Glaucodot is a 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....

 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...

 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...

 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 with formula: (Co,Fe)AsS. The cobalt:iron(II) ratio is typically 3:1 with minor 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...

 substituting. It forms a series with arsenopyrite (FeAsS). It is an opaque grey to tin-white typically found as massive forms without external crystal form. It crystallizes in the orthorhombic system. The locality at Håkansboda, Sweden

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

 has rare twinned

Crystal twinning

Crystal twinning occurs when two separate crystals share some of the same crystal lattice points in a symmetrical manner. The result is an intergrowth of two separate crystals in a variety of specific configurations. A twin boundary or composition surface separates the two crystals....

 dipyramidal crystals (see photo). It is brittle with a Mohs hardness of 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 5.95. It occurs in high temperature hydrothermal deposits with 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...

 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...

. Glaucodot is classed as a sulfide in the arsenopyrite

Arsenopyrite

Arsenopyrite is an iron arsenic sulfide . It is a hard metallic, opaque, steel grey to silver white mineral with a relatively high specific gravity of 6.1. When dissolved in nitric acid, it releases elemental sulfur. When arsenopyrite is heated, it becomes magnetic and gives off toxic fumes...

 löllingite

Lollingite

Loellingite, also spelled löllingite, is an iron arsenide mineral with formula FeAs2. It is often found associated with arsenopyrite from which it is hard to distinguish. Cobalt, nickel and sulfur substitute in the structure. The orthorhombic lollingite group includes the nickel iron arsenide...

 group.

Glaucodot was first described in 1849 in Huasco, Valparaíso Province

Valparaíso Province

Valparaíso Province is one of eight provinces of the central Chilean region of Valparaíso . Its capital is the coastal city of Valparaíso Valparaíso Province is one of eight provinces of the central Chilean region of Valparaíso (V). Its capital is the coastal city of Valparaíso Valparaíso...

, Chile

Chile

Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...

. Its name originates from the Greek γλανκός ("blue") in reference to its use in the dark blue glass called smalt

Smalt

Smalt is powdered glass, colored to a deep powder blue hue using cobalt ions derived from cobalt oxide . Smalt is used as a pigment in painting, and for surface decoration of other types of glass and ceramics, and other media...

.