Material: 925 Sterling Silver, Marcasite, Ruby like Pink Synthetic Stone US size 8 Marcasite Trivia: Marcasite is a genuine, natural gemstone, which is derived from a natural mineral called 'pyrite'. Pyrite is found in many parts of the world, but only a small fraction of it is suitable for the cutting processes required to create marcasite jewelry. Marcasite is both an elegant and fashionable gemstone.