Mineral-like byproduct (often mistaken for igneous rock or meteorite)
Slag (Industrial Glassy Byproduct)
Anthropogenic silicate byproduct (Slag)
Hardness: 5-6 (Mohs); Color: Dark brown to black with glassy surface; Luster: Vitreous to dull; Structure: Amorphous/vesicular (full of air bubbles); Cleavage: Conchoidal (obsidian-like fracture).
- Hardness
- 5-6 (Mohs)
- Color
- Dark brown to black with glassy surface
- Luster
- Vitreous to dull
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark brown to black with glassy surface; Luster: Vitreous to dull; Structure: Amorphous/vesicular (full of air bubbles); Cleavage: Conchoidal (obsidian-like fracture).
Formation & geological history
Formed as a byproduct of smelting ores (iron, steel, copper) where impurities are separated from the molten metal. The 'bubbles' or vesicles were formed by escaping gases as the material cooled rapidly.
Uses & applications
Historically used as road ballast, railroad fill, or aggregate for concrete. Occasionally used in jewelry as 'Detroit Agate' or 'Leland Blue' if the colors are unique.
Geological facts
Slag is the most common material mistaken for meteorites (often called 'meteor-wrongs') due to its burnt appearance, high weight compared to common rocks, and occasional magnetic properties if iron-rich.
Field identification & locations
Identify in the field by looking for spherical gas bubbles (vesicles), which are rare in meteorites but common in slag. Often found near old railroad tracks, former industrial sites, or in creek beds in industrial regions.
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Industrial byproduct (often confused with igneous rocks or meteorites)
Slag (Industrial Byproduct)
Artificial silicate/iron byproduct
Mineral description (Anthropogenic material)
Iron Slag
Anthropogenic Iron Silicate
industrial byproduct
Slag (Industrial Glass/Metal)
Ferrous slag or Glassy silicate byproduct
Antropogenic rock (Man-made)
Slag
Anthropogenic Iron Silicate Glass
mineral
Slag
Ferrous Slag (Amorphous calcium-magnesium-aluminum silicates)
igneous (artificial/anthropogenic)