Pyrite and Marcasite: Fool’s Gold
Pyrite has been used in jewelry for thousands of years and was used by the ancient Romans, Greeks and Inca’s among others. Today its star has faded and is mostly sold to collectors.
Pyrite’s use as a gemstone in jewelry is fairly limited, it is mostly used as the metal in which another gemstone is placed.
High quality pyrite however is still beautiful enough to form the focal point of your jewelry. When used in jewelry it is almost always under the name marcasite.
What is Pyrite?
Pyrite, also known as iron pyrite or marcasite, got its name from the Greek word ‘purites’ which means fire. Alluding to the fact that when you strike it against steel it will create sparks.
Because pyrite resembles gold, with its yellow metallic shine, it was given the nickname fool’s gold. It scores between 6 and 6.5 on Mohs hardness scale, which makes it a fairly hard crystal, though far below sapphires or diamonds.
Pyrite is weakly paramagnetic, but not ferromagnetic, which means it is not attracted to a magnet, but is able to act as a magnet when a magnetic field is applied to it.
Magnetic pyrite as the name says is indeed weakly ferromagnetic, but actually is not pyrite at all! It’s another iron sulfide mineral with the name pyrrhotite.
The chemical formula for pyrite is FeS2 and it is an iron sulfide. As a quite common mineral it can be found all over the world. High quality ore however is slightly more limited and is currently mined in less than a dozen countries including the USA.
Pyrite will oxidize when it comes into contact with the atmosphere, leading to acid mine drainage, which can cause great harm to the environment. Another problem is that pyrite can actually spontaneously combust when exposed to air for longer periods. Usually both these problems are solved by sealing the mine or shaft when it is no longer in use.
What is Marcasite?
It’s possible you’ve never seen pyrite jewelry, this is because it is incorrectly called marcasite jewelry. Marcasite resembles pyrite and even has the same chemical formula.
The different crystal structure means that it is lighter and breaks more easily. Marcasite used to mean both pyrite and marcasite, however in 1845 it was redefined.
For some reason this was never changed in the jewelry world. And all jewelry that being sold under the name marcasite is actually pyrite jewelry. Which is just as well, because pyrite is far more suitable for jewelry than marcasite.
Other minerals that look like pyrite are Chalcopyrite, which is slightly more yellow with some green tones. It has a hardness of only 3.5 to 4 on Mohs hardness scale. Arsenopyrite has a steel or silvery white color and is mostly used as an arsenic ore.
Real marcasite is never used as a gemstone, you will only find real marcasite if you actively search for it for a mineral or rock collection.
The most obvious use of pyrite is as a gemstone to be used in jewelry or for other decorations. However throughout its history pyrite has had quite a few other uses:
Since it was discovered it has been used to make copperas (iron sulfate), either by letting it weather (letting it rust) or by burning it.
Early firearms used pyrite to create the spark that was needed to fire the gun, though it was quickly replaced by other methods.
Pyrite was used as a mineral detector in early radio’s and is still in use by some hobbyists that own a crystal radio. While still as sensitive as most modern detectors it has been replaced because of cost and reliability.
Taking Care of Your Pyrite Gemstones
Pyrite can be quite brittle and you should be careful when handling it. Here’s several tips to keep your pyrite (or if you prefer, marcasite) jewelry in good shape.
Cleaning should be done with warm water, some soap and a soft cloth to dry. Jewelry cleaner, hot or boiling water and steam or ultrasonic jewelry cleaners should never be used. They can cause a lot of damage and possibly ruin your stone or jewelry.
Store it in a dark and cool place away from jewelry or other hard objects. As it can be scratched fairly easy by most faceted gemstones.
Marcasite Buying Guide
For this guide pyrite will be referred to as marcasite because it’s the name under which almost all pyrite jewelry is sold. Marcasite jewelry is pretty inexpensive, usually selling for about the same as silver jewelry.
There are simulants on the market such as steel. However most fraud is focused on more lucrative gemstones. Because of this you can be fairly certain that you are buying real marcasite.
The main problem comes when marcasite jewelry is combined with gemstones that are enhanced or imitated on a larger scale. But those particular pitfalls are too broad to be properly discussed in this article. Please refer to articles of individual gemstones which will? have a buying guide or buying advice towards the end.
Loose pyrite is mostly sold as decorations, such as larger balls of pyrites, or for gemstone and mineral collections. Prices for these vary wildly, from just a few dollars for lower quality minerals to hundreds of dollars for larger high quality minerals. Especially if the mineral has visible pyrite cubes or pyrite crystals you can expect to pay a premium.