Radiating cluster of cavernous crystals of ferrisanidine on cassiterite (bright phase). SEM (BSE mode) image. The image is published in an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( https://creativecommons.org/licenses/by/4.0/ ). — Photo: Shchipalkina, Nadezhda V. and Pekov, Igor V. and Britvin, Sergey N. and Koshlyakova, Natalia N. and Vigasina, Marina F. and Sidorov, Evgeny G. · CC BY 4.0
Ferrisanidine
Ferrisanidine is an IMA-recognized mineral species in the silicate class, with the chemical formula K(Fe³⁺Si₃O₈).
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Feldspar structural group.
Key properties: specific gravity 2.722; White streak; Vitreous luster.
IMA symbol Fsa, IMA status: approved, named in 2019.
Forms as a sublimate around an active volcanic fumarole (Russia). In lamproite (USA).
It is found associated with Aegirine, cassiterite, hematite, sylvite, halite, johillerite, arsmirandite, axelite, aphthitalite, badalovite, litidionite, tridymite, polyarsite, evseevite.
The prefix indicates an analogue of sanidine with essential Fe3+ > Al.