There is some bewilderment over what should accurately be called Marcasite. Initially the name Marcasite was applied by mineralogists to an unbalanced form of iron sulphide crystallising in the rhombic system. The Marcasite found in jewellery is also iron sulphide, with the same chemical composition, but crystallising in the cubic system. Both forms are also called pyrites or iron pyrites.

Pronunciation: Marcasite should be pronounced "markazeet", not marquisite, and pyrites should be pronounced "pie-right-eeze", not "pie-rights".

Marcasite is usually described is being a fair bronze colour, we think it looks rather silver - greyish.
It seems bizarre that Marcasite should have imitations, as it is inexpensive, but glass, steel and plastic have all been used as imitations.
Marcasite is regularly found in reasonably priced silver jewellery and watches. It was fashionable and popular in Victorian and other times. Marcasite is vulnerable to damage if knocked or dropped, but otherwise is quite suitable for jewellery use. It is often used to imitate diamonds. In better quality jewellery it is hand-set with grains or beads of metal from the setting being pushed over the edges of the stones, in cheaper jewellery it is sometimes glued into place, making it more susceptible to loss.