Pyrite
Also Fool's gold
Iron sulphide in perfect brass cubes, the stone that struck fire.
- Family
- Pyrite
- Formula
- FeS₂
- Mohs
- 6 to 6.5
- System
- Cubic
Science
Pyrite crystallises as cubes, octahedra and pyritohedra with striated faces; the interlocking cubes of Navajún in La Rioja are the sharpest natural crystals known. Struck against steel it sparks, hence its name from pyr, fire. It oxidises to sulphuric acid, which is why old specimens crumble.
- Mineral
- Pyrite
- Formula
- FeS₂
- Crystal system
- Cubic
- Mohs hardness
- 6 to 6.5
- Specific gravity
- 4.95 to 5.10
- Refractive index
- Opaque
- Lustre
- Metallic
- Colours
- Brass yellow
Composition
FeS₂. Made of Iron, Sulfur, with trace Gold, Nickel, Cobalt responsible for colour.
Origin
- SpainNavajún, perfect cubes
- PeruHuanzalá
- ItalyElba
- United States
- Russia
- China
Filled dots are primary sources
Rarity
The most common sulphide mineral. Navajún cubes, which grow in marl as if machined, are prized regardless.
- 1 Abundant
- 2 Common
- 3 Uncommon
- 4 Rare
- 5 Exceptional
Hardness
Pyrite sits at 6 to 6.5 on the Mohs scale. Glass and a knife blade are about as hard; it wears well with care.
Energy
Associations from crystal-healing tradition, recorded here as folklore. They are not medical claims.
Chakras
- Solar Plexus
Element
- Fire
Zodiac
- Leo
Planets
- Sun
- Mars
Properties
- Wealth
- Willpower
- Shielding
- Vitality
Lore
Wheellock pistols of the 1500s fired by spinning a steel wheel against pyrite. Incas polished it into mirrors; Greeks used it as jewellery. Its fool's-gold nickname is unfair: pyrite ore often carries real gold in its lattice.
Modern practice treats it as a shield and a magnet for money, following the colour.
- MarcasiteSame formula, orthorhombic; 'marcasite' jewellery is actually pyrite.
- Pyrite diseaseSpecimens can decay in humid air into acid and powder.