Ullmannite is a nickel

Nickel

Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...

 antimony

Antimony

Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...

 sulfide

Sulfide

A sulfide is an anion of sulfur in its lowest oxidation state of 2-. Sulfide is also a slightly archaic term for thioethers, a common type of organosulfur compound that are well known for their bad odors.- Properties :...

 mineral

Mineral

A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...

 with formula: NiSbS. Considerable substitution occurs with cobalt

Cobalt

Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....

 and iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 in the nickel site along with bismuth

Bismuth

Bismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...

 and arsenic

Arsenic

Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...

 in the antimony site. A solid solution

Solid solution

A solid solution is a solid-state solution of one or more solutes in a solvent. Such a mixture is considered a solution rather than a compound when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the mixture remains in a single homogeneous phase...

 series exists with the high cobalt willyamite.

Physical properties

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

Specific gravity

Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...

 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 enantiomorphic twinning along [110].

Occurrence

It is a member of the cobaltite

Cobaltite

Cobaltite is a sulfosalt mineral composed of cobalt, arsenic and sulfur, CoAsS. It contains up to 10 percent iron and variable amounts of nickel. Structurally it resembles pyrite with one of the sulfur atoms replaced by an arsenic atom....

 group and forms a series with willyamite ((Co,Ni)SbS). It occurs with nickeline, gersdorffite

Gersdorffite

Gersdorffite is a nickel arsenic sulfide mineral with formula NiAsS. It crystallizes in the isometric system showing diploidal symmetry. It occurs as euhedral to massive opaque, metallic grey-black to silver white forms. Gersdorffite belongs to a solid solution series with cobaltite, CoAsS....

, pentlandite

Pentlandite

Pentlandite is an iron-nickel sulfide, 9S8. Pentlandite usually has a Ni:Fe ratio of close to 1:1. It also contains minor cobalt.Pentlandite forms isometric crystals, but is normally found in massive granular aggregates. It is brittle with a hardness of 3.5 - 4 and specific gravity of 4.6 - 5.0 and...

, chalcopyrite

Chalcopyrite

Chalcopyrite is a copper iron sulfide mineral that crystallizes in the tetragonal system. It has the chemical composition CuFeS2. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green tinged black.On exposure to air, chalcopyrite...

, pyrrhotite

Pyrrhotite

Pyrrhotite is an unusual iron sulfide mineral with a variable iron content: FeS . The FeS endmember is known as troilite. Pyrrhotite is also called magnetic pyrite because the color is similar to pyrite and it is weakly magnetic...

, galena

Galena

Galena is the natural mineral form of lead sulfide. It is the most important lead ore mineral.Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms...

, tetrahedrite

Tetrahedrite

Tetrahedrite is a copper antimony sulfosalt mineral with formula: 12Sb4S13. It is the antimony endmember of the continuous solid solution series with arsenic bearing tennantite. Pure endmembers of the series are seldom if ever seen in nature. Of the two, the antimony rich phase is more common...

 and dyscrasite

Dyscrasite

The silver antimonide mineral dyscrasite has the chemical formula Ag3Sb. It is an opaque, silver white, metallic mineral which crystallizes in the orthorhombic crystal system. It forms pyramidal crystals up to 5 cm and can also form cylindrical and prismatic crystals.-Crystallography and...

 in hydrothermal deposits.

Principal localities are in Germany

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

, it is also found in Austria

Austria

Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...

, Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

, and Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

.

It was first described in 1843 for an occurrence in the Storch und Schöneberg Mine, North Rhine-Westphalia

North Rhine-Westphalia

North Rhine-Westphalia is the most populous state of Germany, with four of the country's ten largest cities. The state was formed in 1946 as a merger of the northern Rhineland and Westphalia, both formerly part of Prussia. Its capital is Düsseldorf. The state is currently run by a coalition of the...

, Germany

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

.

Specimens of ullmannite were found at Sarrabus, Sardinia

Sardinia

Sardinia is the second-largest island in the Mediterranean Sea . It is an autonomous region of Italy, and the nearest land masses are the French island of Corsica, the Italian Peninsula, Sicily, Tunisia and the Spanish Balearic Islands.The name Sardinia is from the pre-Roman noun *sard[],...

, Italy in 1887. The crystals of the specimens from Sarrabus were described as hemihedral

Hemipolyhedron

In geometry, a hemipolyhedron is a uniform star polyhedron some of whose faces pass through its center. These "hemi" faces lie parallel to the faces of some other symmetrical polyhedron, and their count is half the number of faces of that other polyhedron - hence the "hemi" prefix.The prefix "hemi"...

 with parallel faces, whereas specimens from Lölling in present-day Austria were hemihedral with inclined faces.

Origin of name

Ullmannite was named for German

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 chemist

Chemist

A chemist is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties such as density and acidity. Chemists carefully describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms...

 and mineralogist, Johann Christoph Ullmann (1771–1821), one of the fathers of systematic mineralogy. Ullmann established a mineral collection (now the basis for the internationally renowned Museum of Mineralogy in Marburghttp://www.uni-marburg.de/fb19/minmus)and authored Ein Systematisch-Tabellarische Übersicht der Mineralogisch einfachen Fossilien, one of the first attempts to provide a structured organization to the observed minerals of the day.