Pyrite (S2Fe) (iron sulfide) is a mineral belonging to the group of sulfides. It is considered a very common mineral because it forms in igneous, sedimentary and metamorphic rocks, in addition, it also occurs in various hydrothermal environments associated with vein deposits, copper porphyries and volcanogenic massive sulphides mainly.
In addition, pyrite is a very famous mineral because many times mineral explorers and gold explorers without much experience confuse this mineral with the precious metal.
Where is pyrite is there gold?
The pyrite It is important because when it is of hydrothermal origin, it usually has small amounts of gold (around 0.25% of the total volume), which may not seem like much, but can be extracted metallurgically and generate a high economic impact on mining companies.
Where there is pyrite there is not always gold, however it is recognized that when the pyrite is in hydrothermal and vein environments, it is very likely to find gold.
Properties and Characteristics of the mineral pyrite
The pyrite It is an iron sulfide that is characterized by having a pale brassy yellow color and sometimes dark gray when oxidized (oxidized pyrite), in addition, it has a very characteristic resplendent metallic luster and the color of its stripe is dark black or dark green to brown.
Its hardness (between 6 and 6.5) is high if we compare it with other sulfides, and this is not very common in nature, in addition, it has a specific weight of approximately 5.02 g/cm3.
| Pyrite | Physical and chemical properties |
|---|---|
| class, group | Sulfides (iron sulfide). |
| Chemical formula | FeS2 |
| Chemical composition | Fe (45.6%), S (53.4%). |
| Fracture | conoidea. |
| Tenacity | Fragile. |
| Mohs hardness | 6 to 6.5 (it is high compared to other sulfides). |
| Density or specific weight | 5.02 g/cm3. |
| Brightness | Shimmering metallic. |
| Color | Pale brassy yellow, but may be dark gray due to patinas. |
| Stripe | Black, greenish-black to brown. |
| cleavage | does not present |
| crystalline system | Cubic. |
| Polymorphous | the marcasite |
| Way of presenting or habit | Cubic and twelve-sided crystals, massive, granular or elongated. |
| associated rocks | Shales, pegmatites, phyllites, shales, skarns, limestone and calcareous rocks, coal. |
| Origin and geological environment | Hydrothermal, oxygen-depleted and magmatic environment. It is also associated with gold. |
| Associated minerals | chalcopyrite, galena, sphalerite, stibnite, cinnabar, argentite, calcite, marcasite, quartz etc. (it is a ubiquitous mineral). |
| Applications | Associated with gold and copper, sometimes iron ore, and sometimes to produce sulfur and caprosa. |
It does not show cleavage, so its fracture is conchoidal and it breaks brittle.
As for its chemical composition, it has iron Fe (45.6%), sulfur S (53.4%) and may contain smaller amounts of nickel and cobalt.
It has several forms of presentation, but the most common are in the form of cubes and octahedrons and with twelve sides, all of them can be striated, in addition, they happen to be massive, granular and elongated.
Pyrite stone meaning
The pyrite stone is one of the most famous minerals in the world and behind this stone there are a lot of beliefs and legends. A widespread belief is that the pyrite stone attracts wealth and also protects it. Therefore it is also said that it manages to attract the personal success and balance finances.
Meaning and spiritual properties
The pyrite stone in almost all cultures of the world is a symbol of excellence and prosperity. It is thought to be a magnet that attracts positive energies and attracts good things into your life, including wealth, job opportunities and business opportunities.
Finally, the pyrite stone is believed to give us strength to overcome challenges, eliminate negative thoughts and feelings and works as a shield against envy, the evil eye and black magic.
