Linnaeite is a mineral that has the chemical formula of Co3S4 and belongs to the pyrite group. Synonyms for Linnaeite include cobalt pyrites, cobalt bloom, cobaltite, cobalt nickel pyrites, copper smaltite, and more. These minerals contain high concentrations of cobalt, which makes them important sources for cobalt extraction. Linnaeite is typically found in hydrothermal veins, and can also be found in some sedimentary rocks and geothermal deposits. These minerals have various colors, ranging from gray to silver, and have a metallic luster. They have been used in various applications, such as in the production of batteries, magnetic materials, and pigments.