Marcasite, spelled also marcassite, marchasite, marquesett, or
marquaset, was a mineral, the crystallized form of iron pyrites. It
was largely used in the eighteenth century for various ornamental
purposes, chiefly in the decoration of the person. It took a good
polish, and when cut in facets like a rose-diamond, formed a pretty
material for shoe and knee-buckles, earrings, rings, pins, and hair
ornaments. Scarce a single advertisement of wares of milliner or
mantua maker can he found in eighteenth century newspapers that does
not contain in some form of spelling the word marcasite, and scarce
a rich gown or headdress was seen without some ornament of
marcasite.