What is Wurtzite?
Wurtzite is the hexagonal polymorph of zinc sulfide, found in hydrothermal ore deposits and valued for its crystal form, chemistry and relation to sphalerite.
Mineralogy and structure
Reference formula: ZnS. Wurtzite has the hexagonal ZnS structure and is the polymorph counterpart of cubic sphalerite. COD 1011195 provides an exact structural reference; intergrowths are common. Wurtzite is classified with sulfides and has hexagonal crystal symmetry. Typical hardness is 3.5–4 on the Mohs scale and specific gravity is approximately 3.9–4.1.
Colour, lustre and habit
Typical colours include brown, black, yellow-brown, red-brown, grey. The usual prismatic, granular, massive habit and resinous, sub-metallic, adamantine lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Wurtzite forms in or is associated with hydrothermal zinc deposits, volcanic fumaroles, meteorites and high-temperature ore assemblages. Important documented localities include Bolivia, Peru, Mexico, the United States, Romania, Germany and Russia.
The hexagonal face of zinc sulfide
Wurtzite is a compelling companion to sphalerite: the same chemistry produces a different structure, while dark lustre and crystal habit tell the geological story.
Collecting and care
Protect from impact and acids, avoid dust-producing work and preserve the ore association; do not identify a specimen by colour alone.
