| Noun | 1. | fergusonite - a dark mineral consisting of oxides of yttrium and erbium and tantalum and other mineralsatomic number 73, Ta, tantalum - a hard gray lustrous metallic element that is highly corrosion-resistant; occurs in niobite and fergusonite and tantalite atomic number 39, Y, yttrium - a silvery metallic element that is common in rare-earth minerals; used in magnesium and aluminum alloys mineral - solid homogeneous inorganic substances occurring in nature having a definite chemical composition | |