Chiolite
A tetragonal sodium-aluminium fluoride whose name comes from the Greek words for 'snow' and 'stone'.
Intro adapted from Wikipedia (CC BY-SA).
Chiolite is an IMA-recognized mineral species in the halide class, with the chemical formula Na₅Al₃F₁₄.
It crystallizes in the tetragonal crystal system (space group P4/mnc).
Key properties: Mohs hardness 3.5–4; specific gravity 2.99–3; Vitreous, pearly on the basal cleavage luster; optically uniaxial.
IMA symbol Cio, grandfathered status — known before the IMA’s founding, named in 1846.
Found in some granite pegmatites.
It is found associated with Topaz, phenakite, fluorite, cryolithionite, thomsenolite (Miass, Russia); cryolite, elpasolite, pachnolite, thomsenolite, ralstonite (Amelia, Virginia, USA).
Its name comes from the Greek for snow and stone, as compared to cryolite, ice-stone.