Pyrite Sun
Marcasite var. Pyrite Sun (Pyrite Radial Aggregates) · Mineral Specimen
Crystal System
Orthorhombic (for Marcasite) or Isometric (for Pyrite), typically forming radiating, disk-like aggregates known as pyrite suns or pyrite dollars.
Mineral Group
Sulfides
Chemical Formula
FeS2
Formation Process
Sedimentary/Diagenetic formation occurring in coal seams and carbonaceous shales, where iron and sulfur precipitate in reducing environments under low temperatures and pressures.
About This Crystal
The specimen appears as a flattened, radiating, disk-like mineral aggregate, commonly referred to as a pyrite sun or pyrite dollar. It exhibits a metallic luster, a dark brownish-gray to brassy color due to oxidation and tarnish, and a rough, botryoidal to radiating crystalline surface texture.
Physical Characteristics
Color ranges from brass-yellow to dark metallic gray/brown due to surface tarnish. Streak is greenish-black to brownish-black. Cleavage is indistinct, fracture is uneven to conchoidal, specific gravity is approximately 4.8 to 5.0, and tenacity is brittle.
Optical Properties
Opaque with a strong metallic luster. Does not exhibit refraction, pleochroism, or advanced optical phenomena due to its opaque metallic nature.
Hardness & Durability
Origin Region
Illinois, USA (specifically the coal mines around Sparta and Coulterville), and various locations worldwide in sedimentary shale formations.
Hardness & Durability
Mohs hardness of 6 to 6.5. It is relatively brittle and can flake or crumble if handled roughly. Sensitive to moisture, which can cause oxidation and degradation (rusting/sulfate decay).
Care & Maintenance
Clean with a dry brush. Avoid water and high humidity to prevent oxidation and sulfuric acid breakdown (pyrite decay). Store in a dry environment with low humidity.
Rarity & Value
Uncommon to rare depending on the size and perfection of the sun formation. Value is determined by size, completeness, and lack of heavy oxidation/crumbling. Price ranges from moderate to high for exceptionally large or well-formed specimens.
Special Characteristics
Notable for its unique radial, sunburst crystallization habit found exclusively within organic-rich shale and coal layers.
Lore & History
Historically used by collectors as a fascinating geological curiosity. In modern metaphysical practices, pyrite suns are believed to represent vitality, energy, and the grounding of high-frequency energy into the physical body, though these are traditional beliefs and not scientific claims.