:Locality: Katugin, Chitinskaya Oblast', Transbaikalia, Eastern Siberia, Russian Federation Size: 1.4 × 1.1 × 0.7 cm Description: Brick-red sample of gagarinite-(Y), showing crystalline shape, embeded in cryolite and sugar fluoraluminates like thomsenolite or gearksutite. — Photo: Joan Rosell , from rosellminerals.com · CC BY-SA 4.0
Gagarinite-(Y)
Gagarinite-(Y) is an IMA-recognized mineral species in the halide class, with the chemical formula NaCaYF₆.
It crystallizes in the hexagonal crystal system (space group P6_3/m). It is a member of the Gagarinite structural group.
Key properties: Mohs hardness 4.5; specific gravity 4.11–4.29; White streak; Vitreous to dull luster; optically uniaxial.
IMA symbol Gag-Y, IMA status: approved, named in 1961.
Occurs as disseminations, segregations, and in veins and miarolitic cavities within Na-metasomatized alkalic granites and quartz-syenites.
It is found associated with Riebeckite, pyrochlore, zircon, bastnäsite, tengerite, synchysite, yttrofluorite, elpidite (Verkhne-Espe massif, Kazakhstan); riebeckite, aegirine, zircon.
In honor of the first cosmonaut, Yuri Alekseevich Gagarin (1934–1968).