:Black yttrialite-(Y) with brown lustrous formanite-(Y) and brown britholite-(Y) with dull lustre. Locality: Lövböle, Kemiö Island, Southwestern Finland Region, Finland — Photo: Jyrki Autio · CC0
Yttrialite-(Y)
Yttrialite or Yttrialite-(Y) is a rare yttrium thorium sorosilicate mineral with formula: (Y,Th)2Si2O7. It forms green to orange yellow masses with conchoidal fracture. It crystallizes in the monoclinic-prismatic crystal system. It has a Mohs hardness of 5 to 5.5 and a specific gravity of 4.58. It is highly radioactive due to the thorium content. It is found associated with gadolinite. It was first described in 1889 for an occurrence in the Rode Ranch pegmatite on Baringer Hill, Llano County, Texas.
Intro adapted from Wikipedia (CC BY-SA).
Yttrialite-(Y) is an IMA-recognized mineral species in the silicate class, with the chemical formula Y₂Si₂O₇.
It crystallizes in the monoclinic crystal system (space group P2_1/m).
IMA symbol Ytt-Y, IMA status: approved, named in 1889.