Rakosien

Rakosien is a rare metallic mineral classed among sulfide minerals. It is characterized by a dense, steel-gray to black appearance and a metallic luster. The composition is dominated by iron and nickel with sulfur as the primary anion, and minor amounts of copper and cobalt have been reported in some samples. The mineral typically occurs as prismatic to tabular crystals and can form in hydrothermal ore veins.

Crystallographic studies associate rakosien with a monoclinic system, though twinning and solid-solution with related sulfides are common. It has a Mohs hardness of about 5–6 and an estimated specific gravity of 7.6–8.2 g/cm3. It is not magnetic or only weakly magnetic depending on impurities.

Rakosien was first described in 1992 by geologist L. Rako in the fictional Rakos Massif in the eastern tectonic belt. It occurs mainly in ultramafic to mafic intrusions and hydrothermal veins, often alongside pentlandite, pyrrhotite, and chalcopyrite. The formation is associated with nickel-rich sulfide deposits and late-stage hydrothermal fluids.

Economic significance is limited by rarity; rakosien is considered a potential nickel ore but has not been mined on a commercial scale. It is of interest to mineralogists for the study of sulfide solid solutions and alloying behavior.