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Marcasite Gemstones - Also called the White Iron Pyrite

Introduction

Marcasite is a mineral which is also called the White Iron Pyrite. It is classified as iron sulfide, (FeS2), which has a crystal structure that is orthorhombic. However, it has a different physical and crystalline structure from pyrite, which is actually the same element, but one with a cubic crystal structure. The main similarity between the two minerals is the fact that they all contain disulfide ions; these are ions that have a very short bonding distance between the atoms of sulfur in the crystal. However, their two structure differ in the way the di-anions are placed within the Iron cat-ions. This makes Marcasite to be much lighter and brittle when compared to pyrite. It is easy to find marcasite crumbling and breaking at the slightest pressure due to an unstable structure within the crystal.

Marcasite has a fresh surface that has a pale yellow color, and this can range to almost white. This is a gemstone that has a very metallic luster which is very bright. After the surface is exposed to the elements for a while, it turns into a yellow to brown color, which may sometimes have a black streak. Although the material is brittle, it is resistant to scratches and cannot be affected by a knife. The crystals have a thin and flat, tabular structure and when found in groups, they are called cockscombs.

Today, when you walk into a jewelry store, you should be aware that not every gemstone that is labeled as marcasite is actually made of this mineral. Due to the similarity in their outward appearance, you may find jewelry, labeled as marcasite jewelry, which is actually made out of pyrite. During the late medieval period, and also part of the early modern times, the word marcasite was used to both cover marcasite and pyrite. However, in 1845, scientific examination of the structure of the crystals gave rise to the name marcasite being given to the orthorhombic structured mineral, while pyrite was given to the cubic structured one. However, the term marcasite was used prior to this definition. Today, any marcasite jewelry is actually made of pyrite, and the reason for this is because actual marcasite is too brittle to be worked into jewelry.

Marcasite has been found to form as both a primary and secondary mineral, and these formations are found under low-temperature and acidic conditions. The mineral is primarily found in sedimentary rocks such as limestone, shale and low-grade coal. It is also found in hydrothermal veins that are in low-temperature conditions. This is a mineral that is commonly associated with pyrite, as the major one, and also calcite, dolomite, galena, pyrrhotite, fluorite and spharelite.

When it is formed as the primary mineral, it is found in concretions, crystals ad nodules, within several types of sedimentary rocks, and these are mainly found in areas such as Dover, in Kent, England; here it is found in sharp singular crystals, and sometimes in crystal groups as well as nodules in the chalk. When it is found as a secondary mineral, it is formed due to the chemical alteration of Chalcopyrite and Pyrrhotite.

Under conditions of high humidity, Marcasite reacts much more easily than pyrite, and this reaction gives rise to iron sulfate and sulfuric acid. The white powder that forms on the surface of the hydrous iron sulfate is known as melanirite and has the chemical formula of FeSO4.7H2O.

The way in which Marcasite breaks down when exposed to humidity, affecting other minerals which may be next to it in a collection, is referred to as “Pyrite Decay”. The oxygen and moisture in the air, react with the marcasite exposed at the surface, making the sulfur to oxidize and the combine with the water to make sulfuric acid. This acid then attacks the other sulfide minerals and other minerals in the collections. It is advised that marcasite is stored in environments that have less than 60 percent of humidity in the air, as this slows, or completely stops, this reaction.

The ancient Greeks were known to make marcasite jewelry, but this was really pyrite, since it is harder and better suited for working. The 18th century was inundated with jewelry and other decorative items made of this metal, and it was especially prominent in the Victorian Era and during the Art Nouveau jewelry design period. Usually, the small piece of pyrite are mixed in with silver, which is the best setting given the metallic look of pyrites. Costume jewelry, which is quite cheap, is made by putting pieces of pyrite together using glue instead of setting the pieces in silver. It is also possible to recreate the same type of jewelry, using small pieces of steel, which will not corrode. Another name for pyrite is fool’s gold, due to the bright yellow look of the polished metal, before it gets corroded.

Looking at Marcasite gemstones closely

Marcasite is a mineral that is not as well-known as its companion Pyrite. Both of these minerals have the same chemical formula, but they all crystalize in a different manner, and this gives them different physical properties, namely, hardness. It is possible for dealers to make mistakes when they are labeling iron sulfide minerals without subjecting them to complex analysis. This leads to some specimens being labeled as pyrite when they are actually marcasite, and vice versa. However, it would be great to know that marcasite is never used as a gemstone, and any piece of jewelry that is marketed as marcasite is actually made of pyrite.

