资料来源 : Webster's Revised Unabridged Dictionary (1913)

Almagra \Al*ma"gra\, n. [Sp. almagra, almagre, fr. Ar.
   al-maghrah red clay or earth.]
   A fine, deep red ocher, somewhat purplish, found in Spain. It
   is the {sil atticum} of the ancients. Under the name of
   {Indian red} it is used for polishing glass and silver.