What is Cafarsite?
Cafarsite is a rare complex calcium titanium iron arsenite-arsenate mineral from alpine fissures and alkaline mineral assemblages.
Mineralogy and structure
The reference formula is (Ca,Na,□)19Ti8Fe4+4Fe2+4(AsO3)28F. Cafarsite belongs to the arsenates and crystallises in the cubic system. Its cubic structure accommodates vacancies and several iron valence states, which explains the complex formula. Cafarsite is a specialist collector mineral often associated with quartz, magnetite, hematite and arsenic minerals.
Colour and appearance
Typical colours include black, dark brown and reddish brown. For small or complex mineral species, crystal size, transparency, lustre and matrix association are often more diagnostic than colour alone.
Formation and localities
Cafarsite forms in or is associated with highly evolved alpine fissures and arsenic-rich alkaline environments. Important documented localities include the Binn Valley in Switzerland and Monte Cervandone in Italy. A precise mine or geological setting is preferable to a broad country label when it is known.
Collecting and care
Cafarsite 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.
