Ullmannite is a nickel antimony sulfide that typically appears as cubic or pyritohedral metallic crystals. It is primarily found in hydrothermal veins associated with other sulfide minerals and is valued by collectors for its sharp crystal habits and distinct metallic luster.

Hardness

5-5.5

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineraluncommonCobaltite Group family

Ullmannite

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

Is this ullmannite?

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 ullmannite with a known reference. Ullmannite 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. Ullmannite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Ullmannite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: silver-white, steel-gray.
5
Look at form & habit
Crystal system: cubic. Typical habit: cubic crystals, massive, granular.

Often confused with

Ullmannite 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 — Ullmannite leaves black, Cobaltite leaves greyish-black.

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

Often found alongside ullmannite

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

All properties

Chemical formula: NiSbS
Mohs hardness: 5-5.5
Density: 6.6-6.7 g/cm³
Colors: Silver-white Steel-gray
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Cubic
Crystal habit: Cubic Crystals, Massive, Granular
Cleavage: Perfect Cubic
Rarity: Uncommon
Uses: Collector, Ore
Host rock: Hydrothermal Veins
Typical price: $20-150 for small specimens

Where rockhounds find ullmannite

Classic worldwide localities

Siegen, Germany
Broken Hill, Australia
Cobalt, Ontario, Canada
Pribram, Czech Republic

Field-hunting tip

Look in hydrothermal veins country — that is the host setting where ullmannite typically forms. If you start seeing galena, siderite, chalcopyrite in float, you are in the right ground. Field specimens usually show a cubic crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify ullmannite?+

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

Where is ullmannite found?+

Notable localities include Siegen, Germany; Broken Hill, Australia; Cobalt, Ontario, Canada; Pribram, Czech Republic.

How much is ullmannite worth?+

Typical asking prices fall in the range of $20-150 for small specimens. Quality, size, and provenance can move individual specimens well outside that range.

Is ullmannite safe to handle?+

It contains toxic constituents. Ullmannite contains nickel, antimony, and sulfur. Avoid inhaling dust during handling or lapidary work, and wash hands thoroughly after contact. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like ullmannite?+

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

What minerals are found with ullmannite?+

Ullmannite commonly co-occurs with Galena, Siderite, Chalcopyrite, Sphalerite, Niccolite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does ullmannite form in?+

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

What is ullmannite used for?+

Ullmannite is used in collector, ore.

Find ullmannite on the map

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