Source : Webster's Revised Unabridged Dictionary (1913)

Marcasite \Mar"ca*site\, n. [F. marcassite; cf. It. marcassita,
   Sp. marquesita, Pg. marquezita; all fr. Ar. marqash[=i]tha.]
   (Min.)
   A sulphide of iron resembling pyrite or common iron pyrites
   in composition, but differing in form; white iron pyrites.

   {Golden marcasite}, tin. [Obs.]