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The Mineral Iron Pyrite


Iron Pyrite mineral specimen

Chemistry: FeS2
Composition: Iron Sulfide
Class: Sulfides
Group: Pyrite
Crystal System: isometric
Fracture: conchoidal
Hardness: 6 - 6.5
Specific Gravity: apx 5.1+
Luster: metallic
Streak: greenish black
Color: brassy yellow
Cleavage: very indistinct
Transparency: opaque
Associated Minerals: calcite, fluorite, galena, gold, quartz, sphalerite and many others

Iron sulphide (46.6% Fe 53.4% S)
Bravoite is the name given to a nickel-rich iron sulfide. It is closely related to pyrite but contains up to 20% nickel. Pyrite's structure is analogous to galena's structure with a formula of PbS.


When tarnished pyrite might be confused with chalcopyrite, but it is harder and more yellow. Pyrite is difficult to distinguish from marcasite when a lack of clear indicators exists. pyrite is more slowly soluble in nitric acid than marcasite, giving a clear solution. Pyrite and Marcasite are polymorphs because both have the same chemical formula, FeS2, but both have different atomic structures. Pyrite has an isometric, cubic structure and Marcasite has an orthrohombic structure. Pyrite of coarse is harder than gold, and very brittle.
There are other shiny brassy yellow minerals that might be mistaken for gold. But pyrite is the most common and the most often mistaken for gold. Hence The name "Fools Gold". It also has a beautiful luster and interesting crystals. Pyrite is found in almost every possible environment, there for it has many forms and varieties. Pyrite is a frequent associate of all sorts of metal ores. In addition, it forms concretionary masses in sedimentary rocks. It is common in coal, and in slates and other metamorphic rocks. Pyrite can be altered to an oxide of iron, becoming limonite. Although pyrite is more stable than marcasite, pyrite is easily oxidized. Veins of pyrite are commonly found with overlaying cellular deposits of limonite called gossan. The ready oxidation of pyrite both disintegrates and stains. Making rocks containing pyrite ineffective for any structural purposes.

Pyrite is often crystallized, most frequently in striated cubes, less commonly in pyritohedrons or octahedrons. Massive pyrite is common. Crystal Habits include the cube, octahedron and pyritohedron (a dodecahedron with pentagonal faces) and crystals with combinations of these forms. Good interpenetration twins called iron crosses are rare. Found commonly in nodules. A flattened nodular variety called "Pyrite Suns" or "Pyrite Dollars" is popular in rock shops. Also massive, reniform and replaces other minerals and fossils forming pseudomorphs or copies.

Fuses easily. Becomes magnetic and gives off SO2 fumes. Insoluble in HCl, but a fine powder will dissolve in concentrated HNO3.

Fine specimens have been found throughout the world. Some of the more well know locations are Leadville, Colorado. Well developed crystal groups were found at Park City, Utah. Misshapen octahedral crystals containing 0.2% arsenic were found at French Creek, Pennsylvania. Other USA locations include Illinois and Missouri to name just a few. Complex, perfect crystals come from Elba, Italy. Falun, Sweden, yielded, a pyrite rich in cobalt. Many specimens today are coming from Peru. The specimens from Peru seem to be brighter and tarnish less easily. We have seen many mixed specimens from Mexico containing pyrite. Other famous localities include Germany; Russia; Spain; and South Africa along with many others.

A very minor ore of sulfur for sulfuric acid, used in jewelry under the trade name "marcasite" and as mineral specimens. Although pyrite is common and contains a high percentage of iron, it has never been used as a significant source of iron. However new technologies have opened the dor for it's use as an Iron Ore. But for now Iron oxides such as hematite and magnetite, are the primary iron ores. Pyrite is not as economical as these ores possibly due to their tendency to form larger concentrations of more easily mined material. Pyrite would be a potential source of iron if these ores should become scarce. Pyrite frequently has rich trace amounts of gold which can make it an important gold ore.

Name Origin: Greek, pyrite's lithos meaning "stone which strikes fire," in reference to the spark produced when iron is struck with a piece of pyrite

During WW II, the demand for sulfur kept increasing while the amount of native sulfur mined in North America kept decreasing. Native sulfur mines were becoming exhausted, making pyrite an attractive alternative economically. One large deposit near Ducktown, Tennessee began mining pyrite, pyrrohite and pentlandite exclusively for their sulfur contents.

Pyrite was first used to make sulfuric acid around 1000 AD. sulfuric acid is a very important acid in industry today. It is used to process almost any type of product you can think of.

Pyrite is commonly associated with quartz and fine mineral specimen of pyrite on quartz or quartz on pyrite, seem to be rather abundant. Pyrite inclusions in quartz on the other hand, seem to be quite rare.
Brazil has quartz included with pyrite. This quartz generally has massive looking little chunks of pyrite floating in it. Although some of it displays nice little cubes floating in it too. Iron oxide also commonly graces this material. Giving it interesting and beautiful yellow, orange and reddish orange streaks and clouds
Pyrite in Quartz gemstone

Pyrite in Quartz gemstone






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