What is Löllingite?
Löllingite is a dense iron arsenide with metallic grey colour, important in ore mineralogy and valued by collectors for its heavy, steel-like appearance.
Mineralogy and crystal structure
Reference formula: FeAs2. Löllingite has an orthorhombic marcasite-type structure and forms compositional relationships with arsenopyrite and other iron-nickel-cobalt arsenides. Its arsenic content means that visual inspection should be supplemented by analytical identification. Löllingite is classified with sulfides and has a orthorhombic crystal system. Typical hardness is 5–5.5 on the Mohs scale and specific gravity is approximately 7.1–7.5.
Colour, lustre and habit
Typical colours include tin-white, silver-grey, grey-black. The usual prismatic, granular, massive habit and metallic, sub-metallic lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Löllingite forms in or is associated with hydrothermal ore veins, metamorphic deposits and arsenic-rich skarns or pegmatites. Important documented localities include Austria, the Czech Republic, Germany, Sweden, Canada and the United States.
A heavy metallic mineral with ore-science appeal
Löllingite is compelling for collectors who enjoy the material presence of ore minerals. Its pale metallic surfaces and high density invite comparison with arsenopyrite, while the documented locality reveals the chemistry of an arsenic-rich deposit.
Collecting and care
Arsenic-bearing ore: keep sealed from dust, avoid cutting or grinding, wash hands after handling and never use as a decorative or jewellery material.