Marcasite is one of the minerals that is most susceptible to what is called pyrite decay. This is a condition that comes about when some sulfides are exposed to air, with marcasite, the humid air will form a white powder on the surface of the mineral. Very little is understood about why this happens only after the mineral is mined. The surface of the metal reacts with the air, and release sulfur atoms. These then combine with the water in the humid air to form sulfuric acid. Now, when this stone is in the presence of other gemstones or minerals that are made of sulfides, they are also attacked. This is one of the reasons why they should be stored separately, or removed from collections when it begins to decay.

One of the odd things is that some of these minerals will not be affected by humidity while others are. In fact, it has been seen that some minerals from certain localities are more prone to this decay than other localities.

Chemical properties of Marcasite gemstones

It has the chemical formal of Iron Sulfide or FeS2, and has a pale yellow color, which can range to white. It can be tarnished to form a brass-brown color and other iridescent colors. It streak from dark brown to black, and the streak has a slightly green tint. The gemstone has a hardness of 6 to 6.5 and has an orthorhombic crystal system and aggregates into the usual bi-pyramidal and tabular crystals; these are given the names of coxcomb aggregates and bladed. The crystals can also form a structure that looks like a herringbone. They can also occur as mammillary, radiating nodular, encrusting and massive groupings. They can also be in the form of small crystals, and sometimes in what are known as dollars, which are simple many radiating discs, resembling a pile of dollars. The crystals also form as pseudomorphs covering other fossils and minerals, and this brings about odd shapes and forms.

Marcasite is opaque, and has a specific gravity of 4.8 to 4.9. It has a brilliant metallic luster, and has a conchoidal fracture and a prismatic cleavage. These factors make marcasite very brittle and it is not suitable for the making of jewelry. It is mainly found in sedimentary deposits, or low temperature ore veins; these are also called skarn metamorphic deposits.

Some notable localities of Marcasite gems

Marcasite is found in many places in Europe, and these include Bohemia, Czech Republic, Olkusz in Poland and the Maramures Company, Baia Mare, all in Romania. This mineral is also one of the most important mineral exports from Panasqueira, in Portugal. One can also find marcasite deposits on the chalk cliffs that line the shores of France and England, especially the areas of Cap Blanc-Nez, Pas-de-Calais, Kent and Dover.

One of the most excellent and abundant places to get marcasite is the United States of America. The gemstone is found mainly in the Midwest. The regions are so many and vast.

Common Associations of Marcasite

There are several associated minerals to marcasite and these are Dolomite, Spharelite, Bornite, Quartz, Chalcocite, and Galena. Here are some of the common ways to differentiate between the closest of these associations:

  • Chalcopyrite has a lower hardness than marcasite but it has a denser yellow color.
  • Cobaltite is also less hard than marcasite, but it is whiter in color and has a different crystal formation.
  • Pyrite is the most similar association, but is has a difference in the crystal formation. When the crystals ate indistinct, you cannot distinguish between the two.
  • Pyrrhotite has a lower hardness, but it is dark yellow in color, and is attracted to magnets.
Now that it is known that marcasite jewelry is actually made of pyrite, you may want to know a little more about it.

A little more about pyrites

For thousands of years pyrite has been used in the making of jewelry; the Inca, Greeks and Romans are some of the notable civilizations which used this metal for purposes of adornment. Today, it may not be as popular, but collectors will pay a handsome price for a well-designed piece. Pyrite, on its own, is rarely used as a gemstone, and is usually used as a base metal on which another jewel is placed. It is used under the name of marcasite when actually used as the main decorative gemstone in a jewelry piece. The quality of gemstone that is used for the purpose of making jewelry under the name of marcasite, has to be very high.

What is pyrite?

This is a gemstone, which was named after the Greek word Purites, which actually means fire. This gemstone is also called Iron Pyrite, or Marcasite. The name came from the fact that when the gemstone is hit against steel, it will produce sparks.

Pyrites have a strong resemblance to gold, due to the yellowish metallic shine that it exhibits, and this led to it being called Fool’s Gold. This is a gemstone that has a hardness value of 6 to 6.5 on the Mohs scale, which makes it a very hard gemstone, although it is not as hard as a sapphire of diamond.

Pyrite has a strong ferromagnetic ability, but it is a very weak paramagnetic. This means that on its own, it cannot act as a magnet, but it will exhibit magnetic ability when it is placed in a magnetic field. The term magnetic pyrite is not used correctly because it does not refer to real pyrite; it refers to a polymorph of pyrite called pyrrhotite.

