What is Mimetite?
Mimetite gives oxidised lead deposits a warm colour range from lemon yellow to orange. Sharp barrel-shaped crystals are particularly attractive when they remain attached to galena or a contrasting iron-rich matrix.
Mineralogy and crystal structure
Reference formula: Pb5(AsO4)3Cl. Mimetite is a hexagonal lead arsenate chloride with an apatite-like framework. It forms a series with pyromorphite and vanadinite, so colour alone cannot separate these related secondary lead minerals. Mimetite is classified with arsenates and has a hexagonal crystal system. Typical hardness is 3.5–4 on the Mohs scale and specific gravity is approximately 7.1–7.3.
Colour, lustre and habit
Typical colours include yellow, orange, brown, green. The usual hexagonal, barrel-shaped, botryoidal habit and resinous, vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Mimetite forms in or is associated with oxidised zones of lead deposits where arsenate-rich fluids react with galena and other primary ores. Important documented localities include Mexico, Namibia, Germany, France, the United Kingdom and Australia.
Honey-yellow barrels from a weathered lead vein
Mimetite gives oxidised lead deposits a warm colour range from lemon yellow to orange. Sharp barrel-shaped crystals are particularly attractive when they remain attached to galena or a contrasting iron-rich matrix.
Collecting and care
Lead- and arsenic-bearing: keep enclosed, avoid dust and acids, do not cut or grind, and wash hands after handling.
