Iron Slag (Industrial By-product)
Anthropogenic Silicate/Oxide Mass · Industrial By-product (often mistaken for Meteorite)
Crystal System
Amorphous / Non-crystalline (Glassy to Microcrystalline)
Mineral Group
Technofossil / Silicate-Oxide Mix
Chemical Formula
Variable; primarily FeO, SiO2, CaO, Al2O3, with trace sulfur and manganese.
Formation Process
Anthropogenic; formed by the rapid cooling of molten impurities separated during the smelting of iron ore or metal refining.
About This Crystal
A dense, dark, irregular mass featuring a vesicular (pitted) surface. It displays a dull to sub-metallic luster on the exterior with patches of orange-brown oxidation (rust) and occasional white calcification or adhering soil.
Physical Characteristics
Color: Gunmetal gray to black with iron-oxide staining; Streak: Gray or reddish-brown; Cleavage: None; Fracture: Conchoidal to uneven; Specific Gravity: High (approx 2.8 - 4.5); Fluorescence: None.
Optical Properties
Opaque; Non-refractive (amorphous); No pleochroism or dispersion; Luster varies from earthy to glassy depending on silica content.
Hardness & Durability
Origin Region
Found worldwide in areas of historical iron smelting, former glassworks, or industrial landfill sites.
Hardness & Durability
Mohs Hardness: 5.0 - 7.0 (variable); Brittle toughness; Generally stable but prone to continued oxidation if iron content is high.
Care & Maintenance
Keep dry to prevent further rusting of iron components; clean with a soft brush; avoid acids which may react with carbonate or metallic inclusions.
Rarity & Value
Common; Minimal monetary value. Often sold as a curiosity or incorrectly as a 'meteorite'. Value is primarily historical if found at an archaeological smelting site.
Special Characteristics
Vesicular texture (gas bubbles), which is a key indicator that it is slag rather than a meteorite (meteorites are rarely vesicular). It is often strongly magnetic.
Lore & History
Historically significant for tracing ancient industrial techniques and trade routes. In metaphysical circles, it is sometimes used as a 'grounding' stone due to its iron content, though it lacks the traditional lore of natural gemstones.