Linnaeusit

Linnaeite is a rare mineral composed of cobalt, nickel, and sulfur, with the chemical formula (Co,Ni)3S4. It is a member of the thiospinel group and is isostructural with the mineral linnaeite. Linnaeite typically occurs as metallic, grayish-white to pale brass-yellow crystals. It is often found in hydrothermal veins and associated with other cobalt and nickel minerals.

The mineral was first described in 1845 from a deposit in the Skutterud Mine, Modum, Norway. It was named in honor of the Swedish botanist Carl Linnaeus. Linnaeite is known for its distinctive magnetic properties, being ferromagnetic at room temperature. It is relatively soft, with a Mohs hardness of 4.5 to 5.5, and has a specific gravity of around 4.8 to 5.0.

While not a primary ore of cobalt or nickel, linnaeite can be a minor source of these metals. Its rarity and occurrence in specific geological environments make it of interest to mineral collectors and geologists studying ore deposits. It is often found alongside minerals such as chalcopyrite, pyrite, and cobaltite. The occurrence of linnaeite is often indicative of low-sulfidation epithermal or mesothermal environments.