Tantalum

A rare nonmetallic element found in certain minerals, as tantalite, samarskite, and fergusonite, and isolated as a dark powder which becomes steel-gray by burnishing. Symbol Ta. Atomic weight 182.0. Formerly called also tantalium.

a hard grey lustrous metallic element that is highly resistant to corrosion; occurs in niobite and fergusonite and tantalite