Pyrite \Pyr"ite\, n.; pl. Pyrites. [Cf. F. pyrite. See Pyrites.]

(Min.) A common mineral of a pale brass-yellow color and brilliant metallic luster, crystallizing in the isometric system; iron pyrites; iron disulphide.

Hence sable coal his massy couch extends, And stars of gold the sparkling pyrite blends. --E. Darwin.

Source: Webster's Revised Unabridged Dictionary (1913)