What is Legrandite?
Legrandite is a rare bright yellow zinc arsenate, famous for sharp crystals from the oxidised zones of zinc deposits.
Mineralogy and crystal structure
Reference formula: Zn2AsO4OH·H2O. Legrandite is a monoclinic hydrated zinc arsenate and is related to adamite and paradamite in the oxidised zinc-ore environment. The combination of colour, crystal form and locality is more diagnostic than yellow colour alone. Legrandite is classified with arsenates and has a monoclinic crystal system. Typical hardness is 4–4.5 on the Mohs scale and specific gravity is approximately 4.2–4.4.
Colour, lustre and habit
Typical colours include yellow, golden yellow, orange, greenish yellow. The usual prismatic, radiating, botryoidal habit and vitreous, pearly lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Legrandite forms in or is associated with supergene oxidation zones of zinc- and arsenic-bearing hydrothermal ores. Important documented localities include Mexico, Namibia, Germany, the United States and Australia.
Golden yellow in a world-class collector mineral
Legrandite is a classic example of why rarity and crystal quality can outweigh size. Its saturated yellow colour and radiating or prismatic forms create an immediate focal point, especially when the specimen retains the Mexican or Namibian locality context.
Collecting and care
Arsenate-bearing and moderately soft: keep enclosed from dust, avoid acids and grinding, wash hands after handling and keep away from food.
