Emily Dickinson Lexicon

PYR'ITE, n. [plur. Pyrites. Gr. πυριτης, from πυρ, fire.]

Fire-stone; a genus of inflammable substances composed of sulphur and iron or other metal; a sulphuret of iron or other metal. Hence sable coal his massy couch extends, / And stars of gold the sparkling pyrite blends. – Darwin. [I have anglicized this word, according to Darwin and the French mineralogists; making pyrites a regular plural.]