What is Marcasite?

Tricia Christensen
Tricia Christensen

Marcasite is a mineral formed from iron sulfate. It is occasionally called white pyrite, but is not pyrite, or fool’s gold, as it is sometimes called. To further confuse matters, most gems called marcasite, are in reality pyrite. True marcasite disintegrates quickly and does not keep well in gem form.

Those who make their own jewelry often enjoy using pyrite because of its lovely appearance and low cost.
Those who make their own jewelry often enjoy using pyrite because of its lovely appearance and low cost.

The non-gem marcasite is yellow and may exhibit some green tints. It may also have white or brown colorations. It is a relatively soft stone with a hardness of approximately 6-6.5 on the Moh’s Hardness scale. It forms into what are called coxcomb aggregates, where the crystals are separated into crystals that are similar in shape to the head of a top of a rooster’s head. Because of this special formation, marcasite is prized in collections.

Unfortunately, collected marcasite deteriorates gradually, possibly as a result of bacteria. Bacterial agents found abundantly in the air may facilitate the breakdown of iron sulfate. Eventually, a piece of marcasite will completely deteriorate into white powder. One decaying marcasite may affect other minerals close to it. Marcasite specimens tend to be separated to slow down decay of this delicate but attractive mineral.

Marcasite gems or pyrite are steeped in lore and tradition. They are thought to be able to discharge negative energy, improve one’s communication abilities, and protect those who perform dangerous jobs. Such lore tends to be the result of pagan traditions.

Miners, however, often viewed pyrite negatively since it had a deceptive appearance, which many mistook for gold. Many based their opinions on where to dig or pan based on pyrite, and too late learned that these stones were worthless. Thus it inherited the name fool’s gold.

Today marcasite/pyrite gems are of value because they are an attractive black that appears iridescent in the light. They are also very inexpensive, with loose stones of several carats usually less than one US dollar (USD). Those who make their own jewelry often enjoy using pyrite because of its lovely appearance and low cost.

Tricia Christensen
Tricia Christensen

Tricia has a Literature degree from Sonoma State University and has been a frequent wiseGEEK contributor for many years. She is especially passionate about reading and writing, although her other interests include medicine, art, film, history, politics, ethics, and religion. Tricia lives in Northern California and is currently working on her first novel.

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Discussion Comments


If marcasite can deteriorate so rapidly, how does it form and in what environment? Is there any way to prevent it from deteriorating?

This sounds like it would make such cool jewelry, but I would hate to get some if it was just going to crumble into dust!


I have silver Marcasite rings and was wondering what they was made of.


So this sounds like it is basically a fools fools gold, since it is mistaken for fools gold, which is mistaken for gold. How sad for these "fools" to get their hopes up so high when discovering these materials, only to discover later that they are relatively worthless compared to real gold.


completely informative! thank you.

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