Whitish and yellowish crystals of the very rare yttrium mineral tveitite-(Y) from a locality in Russia (Rovgora Mountain, Western Keivy Massif, Keivy Mountains, Murmansk Oblast, Russian Federation). Ex. Erich Laskowski collection (USA). — Photo: David Hospital · CC BY 4.0
Tveitite-(Y)
Tveitite-(Y) is an IMA-recognized mineral species in the halide class, with the chemical formula (Y,Na)₆(Ca,Na,REE)₁₂(Ca,Na)F₄₂.
It crystallizes in the hexagonal crystal system (space group R-3).
Key properties: specific gravity 3.94; Greasy luster; optically biaxial.
IMA symbol Ttt-Y, IMA status: approved, named in 1975.
Found in a pegmatite dike in amphibolites, probably formed by inversion of yttrofluorite.
It is found associated with Kainosite, fluocerite, cerianite, monazite, beryl, topaz, muscovite, microcline, quartz.
The mineral was named to honor John Tveit, in whose quarry in Norway the mineral was first found.