Iron Pyrite Nodules or Boji Stone
Pyrite / Marcasite / Limonite Pseudomorph · Mineral Specimen
Crystal System
Cubic (Pyrite) with botryoidal or spherical habit, often forming as spherical nodules through radial crystallization.
Mineral Group
Sulfoxides / Sulfides group
Chemical Formula
FeS2 (often weathered to FeO(OH)·nH2O)
Formation Process
Sedimentary or Low-Temperature Hydrothermal. Forms when iron and sulfur react in organic-rich reducing environments, such as marine shales or clay layers, often growing outward radially from a central nucleus.
About This Crystal
The specimen appears as a small, roughly spherical, dark brown to rust-colored nodule resting in the palm of a hand. The surface is heavily weathered, showing rough textures with patches of lighter oxidation crust and iron-oxide staining (limonite/goethite), characteristic of weathered iron sulfide concretions.
Physical Characteristics
Color: Dark brownish-black to rusty brown; Streak: Dark greenish-black to brownish-black (if unweathered, though weathered surfaces yield a brownish-yellow limonite streak); Cleavage: Indistinct or none; Fracture: Uneven to conchoidal; Specific Gravity: Approx 4.8 - 5.0 for fresh pyrite, lower if heavily oxidized; Tenacity: Brittle.
Optical Properties
Opaque with a metallic to sub-metallic luster on fresh surfaces, though heavily weathered exterior surfaces appear dull and earthy.
Hardness & Durability
Origin Region
Found globally; notable pyrite and marcasite nodule locations include USA (Kansas, Illinois), Peru, and China. Often recovered from sedimentary shale and clay formations.
Hardness & Durability
Mohs hardness ranges from 6 to 6.5 for fresh pyrite, but weathered outer crusts of limonite/goethite can be softer (around 4 to 5). Brittle and susceptible to breaking upon heavy impact.
Care & Maintenance
Keep dry. Because iron sulfide nodules can contain moisture and sulfur, exposure to high humidity can lead to 'pyrite disease' (oxidation into sulfuric acid and iron oxides), causing the specimen to crumble or develop a white powdery residue. Store in a dry environment and avoid water cleaning.
Rarity & Value
Common. Pyrite nodules and oxidized spheres are widely accessible and affordable mineral specimens, primarily valued by collectors of odd crystal habits and sedimentary concretions.
Special Characteristics
Forms as natural spherical or discoidal concretions, frequently mistaken for ancient artifacts or meteorites due to their spherical shape and heavy weight.
Lore & History
Often marketed under trade names like 'Boji Stones' or 'Shaman Stones' in metaphysical communities. Believed by practitioners to provide grounding, energetic protection, and balance. Historically, iron sulfide nodules were used by ancient peoples as strike-a-lights to create sparks for starting fires.