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

Grayish black

Transparency

Opaque

mineraluncommonCobaltite Group family

Ullmannite

Hardness: 5-5.5
Luster: Metallic
Streak: Grayish 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. Streak: grayish 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: silver white, steel gray, tin white.
5
Look at form & habit
Crystal system: cubic. Typical habit: massive.

Often confused with

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

How to tell apart: Streak differs, so Ullmannite leaves grayish black, Arsenopyrite leaves black.

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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: 6.65 g/cm³
Colors: Silver white Steel gray Tin white
Streak: Grayish black
Luster: Metallic
Transparency: Opaque
Crystal system: Cubic
Crystal habit: Massive
Cleavage: Perfect on {001}
Rarity: Uncommon
Uses: Collector, Ore
Host rock: With nickel minerals in hydrothermal veins

Where rockhounds find ullmannite

Classic worldwide localities

Friedrich mine, near Wissen, Germany
Petersbach mine, near Eichelhardt, Germany
Gosenbach, Germany
Salchendorf, Germany
Ramsbeck, Germany
Harz Mountains, from Neudorf, Germany

Field-hunting tip

Where it forms: With nickel minerals in hydrothermal veins. If you start seeing nickeline, gersdorffite, pentlandite in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify ullmannite?+

Mohs hardness is 5-5.5. Luster: metallic. The streak is grayish black. Common colors include silver white, steel gray, tin white.

Where is ullmannite found?+

Notable localities include Friedrich mine, near Wissen, Germany; Petersbach mine, near Eichelhardt, Germany; Gosenbach, Germany; Salchendorf, Germany; Ramsbeck, Germany.

Is ullmannite safe to handle?+

Ullmannite contains antimony and nickel. Ullmannite contains nickel, antimony, and sulfur. Avoid inhaling dust during handling or lapidary work, and wash hands thoroughly after contact.

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 Nickeline, Gersdorffite, Pentlandite, Chalcopyrite, Pyrrhotite, Galena. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does ullmannite form in?+

Where it forms: With nickel minerals 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.