Well formed groups of pale yellow acicular crystals of the extremely rare fogoite-(Y) (IMA 2014-098) from the type and only known locality worldwide: Agua de Pau Volcano, San Miguel Island, Azores District, Portugal. Fogoite-(Y) is a Yttrium-Titanium silicate and it is the second new mineral from the locality after chiappinoite-(Y). — Photo: David Hospital · CC BY-SA 4.0
Fogoite-(Y)
Fogoite-(Y) is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₂Y₂Na₃Ti(Si₂O₇)₂(OF)F₂.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Seidozerite-Rinkite structural group.
Key properties: Mohs hardness 5; specific gravity 3.523; White streak; Vitreous luster; optically biaxial.
IMA symbol Fog-Y, IMA status: approved, named in 2014.
Found in miarolitic cavities in a syenite xenolith in trachytic ejecta from a stratavolcano.
It is found associated with Sanidine, astrophyllite, fluornatropyrochlore, ferrokentbrooksite, quartz, ferrokatophorite.
The name refers to the Fogo volcano, São Miguel Island, the Azores, where the first specimens were collected.