Gadolinite, sometimes also known as Ytterbite, is a silicate mineral that consists principally of the silicates of cerium, lanthanum, neodymium, yttrium, beryllium, and iron with the formula (Ce,La,Nd,Y)₂FeBe₂Si₂O₁₀. It is called gadolinite-(Ce) or gadolinite-(Y) depending on the prominence of the variable element composition (namely, Y if it has more yttrium, and Ce if it has more cerium). It may contain 35.48% yttria sub-group rare earths, 2.17 eria earths, up to 11.6 eO and traces of thorium. It is found in Sweden, Norway, and the USA (Texas and Colorado).