The Collaborative International Dictionary of English v.0.48:

Tantalum \Tan"ta*lum\, n. [NL. So named on account of the
   perplexity and difficulty encounterd by its discoverer
   (Ekeberg) in isolating it. See Tantalus.] (Chem.)
   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.
   [1913 Webster]