What is Caesiumpharmacosiderite?
Caesiumpharmacosiderite is a rare caesium-bearing iron arsenate hydrate, related to pharmacosiderite and found in oxidised arsenic-rich mineral assemblages.
Mineralogy and structure
The reference formula is CsFe4[(AsO4)3(OH)4]·4H2O. Caesiumpharmacosiderite belongs to the arsenates and crystallises in the cubic system. The cubic framework hosts caesium and hydrated iron-arsenate groups. The name identifies a specific compositional member, not a generic synonym for pharmacosiderite. Handle all arsenate specimens as display material and avoid dust.
Colour and appearance
Typical colours include yellow, greenish yellow and brownish yellow. For small or complex mineral species, crystal size, transparency, lustre and matrix association are often more diagnostic than colour alone.
Formation and localities
Caesiumpharmacosiderite forms in or is associated with oxidised arsenic-bearing hydrothermal deposits. Important documented localities include Chile and other rare arsenate localities. A precise mine or geological setting is preferable to a broad country label when it is known.
Collecting and care
Caesiumpharmacosiderite is best treated as a labelled reference or collector specimen. Protect fragile crystals from impact and humidity changes. Arsenic-, cadmium-, lead-, thorium- and selenium-bearing minerals should not be cut, ground or used in jewellery; wash hands after handling and keep them away from food and children.
