Willyamite is a very rare member of the cobaltite group, found primarily in hydrothermal ore deposits. It typically appears as massive or granular metallic aggregates that are difficult to distinguish from other sulfosalt minerals without chemical analysis.

Hardness

5-5.5

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrareCobaltite Group family

Willyamite

Hardness: 5-5.5
Luster: Metallic
Streak: Black
Transparency: Opaque

Is this willyamite?

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 willyamite with a known reference. Willyamite sits at Mohs 5-5.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Willyamite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Willyamite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: white, gray.
5
Look at form & habit
Crystal system: cubic. Typical habit: massive to granular.

Often confused with

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

mineral

Cobaltite

Mohs 5.5

How to tell apart: Streak differs — Willyamite leaves black, Cobaltite leaves greyish-black.

How to tell apart: Streak differs — Willyamite leaves black, Gersdorffite leaves grayish-black.

Often found alongside willyamite

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

All properties

Chemical formula: (Co,Ni)SbS
Mohs hardness: 5-5.5
Density: 6.7 g/cm³
Colors: White Gray
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Cubic
Crystal habit: Massive to Granular
Cleavage: None
Rarity: Rare
Uses: Collector, Scientific Research
Host rock: Hydrothermal Veins
Typical price: $50-300 per specimen depending on size and rarity

Where rockhounds find willyamite

Classic worldwide localities

Broken Hill, New South Wales, Australia
Bou Azzer, Morocco

Field-hunting tip

Look in hydrothermal veins country — that is the host setting where willyamite typically forms. If you start seeing cobaltite, gersdorffite, safflorite in float, you are in the right ground. Field specimens usually show a massive to granular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify willyamite?+

Mohs hardness is 5-5.5. It typically shows a metallic luster. The streak is black. Common colors include white, gray.

Where is willyamite found?+

Notable localities include Broken Hill, New South Wales, Australia; Bou Azzer, Morocco.

How much is willyamite worth?+

Typical asking prices fall in the range of $50-300 per specimen depending on size and rarity. Quality, size, and provenance can move individual specimens well outside that range.

Is willyamite safe to handle?+

It contains toxic constituents. Contains cobalt, nickel, antimony, and sulfur; handle with care to avoid inhalation of dust or ingestion. Wash hands thoroughly after handling. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like willyamite?+

Willyamite is most often confused with Cobaltite, Gersdorffite, Ullmannite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with willyamite?+

Willyamite commonly co-occurs with Cobaltite, Gersdorffite, Safflorite, Breithauptite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does willyamite form in?+

Willyamite typically forms in hydrothermal veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is willyamite used for?+

Willyamite is used in collector, scientific research.

Find willyamite on the map

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