Difference Between Pyrite and Gold
| Properties and characteristics | Prayed | Pyrite |
|---|---|---|
| Color | bright golden yellow | Pale yellow |
| Mohs hardness | 2.5 to 3 | 6, 6.5 to 7 |
| stripe color | golden yellow | Dark green |
| way of introducing yourself | massive, granular | mainly cubic |
| Changes | does not rust | rusts easily |
| Chemical composition | Ow, native | Iron Sulfide (FeS2) |
| Malleability | Very malleable, it does not break and deform (it can be easily shaped in various ways) | It is very fragile, it breaks easily |
This is the classic example, everyone involved in earth sciences has heard about “fool’s gold”, which means that there are people who confuse the pyrite with gold, and wow, with the naked eye, without a magnifying glass, without a scratcher and without knowing anything about minerals, this can happen to anyone.
However, now you will know that in terms of physical properties gold has hardness (2.5 to 3) which is much less than that of pyrites, so you can even scratch it with your fingernail, also, gold is malleable, so it can bend if you try.
Also, gold has a characteristic bright yellow (golden) color, something that pyrites they dont have it.
Finally, gold does not rust.
Now the pyrites they have hardness (6 to 6.5) that is much greater than that of gold, they break brittle, their color is brassy yellow, and they sometimes turn gray due to oxidization.
And talked about the rust pyrite, when this happens, it is common for ferrihydrite or the formerly known limonite to form as patinas that surround the pyrites.
The habit is also different, because the pyrites they are cubic, octahedral, twelve-sided, elongated and commonly striated.
And remember the pyrites They are not malleable, that is, they will break when you try to “bend” them.
Origin, formation and geological environment
The pyrite It is a mineral that can occur in various geological environments, however, the most common are sedimentary environments associated with the decomposition of organic matter and hydrothermal environments in a wide range of temperatures, in addition, it can form directly from magma crystallization.
Pyrite in sedimentary environment
Conditions include sediments rich in decaying organic material, iron supply, sulfur supply, and all in generally shallow marine oxygen-poor conditions or environment.
Let’s understand a bit, the organic decomposition in these sediments consumes oxygen and releases sulfur that reacts with the existing iron in the environment and forms the pyrites.
For this reason it is common to find this mineral in rocks with a high percentage of organic matter such as shales and siltstones (black and gray shales), slates and phyllites (black and gray, that is, graphitous) and limestones (black and gray).
In addition, it is thanks to this process that fossils of pyrite.
hydrothermal pyrite
The pyrite When it has a hydrothermal origin, it does not represent a mineral that forms at the same temperature, rather, it is a mineral that occurs in hydrothermal environments from low to high temperatures.
Therefore, it is associated with different types of deposits, such as high sulphidation epithermals, volcanogenic massive sulphides (VMS), porphyry copper deposits and skarns.
To define the temperature range and the associated deposit, the minerals that occur together must be seen.
For example, if it occurs in association with argentite, cinnabar, and stibnite, it would be a low-temperature, shallow-depth environment.
But if it occurs in association with cassiterite, magnetite, chalcopyrite, wolframite, molybdenite, it would be in a deep, high-temperature hydrothermal environment.
Furthermore, when the pyrites that have formed in deep conditions are exposed to the surface it is common for them to form gossans or iron cover, which is nothing more than the oxidation of the pyrites.
This oxidation produces a high content of ferrihydrite or limonite.
How to identify the pyrite?
The pyrites They are very common minerals that occur together with several types of minerals, and it is common that they can be confused with gold, chalcopyrite and pyrrhotite.
However, they all have properties that make them different and that is shown in the following diagram that helps you differentiate some gold metallic minerals.
Difference Between Pyrite and Chalcopyrite
There is a characteristic that differentiates the pyrites from most other sulfides because its hardness is quite high compared to other sulfide minerals.
For this reason it is clear that chalcopyrite has a lower Mohs hardness (3.5 to 4) compared to pyrites (6 to 6.5), so you will need a steel scriber to identify the pyrites.
In addition, color is another important factor because the pyrites They appear pale brassy yellow and are sometimes even dark, and chalcopyrite is bright yellow to light greenish.
Also the habit of pyrites it is very different from that of chalcopyrite, for this use a magnifying glass of at least 20 magnification and look at all the mentioned characteristics.
