What is Naumannite?
Naumannite is a dense silver selenide of low-temperature hydrothermal veins, important as a silver ore and a specialist sulfosalt-suite mineral.
Mineralogy and crystal structure
Reference formula: Ag2Se. Naumannite is the low-temperature orthorhombic form of silver selenide and can show polymorphic behaviour. Its silver and selenium content makes assay, locality and safe handling more important than surface appearance. Naumannite is classified with sulfides and has a orthorhombic crystal system. Typical hardness is 2.5–3 on the Mohs scale and specific gravity is approximately 7.2–7.3.
Colour, lustre and habit
Typical colours include silver-grey, lead-grey, black. The usual granular, massive, crystalline habit and metallic lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Naumannite forms in or is associated with selenium-rich low-temperature hydrothermal veins and silver-polymetallic ore deposits. Important documented localities include Mexico, Germany, the Czech Republic, Peru, Bolivia and Canada.
Heavy grey metal in a selenium-rich silver vein
Naumannite is a specialist ore mineral whose subdued surface hides a dense silver-selenium structure. It is most informative in a documented polymetallic association.
Collecting and care
Keep enclosed, avoid dust and cutting, and wash hands after handling.
