical habit: aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify challacolloite?+

Mohs hardness is 2-3. Luster: adamantine to greasy (on exposure to air). The streak is white. Common colors include white, colorless.

Where is challacolloite found?+

Notable localities include Challacollo silver mine, south east of Iquique, Atacama desert, northern Chile; Vesuvius, Naples, Campania, and La Fossa crater, Vulcano, Aeolian Archipelago, Sicily, Italy.

Is challacolloite safe to handle?+

Challacolloite contains lead. Contains lead, which is toxic if ingested or inhaled as dust; wash hands thoroughly after handling and keep away from food.

What rocks look like challacolloite?+

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

What minerals are found with challacolloite?+

Challacolloite commonly co-occurs with Cotunnite, Boleite, Pseudoboleite, Hemimorphite, Caracoite, Anglesite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does challacolloite form in?+

Where it forms: A hydrothermal mineral in an epithermal vein-type silver deposit (Chile). Working float back to the host body is the standard way to chase a fresh occurrence.

What is challacolloite used for?+

Challacolloite is used in collector.

Find challacolloite on the map

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