The Collaborative International Dictionary of English v.0.48:

Alquifou \Al"qui*fou\, n. [Equiv. to arquifoux, F. alquifoux,
   Sp. alquif['o]l, fr. the same Arabic word as alcohol. See
   Alcohol.]
   A lead ore found in Cornwall, England, and used by potters to
   give a green glaze to their wares; potter's ore.
   [1913 Webster]