Pyrite is an iron sulfide with the chemical formula of FeS2 and it is a common gemstone that can be found in many places in the world. However, the high quality pyrite rough can only be found in less than a dozen countries, of which the United States of America is a major producer.

Pyrite must be mined with great care, because it oxidizes when it comes into contact with humid air, and one of the products is sulfuric acid. This acid can seep into the ground and surroundings causing a lot of environmental damage. Another dangerous trend of this metal is that I can spontaneously burst into fire when it is left in the air for too long. This is similar to the way magnesium burns in air, and has to be stored in oil. The best way to avoid both these hazards is to seal the mine when it is not is use.

What is marcasite?

If you have never seen pyrite jewelry, it is probably because pyrite jewelry is marketed as marcasite jewelry. Marcasite has the same chemical formula as pyrite, and even has the same look, but there are some differences that set them apart. The crystal structure of marcasite is such that it is lighter and more brittle, therefore it breaks more easily. In the past, the term Marcasite was use for both metals but in 1845, this difference was discovered and they had to be classified as different minerals.

Despite this distinction, the jewelry world did not seem to get on board. Even if all the jewelry being sold as marcasite is actually pyrite, the distinction was never brought into the market. This is acceptable, since pyrite is still the only of the two, that can be used to make jewelry and it was important to keep the marcasite named alive.

There are other minerals which look like pyrites and these are Chalcopyrite, which has a deeper yellow with green tones, and is quite soft, with a value of 3.5 to 4 on the Mohs scale. Arsenopyrite looks more like bright steel or white silver, but it is only used for the extraction of arsenic. True marcasite has never been used to make jewelry and the only way that one can have it is to look for it, in its rough form, and then keep it safely, and out of humidity, in a mineral or rock collection.

The uses of pyrites

Pyrites are mainly used for is for personal adornments, and also other items that can be kept in the house. Pyrite, throughout history, have never been used for any other purpose. When it was discovered, it was used to make copperas, which is iron sulfate, and they did this by burning the pyrite, or letting g it rust. In the early days, when the gun was designed, pyrites were used to create the spark that was needed to light the gun powder, and propel the projectile forward, but this was soon replaced by other methods.

Another use of pyrites was as a mineral detector, and they were placed in the first radios. Today, some people who love using crystal radios as a hobby, still look for pyrites for the radios. It is as sensitive as most modern mineral detectors, but its use was very expensive, and could not be relied upon accurately.

Taking care of pyrite or marcasite gemstones

It is common knowledge that most jewelry that is marketed as marcasite is actually pyrite, and this is the reason why the topic above mentions pyrite, instead of marcasite.

Pyrite is very brittle, and one should take extra caution when handling any jewelry made from this material. If you have any jewelry made of this mineral here are a few ways in which you can ensure that it has a long, unblemished life:

Always clean the jewelry with warm water, some spa, and then use a chamois cloth to dry it. You should never use steam, hot or boiling water, jewelry cleaning solutions or ultrasonic baths; these cleaning methods will ruin the integrity of the stone, and may actually cause it to lose its fine looks.

Store the gemstone in a dark place, preferable in a lined case that can be shut.

The gemstone should be stored on its own, and away from other gemstones, which may actually scratch its soft surface.

How to buy Marcasite

This actually means how to buy jewelry that is made from pyrite. You will find that marcasite jewelry is quite affordable and goes for the same price as silver jewelry. You will find several simulants that are used to imitate marcasite, such as steel. The fraud perpetrated on marcasite jewelry is inconsequential compared to the fraud that involves other types of jewelry.

However, when it comes to buying marcasite jewelry that has been included in other gemstone collections, then there is the possibility of getting fraudulent marcasite claims. Therefore, you have to follow any advice on how to detect fraud, involving the other jewelry, which may be in the same design with the marcasite.

When buying loose marcasite, you will find it in the form of decorations, and these will be items such as large pyrite balls, mineral collections, and in some jewelry pieces. The prices available will depend on several factors, making them fluctuate from a few dollars to hundreds of dollars; the quality of the marcasite being used will determine the price of the item being bought. If the mineral has visible crystals or cubes of marcasite/pyrite, then you will have to pay high prices for it.

In summary, the story and profile of marcasite jewelry is very interesting given that all of it is actually pyrite, but marketed as marcasite; what of marcasite and its mineralogical uses? There is still a lot of research that is being done on the uses of marcasite, especially in the world of gemology. Designers are still looking for ways in which they can use the actually marcasite, but there is very little advancement to this end. The future is still hopeful for this unlikely gemstone.



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