gadolinite

noun

1. a silicate mineral from which the rare-earth metals gadolinium, holmium, and rhenium are extracted.

noun

1. a rare brown or black mineral consisting of a silicate of iron, beryllium, and yttrium in monoclinic crystalline form. Formula: 2BeO.FeO.Y 2 O 3 .2SiO 2Also called: ytterbite