The Collaborative International Dictionary of English v.0.48:

Paco \Pa"co\, Pacos \Pa"cos\, n. [Sp. paco, fr. Peruv. paco. Cf.
   Alpaca.]
   1. (Zool.) Same as Alpaca.
      [1913 Webster]

   2. [Peruv. paco, pacu, red, reddish, reddish ore containing
      silver; perh. a different word.] (Min.) An earthy-looking
      ore, consisting of brown oxide of iron with minute
      particles of native silver. --Ure.
      [1913 Webster]