How do I identify Ullmannite?

Ullmannite can be identified by its hardness of 5 - 5.5 on the Mohs scale, Tin-white color. Look for these key characteristics when examining specimens.

What color is Ullmannite?

Ullmannite typically appears in Tin-white, steel grey. Color can vary depending on impurities and formation conditions.

How hard is Ullmannite?

Ullmannite has a hardness of 5 - 5.5 on the Mohs scale. This gives it moderate hardness.

Ullmannite

A variety of Cobaltite Group

What is Ullmannite?

Ullmannite is a nickel antimony sulfide mineral with formula: NiSbS. Considerable substitution occurs with cobalt and iron in the nickel site along with bismuth and arsenic in the antimony site. A solid solution series exists with the high cobalt willyamite.

Ullmannite Market Value Calculator

Estimate the market value of Ullmannite using size, quality, and finish. This preview calculator is for quick context and is not a formal appraisal.

Ullmannite Localities Map

See where Ullmannite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.

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North ZoneCentral RidgeSouth Basin

Key Characteristics

Characteristics of Ullmannite

Ullmannite is steel-gray to tin white in color with a metallic luster, has a Mohs hardness of 5 to 5.5 and a specific gravity of 6.65. Initially thought to be of two species, tetrahedral and cubic, it was later confirmed that both samples conformed to the 23 point group of the isometric crystal class and typically exhibits cubic, octahedral, or pyritohedral forms although euhedral crystals are rare. Variance in its chemical composition has been shown to be responsible for loss of symmetry and variations in striation patterns. Ullmannite crystals are usually less than 2 mm, however larger have been identified in especially antimony rich environments. Ullmannite commonly displays interpenetration twins as well as enantiomorphic twinning along [110].

Formation of Ullmannite

It is a member of the cobaltite group and forms a series with willyamite ((Co,Ni)SbS). It occurs with nickeline, gersdorffite, pentlandite, chalcopyrite, pyrrhotite, galena, tetrahedrite and dyscrasite in hydrothermal deposits. Principal localities are in Germany, it is also found in Austria, Australia, France, England, and Wales. It was first described in 1843 for an occurrence in the Storch und Schöneberg Mine, North Rhine-Westphalia, Germany. Specimens of ullmannite were found at Sarrabus, Sardinia, Italy in 1887. The crystals of the specimens from Sarrabus were described as hemihedral with parallel faces, whereas specimens from Lölling in present-day Austria were hemihedral with inclined faces.