Euxenite-(Y) Locality: Besakoa (Besekoa), Madagascar ( Locality at mindat.org ) Size: 5 cm x 3.8 cm x 2.4 cm Euxenite-(Y) is an uncommon rare earth oxide containing numerous rare earth elements and is found in granite pegmatites. This is a sharp, well-formed, tan, floater, parallel-growth crystal with a chisel termination. This is a fine old-time piece. Accompanied by a N. Boubee label dating to before 1937. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Euxenite-(Y)
Euxenite, or euxenite-(Y) (the official mineralogical name), is a brownish black mineral with a metallic luster.
Intro adapted from Wikipedia (CC BY-SA).
Euxenite-(Y) is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula (Y,Ca,Ce,U,Th)(Nb,Ta,Ti)₂O₆.
It crystallizes in the orthorhombic crystal system (space group Pbcn). It is a member of the Columbite structural group.
Key properties: Mohs hardness 5.5–6.5; specific gravity 5.3–5.9; Yellowish, grayish, or reddish brown streak; Brilliant submetallic, waxy to resinous on fractures luster; refractive index 2.152; optically isotropic.
IMA symbol Eux-Y, IMA status: approved, named in 1840.
From granite pegmatites; as a component of detrital black sands.
It is found associated with Albite, microcline, biotite, muscovite, ilmenite, monazite, xenotime, zircon, beryl, magnetite, garnet, allanite, gadolinite, aeschynite-(Y), thorite.
Its name comes from the Greek for hospitable, in allusion to the wide variety of rare elements in its composition.