Pyrite gold cubes

Pyrite in golden cubes, known as fool's gold, is an iron sulfide mineral with striking cubic form.

About this subject

Pyrite, an iron sulfide (FeS2), is one of the most common and recognizable minerals in the Earth's crust. Its golden color and metallic luster often lead to confusion with real gold, hence the nickname "fool's gold." However, pyrite is much harder (6-6.5 on the Mohs scale) and less malleable than gold. Perfect cubic crystals form under hydrothermal conditions, typically in quartz veins or sedimentary rocks, and can reach several centimeters in size. Pyrite is not just fake gold; it has industrial importance in the production of sulfuric acid and, in some deposits, contains traces of real gold, making it economically valuable. Contrary to popular belief, pyrite is not radioactive, though it may be associated with radioactive minerals. Collectors prize specimens with well-defined cubes and smooth faces, such as those from Navajún, Spain, considered the finest in the world.

Frequently Asked Questions

What is the difference between pyrite and gold?

Pyrite is harder, lighter, and brittle, while gold is malleable and much denser. A simple test: gold leaves a yellow streak on porcelain, pyrite leaves a black streak.

Where are the best cubic pyrite crystals found?

The Navajún mine in La Rioja, Spain, is famous for producing the largest and most perfect pyrite cubes, sometimes up to 15 cm on edge.

Does pyrite have any practical uses?

Yes, it is the main source of sulfuric acid, used in batteries, fertilizers, and petroleum refining. It is also mined for its gold content in some deposits.