What is Köttigite?
Köttigite is a hydrated zinc arsenate known for soft pink fibrous aggregates and its place in the oxidised zones of zinc-arsenic deposits.
Mineralogy and crystal structure
Reference formula: Zn3(AsO4)2·8H2O. Köttigite has a monoclinic hydrated arsenate structure and is part of the köttigite-parasymplesite solid-solution system. Its colour and dehydration behaviour can vary with composition and storage conditions. Köttigite is classified with phosphates and has a monoclinic crystal system. Typical hardness is 2.5–3 on the Mohs scale and specific gravity is approximately 3.1–3.3.
Colour, lustre and habit
Typical colours include pink, rose, white, colourless. The usual fibrous, radiating, crusty habit and vitreous, pearly, silky lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Köttigite forms in or is associated with supergene oxidation zones above zinc-bearing hydrothermal ores. Important documented localities include Germany, Mexico, Namibia, the United States and Europe.
Soft rose colour with a serious mineralogical story
Köttigite is a memorable micro-mineral because its delicate rose fibres contrast with the chemistry of a weathered ore deposit. It is best sold and displayed as a documented collector specimen, never as a casual decorative stone.
Collecting and care
Arsenate-bearing and soft: keep sealed from dust, avoid cutting or grinding, wash hands after handling and keep away from food.
