Source : Webster's Revised Unabridged Dictionary (1913)

Protometals \Pro`to*met"als\, n. pl.
   A finer form of metals, indicated by enhanced lines in their
   spark spectra (which are also observed in the spectra of some
   stars), obtained at the highest available laboratory
   temperatures (--Lockyer); as protocalcium, protochromium,
   protocopper, protonickel, protosilicon, protostrontium,
   prototitanium, protovanadium. -- {Pro`to*me*tal"ic}, a.