Marcasite Stone

Marcasite is a semi-precious stone known for its unique, stained glass-like shine. It has a metallic luster with a greenish-yellow to brassy color and some say it appears to be fibrous when you look at it with a 10x powered loop.

Most people can recognize the name marcasite because it is used in inexpensive jewelry but the marcasite in jewelry is actually pyrite. Jewelers use pyrite because it doesn’t have the brittle characteristics marcasite has. I know this is getting confusing but keep reading to enhance your knowledge of marcasite.

While marcasite is a reasonably hard mineral (6-6.5 Moh’s hardness), they can’t be cut or polished into complex shapes but as you’ll see below when marcasite has a host rock then cabochons can be crafted from the slabs.

 

What Are Marcasite Stones?

Marcasite is an iron oxide that has the same chemical composition as pyrite. However, it has a radically different crystal structure. Unlike pyrite, marcasite doesn’t have a cubic identity. Instead, it crystalizes in a range of different shapes, including pyramidal, nodules, tabular, flakes, threads, and masses.

Both types of iron oxides are similar in color, with Marcasite having a lighter hue but pyrite has a higher luster. You can say without doubt marcasite is related to pyrite.

Marcasite is paler than Fool’s Gold, and it’s sometimes called white iron pyrite.

The low cleavage and orthorhombic crystal structure make marcasite too brittle to work with. So, when looking at jewelry you’ll notice the size of marcasite is very small and it doesn’t take on complex shapes.

 

 

What Does A Marcasite Stone Look Like?

Marcasites are orthorhombic – three axes at right angles and pyramid-like in shape. They grow in massive chunks with a brassy yellow color and metallic luster.

These opaque stones are iridescent in the right lighting but unlike other minerals, marcasite doesn’t have a refractive index and its hardness is between 6 to 6.5 on the Mohs scale.

The color of marcasite can be pale bronze yellow or a brassy color with grayish-green streaks and commonly cut into small rose cuts.

Marcasite jewelry is made using cut and polished pyrite. It is not, as the name suggests, genuine marcasite.

 

 

Green Marcasite

Green marcasite is yellowish-green marcasite crystals inside of chalcedony, agate, or jasper. The color green is seen in the host rock, not the actual marcasite crystal.

You’re probably wondering why rock and mineral dealers call it green marcasite if the color of marcasite is brassy. The truth is the industry loves to take something that is old and make it appear to be new. So, they use these one-off names to describe rocks and minerals when in reality it’s just marcasite. There’s nothing wrong with calling chalcedony or agate with marcasite inclusions but “Green Marcasite” has a better trade name.

 

 

Blue Marcasite

Blue marcasite is yellowish-green marcasite crystals inside of chalcedony, agate, or jasper. The color blue is seen in the host rock, not the actual marcasite crystal. As you can see from the image above the host rock maintains the blue color while the marcasite crystals are the metallic dots randomly scattered inside the cabochon.

You’re probably wondering why rock and mineral dealers call it blue marcasite if the color of marcasite is brassy. The truth is the industry loves to take something that is old and make it appear to be new. So, they use these one-off names to describe rocks and minerals when in reality it’s just marcasite. There’s nothing wrong with calling chalcedony or agate with marcasite inclusions but “Blue Marcasite” has a better trade name.

 

 

 

Black Marcasite

Black marcasite is yellowish-green marcasite crystals inside of chalcedony, agate, or jasper. The color black is seen in the host rock, not the actual marcasite crystal. Once again, you’ll notice the black background in the cabochon and the brassy inclusions scattered around.

You’re probably wondering why rock and mineral dealers call it black marcasite if the color of marcasite is brassy. The truth is the industry loves to take something that is old and make it appear to be new. So, they use these one-off names to describe rocks and minerals when in reality it’s just marcasite. There’s nothing wrong with calling chalcedony or agate with marcasite inclusions but “Black Marcasite” has a better trade name.

 

Marcasite Tumbled Stones

Tumbled marcasite is hard to find because of the chemical makeup of the mineral. When shopping at a local rock and mineral show you might come across tumbled stones labeled “tumbled marcasite” but the marcasite is an internal inclusion in chalcedony, jasper, or agate. These make really cool stones and are fairly affordable.