Yellow/brown crystals of the extremely rare mineral mieite-(Y) from the famous Ytterby deposit in Sweden and associated to keiviite-(Y) and fergusonite-(Y) after the original label of the Vandenbroucke Museum. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Mieite-(Y)
Mieite-(Y) is an IMA-recognized mineral species in the silicate class, with the chemical formula Y₄Ti(SiO₄)₂O[F,(OH)]₆.
It crystallizes in the orthorhombic crystal system (space group Cmcm).
Key properties: Mohs hardness 6; specific gravity 4.61; White streak; Adamantine luster; optically biaxial.
IMA symbol Mi-Y, IMA status: approved, named in 2014.
Found in a block of granitic pegmatite collected from a talus slope.
It is found associated with Quartz, albite, K-feldspar, muscovite, allanite-(Ce), gadlinite-(Y), magnesiorowlandite-(Y).
The name refers to the prefecture in Japan that produced the first specimens.