(d) The same image under polarized and analysed light. One of the sections has an hourglass zoning and something resembling polysynthetic twins with thin plates. — Photo: Antonia Cepedal, Mercedes Fuertes-Fuente, Agustín Martin-Izard · CC BY 4.0
Silesiaite
Silesiaite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₂Fe³⁺Sn(Si₂O₇)(Si₂O₆OH).
It crystallizes in the triclinic crystal system (space group C1). It is a member of the Kristiansenite structural group.
Key properties: optically biaxial.
IMA symbol Ssa, IMA status: approved, named in 2017.
Found in granitic pegmatite (Poland); in calcic Cu-Au skarn (Spain).
It is found associated with Andradite (Adr96-100), clinopyroxene (Hd30-47), actinolite, apophyllite-(KOH), babingtonite, hydroandradite, quartz, calcite, chalcopyrite (Spain).
The name refers to the region of Poland where the studied material was collected.