Pyrite
Iron Sulfide (Pyrite) · Mineral Specimen / Industrial Mineral / Semi-Precious Gemstone
Crystal System
Cubic; common habits include cubic, octahedral, and pyritohedral forms, as well as massive or granular aggregates.
Mineral Group
Sulfides
Chemical Formula
FeS2 (Iron Disulfide)
Formation Process
Primarily hydrothermal veins and contact metamorphic deposits; also forms in sedimentary rocks via biogenic reduction of sulfate.
About This Crystal
A brassy-yellow mineral with a strong metallic luster. Often occurs as well-defined cubes or pyritohedrons. It is opaque with a brittle texture and may show iridescent tarnishing (peacock colors) when oxidized.
Physical Characteristics
Color: Pale brass-yellow; Streak: Greenish-black to brownish-black; Hardness: 6.0–6.5; Specific Gravity: 4.9–5.2; Fracture: Conchoidal to uneven; Tenacity: Brittle.
Optical Properties
Opaque with metallic luster; strongly reflective. Under reflected light microscopy, it appears creamy white with a slight yellow tint. Not applicable for RI or birefringence due to opacity.
Hardness & Durability
Origin Region
Globally distributed; notable sources include Spain (Rio Tinto), Peru (Huánuco), Italy (Elba), and the USA (Colorado and Arizona).
Hardness & Durability
Mohs hardness of 6–6.5. Relatively hard for a sulfide but brittle; susceptible to "pyrite disease" (oxidation and decomposition) in high humidity.
Care & Maintenance
Keep dry to prevent oxidation (sulfuric acid production). Clean with a soft, dry cloth; avoid water, ultrasonic cleaners, and harsh chemicals. Store in a low-humidity environment.
Rarity & Value
Very common; generally inexpensive. Value increases for large, perfectly formed cubic crystals or unique clusters. Often treated with a light oil or lacquer to prevent tarnishing.
Special Characteristics
Striated crystal faces (parallel to cubic edges); sparks when struck against steel (hence the name from the Greek 'pyr' for fire); can show minor gold inclusions.
Lore & History
Historically known as 'Fool's Gold' due to its resemblance to precious metals. Used by ancient Greeks and Romans to strike fire. Traditionally associated with the Solar Plexus chakra, symbolizing willpower, protection, and logic.