What is Zykaite?
Zykaite is a very soft hydrated ferric arsenate sulfate from mine oxidation zones, usually forming pale earthy or fibrous crusts rather than showy crystals.
Mineralogy and structure
Reference formula: Fe4(AsO4)3(SO4)(OH)·15H2O. Zykaite is orthorhombic with the ideal formula Fe4(AsO4)3(SO4)(OH)·15H2O. Its high water content explains its fragility; no public CIF was selected for this batch, so the Guide does not invent a lattice image. Zykaite is classified with arsenates and has orthorhombic crystal symmetry. Typical hardness is 2–2 on the Mohs scale and specific gravity is approximately 2.5–2.7.
Colour, lustre and habit
Typical colours include greyish white, light yellow, light green. The usual fibrous, crusty, massive habit and dull, pearly lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Zykaite forms in or is associated with secondary oxidation of arsenic- and sulfide-bearing ores in mine workings. Important documented localities include Czechia, Poland, Germany and other European arsenic mining districts.
A fragile mine crust with a clear chemical signature
Zykaite is not a large-crystal showpiece; its appeal is authenticity. A documented crust preserves the chemistry of a mine oxidation zone and belongs in a careful specialist collection.
Collecting and care
Arsenic-bearing, hydrated and extremely soft: keep sealed and dry, avoid dust, heat, water and abrasion, and handle only as a protected reference specimen.
