Pyrite
Iron Sulfide (Pyrite) · Mineral Specimen / Industrial Mineral
Crystal System
Cubic (Isometric) system; typically occurs as cubes, pyritohedrons, or octahedrons. This specimen shows a drusy to massive habit with various interlocking crystalline faces.
Mineral Group
Sulfides
Chemical Formula
FeS2 (Iron Disulfide), occasionally containing trace amounts of nickel, cobalt, arsenic, and gold.
Formation Process
Primarily Hydrothermal or Sedimentary. It forms through the precipitation of iron and sulfur in oxygen-poor environments, often associated with volcanic activity or organic decomposition in sedimentary layers.
About This Crystal
A brassy-yellow metallic mineral with a bright luster. This specimen exhibits a granular, crystalline surface (drusy) that catches light across multiple tiny faces. It appears opaque with a pale brassy-yellow color and a metallic to sub-metallic luster.
Physical Characteristics
Color: Brass-yellow; Streak: Greenish-black to brownish-black; Cleavage: Indistinct; Fracture: Conchoidal to uneven; Specific Gravity: 4.9–5.2; Tenacity: Brittle; Notable for its metallic 'fool's gold' appearance.
Optical Properties
Opaque (no refractive index in the visible range); Metallic luster; Non-pleochroic; Singly refractive in theory but often shows anomalous anisotropy due to crystal strain.
Hardness & Durability
Origin Region
Found globally; notable sources include Spain (Rio Tinto), Peru (Huanzala), Italy (Elba), and the USA. It occurs in varied geological environments including sedimentary rocks, hydrothermal veins, and metamorphic deposits.
Hardness & Durability
Mohs Hardness: 6–6.5. It is relatively hard and brittle compared to real gold (which is 2.5–3). It can scratch copper but can be scratched by a steel file.
Care & Maintenance
Keep dry; Pyrite can oxidize ('pyrite decay') in high humidity, turning into iron sulfates. Clean with a soft, dry cloth or brush. Avoid ultrasonic cleaners and water immersion. Store in a low-humidity environment.
Rarity & Value
Common. Generally inexpensive for small to medium specimens. Value increases for large, perfectly formed cubes or specimens on host matrices. Rarely treated, though sometimes cleaned with light acids.
Special Characteristics
Known as 'Fool's Gold' due to its color. It is paramagnetic and can produce sparks when struck against steel (giving it the name 'pyrite' from the Greek 'pyr' for fire).
Lore & History
Historically used by the Greeks and Romans to strike fire. In traditional lore, it is associated with the Solar Plexus chakra and believed to represent wealth, abundance, and protection. It was also used in prehistoric burial ornaments and mirrors.