Samarskite-(Y)
Kingman Feldspar Mine, Wallapai Mining District, Cerbat Mountains, Mohave County, Arizona, USA
Tucson Mineral and Gem rubble pile.
Si-PIN XRF shows mainly Fe, Y and Nb. This and other physical characteristics (hardness 5.25, small prismatic crystals, conchoidal fracture, black internal color) seems to indicate samarskite-Y.
According to mindat, due to cation ordering Fe is written separately in the formula; it is an essential ...