Pyrite

Iron Sulfide FeS2

Pyrite is a compound of iron and sulfur, iron sulfide FeS2. Depending upon the conditions under which it forms this mineral can form crystals of different shapes. The crystals are isometric, meaning that they have equal faces. Cubes are common. Octahedral and dodecahedral shapes are also seen frequently.

The name comes from the Greek word for fire “pyr”, literally fire rock. This is because it sparks when struck against iron.

Because of its high sulfur content pyrite is used in making sulfuric acid and sulfur dioxide.

It can be an agent of fossilization creating beautiful fossils, commonly ammonites and brachiopods.

Pyrite suns are found in slate seams of coal mines. These "suns" are flat disc shapes with a radial pattern. No one knows exactly how they are formed. There are two prevalent theories; one is that they are pyritized fossils of an unknown animal. Another is that they are pyrite crystals spread out in the thin seams of slate where they are found.

In the gold rush era, many people thought they had discovered gold only to realize it was pyrite, which is where it gets its nickname fools gold.

The hardness of this mineral is about 6-6.5 on the Mohs scale. It has a metallic luster and normally has a yellow brassy color.

pyrite cube
Pyrite Cube

Of the sulfide minerals pyrite is the most common. It is usually found in quartz veins with other sulfides and oxides.

Mining operations sometimes leave large amounts of pyrite in tailings. This causes environmental damage because it reacts with oxygen and water to form sulfuric acid.

Mineral Properties
Chemical formula: Iron Sulfide FeS2
Color(s): gold-yellow
Streak: greenish black
Luster: metallic
Transparency: opaque
Crystal system: cubic
Specific Gravity: 4.8-5
Hardness (Mohs): 6-6.5
Cleavage: indistinct
Fracture: conchoidal
Uses: used in making sulfuric acid and sulfur dioxide
Location: Rio Tinto, Spain; Quiruvila, Peru; Ontario, Canada; Elba, Italy; Llallagua, Bolivia; In the U.S.A. Utah, Colorado

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