Crerarite is an extremely rare platinum-group mineral found as tiny inclusions or irregular aggregates within massive sulfides. It is primarily identified through electron microprobe analysis given its microscopic habit and similarity to other opaque metallic minerals.

Hardness

~3.5

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrare

Crerarite

Hardness: ~3.5
Luster: Metallic
Streak: Black
Transparency: Opaque

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Is this crerarite?

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 crerarite with a known reference. Crerarite sits at Mohs ~3.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: black.
3
Read the luster
Hold the specimen under a strong light. Luster: metallic.
4
Match the color range
Compare against the expected color range: black.
5
Look at form & habit
Crystal system: cubic. Typical habit: granular.

Often confused with

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

mineral

Sperrylite

Mohs 6-7

How to tell apart: Sperrylite is the harder of the two (Mohs 6-7 vs. ~3.5).

How to tell apart: Crerarite is noticeably harder (Mohs ~3.5 vs. 2.5-2.75); streak differs, so Crerarite leaves black, Galena leaves lead-gray.

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Often found alongside crerarite

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

All properties

Chemical formula: (Pt,Pb)Bi₃(S,Se)₄
Mohs hardness: ~3.5
Density: 7.75 g/cm³
Colors: Black
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Cubic
Crystal habit: Granular
Cleavage: Perfect on {001}
Rarity: Rare
Uses: Collector
Host rock: In an amphibolite boulder, perhaps glacially transported, containing sulfides

Where rockhounds find crerarite

Classic worldwide localities

Lake Sheen, Belleterre, Guillet township, Abitibi-Temiscaminque region, Quebec, Canada (type locality)

Field-hunting tip

Where it forms: In an amphibolite boulder, perhaps glacially transported, containing sulfides. If you start seeing chalcopyrite, pentlandite, pyrrhotite in float, you are in the right ground. Typical habit: granular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify crerarite?+

Mohs hardness is ~3.5. Luster: metallic. The streak is black. Common colors include black.

Where is crerarite found?+

Notable localities include Lake Sheen, Belleterre, Guillet township, Abitibi-Temiscaminque region, Quebec, Canada (type locality).

Is crerarite safe to handle?+

Crerarite contains lead and selenium. Contains lead (Pb); wash hands thoroughly after handling and avoid ingestion or inhalation of dust.

What rocks look like crerarite?+

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

What minerals are found with crerarite?+

Crerarite commonly co-occurs with Chalcopyrite, Pentlandite, Pyrrhotite, Sphalerite, Galena, Michenerite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does crerarite form in?+

Where it forms: In an amphibolite boulder, perhaps glacially transported, containing sulfides. Working float back to the host body is the standard way to chase a fresh occurrence.

What is crerarite used for?+

Crerarite is used in collector.

Find crerarite on the map

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