Obs. A former name of iron pyrites or Marcasite.
1640. Jrnl. Ho. Commons, II. 33. The Patent concerning Coporis Stones.
1652. French, Yorksh. Spa, vi. 58. Take Copperas stone, which is a certain Sulphurious glittering Marcasite.
1694. Slare, in Phil. Trans., XVIII. 218. He was Master of a Copperas Work at Whitstable in Kent, and engrossed all the Pyrites or Copperas-stone.
1776. Seiferth, trans. Gellert’s Metal. Chym., 497. Pyrites, or Copperas-stone.
