Marcasite is an interesting mineral that has been confused with other types of minerals for generations. Marcasite, which is sometimes called white pyrite or white iron pyrite is created from iron sulfide. Its chemical make up is FES2. Marcasite is closely associated with Pyrite, but more likely than not usually those that think they are buying Marcasite are actually buying pyrite.
This problem arises form the unique chemical make up of Marcasite. Marcasite includes the exact same chemicals as Pyrite, except for the fact that they are arranged differently. While they might somewhat similiar, their inherent qualities are different. Marcasite for instance, will be extremely brittle and will crumble quite easily. It is also sometimes recognized by being lighter than pyrite.
Marcasite is usually yellowish or has a brassy look to it. It can sometimes include the color of green. There is an interesting effect that can occur in Marcasite, it is called the Cox’s comb. It is a crystal twinned habit. This occurs when the crystals appear to form the head of a rooster; it is very distinctive and unique only to Marcasite.
While Marcasite has been known for thousands of years to the Greeks, Mayans and Chinese, most mythology is associated with its Pyrite type properties. For instance, Marcasite is seen as having a calming effect, as well as a healing effect. In fact, many cultures viewed Marcasite and its cousin Pyrite as a healing stone or to attract wealth or inspire creativity.