Pyrite

Pyrite, also called iron pyrite or Fool's Gold, is a common mineral made of iron and sulfur, with the chemical formula FeS₂. It is the most common sulfide mineral found in nature.

What makes pyrite special is its bright, shiny look and pale yellow color, which looks a lot like gold. Because of this, people often called it Fool's Gold. Other old names for pyrite include brass, brazzle, and brazil, especially when found in coal.

The word pyrite comes from Greek words for “stone that strikes fire,” because when pyrite is hit against steel, it can make sparks. Ancient people noticed this special property long ago. Today, pyrite is often found in rocks such as quartz veins, sedimentary and metamorphic rocks, and even in some fossils. Sometimes, tiny bits of real gold can be found with pyrite, hidden inside the mineral.

Uses

Pyrite was used long ago to help start fires and early guns by making sparks. The Kaurna people of South Australia used it with flintstone and special tinder to start fires.

Today, pyrite is used to make sulfur dioxide. This helps make paper and sulfuric acid. It is also used in batteries and solar panels. Because it looks like gold, pyrite is sometimes used in jewelry and decorations, especially with silver. Many people collect pyrite, and some of the best samples come from Spain.

Research

In July 2020, scientists found that electricity could change pyrite so it could attract magnets. This could help make things like solar cells or devices that store data.

Researchers in Ireland showed that pyrite could be made very thin by using liquids. They used these thin pieces of pyrite with carbon tubes in batteries, and they worked very well. Later, in 2021, they made even better thin pieces of pyrite that worked even better in batteries.

Formal oxidation states for pyrite, marcasite, molybdenite and arsenopyrite

In classic chemistry, pyrite and marcasite are described as Fe²⁺[S₂]²⁻. This shows that the sulfur atoms in pyrite are paired together. These pairs are similar to units from hydrogen disulfide, H₂S₂, so pyrite could be called iron persulfide instead of iron disulfide. Molybdenite, MoS₂, has single sulfide S²⁻ centers, and the molybdenum has a charge of Mo⁴⁺. The mineral arsenopyrite has the formula FeAsS. While pyrite has [S₂]²⁻ units, arsenopyrite has [AsS]³⁻ units. Looking at these charges, arsenopyrite would be described as Fe³⁺AsS³⁻.

Crystallography

Iron-pyrite, with the chemical formula FeS₂, has a special cubic shape that scientists studied using special light called X-ray diffraction. It is part of a group called _Pa_3 and has a specific pattern known as C2.

In this shape, iron atoms form a cube pattern, and sulfur atoms fit into this pattern. The iron atoms connect to six sulfur atoms, making a stretched cube shape. The sulfur atoms also connect in pairs. This structure helps scientists learn about other materials with similar patterns.

Crystal habit

Pyrite often grows in cube shapes. Sometimes, these cubes grow close together to make small, round clusters that look like raspberries, called framboids. It can also grow in thin threads or T-shaped crystals. Pyrite can form shapes that look like a twelve-sided figure called a dodecahedron. Long ago, people in Europe made similar shapes for their art.

Varieties

There are several minerals similar to pyrite, including vaesite, hauerite, and sperrylite. These minerals look much like pyrite.

Another type is called bravoite, which contains nickel and cobalt. Bravoite is not an official mineral and is named after a scientist from Peru named Jose J. Bravo.

Distinguishing similar minerals

Pyrite looks like gold but you can tell them apart. Pyrite breaks easily and has uneven or shell-like pieces. Gold bends and does not break. Gold pieces are usually irregular, but pyrite often forms cubes or crystals with sharp faces. You might also see lines on pyrite’s surface.

Another mineral, chalcopyrite, is a brighter yellow and turns greenish when wet. Arsenopyrite is silver white and stays the same color when wet, unlike pyrite.

Hazards

Iron pyrite can change when it meets air and water. It breaks down and can make the area around it more acidic. This is a problem in places where coal is mined.

When pyrite mixes with dust, it can cause explosions in mines. Miners spray limestone dust to keep things safe.

Buildings made with stone or concrete that contains pyrite can have problems. As the pyrite changes, it can damage the building materials and make them break apart over time.

Occurrence

Pyrite is the most common sulfide mineral. You can find it in many kinds of rocks, such as igneous, metamorphic, and sedimentary rocks. It is usually a small part of these rocks but can sometimes form bigger pieces. Pyrite may be part of the original sediment or form later as the rock changes.

People have found pyrite in places like Virginia in the U.S. and in large amounts in Rio Tinto, Spain, as well as in other locations around the world.

Cultural beliefs

In Thai culture, especially in the south, pyrite is called Khao tok Phra Ruang, Khao khon bat Phra Ruang, or Phet na tang and Hin na tang. People think it is a special item that can help keep away bad things and protect against harmful forces.