Samarskite-
>
&h=867&w=768&tbnid=u07pRPdsqZoN_M&q=Samarskite-&tbnh=239&tbnw=211&usg=AI4_-kSo0tiMO-8vpNXhmnXSZd1SYet2WQ&vet=1&docid=8ijtIFUZ_fC24M&itg=1&sa=X&ved=2ahUKEwiO-_3L--CFAxW7ha8BHSEtAY4Q9QF6BAgAEAM)
Samarskite is a radioactive rare earth mineral series which includes samarskite-(Y), with the chemical formula (YFe³⁺Fe²⁺U, Th, Ca)₂(Nb, Ta)₂O₈ and samarskite-, with the chemical formula (YbFe³⁺)₂(Nb, Ta)₂O₈. The formula for samarskite-(Y) is also... Wikipedia
Crystal class: Dipyramidal (mmm); H-M symbol: (2/m 2/m 2/m)
Crystal habit: Crystals elongated with pyramidal terminations; commonly granular to massive
Crystal system: Orthorhombic
Formula (repeating unit): (YFe3+Fe2+U,Th,Ca)2(Nb,Ta)2O8
Mohs scale hardness: 5–6
Optical properties: Appears isotropic
Space group: Pbcn