industrial byproduct
Slag
Glassy silicate byproduct (anthropogenic material)
Hardness: 5-7 (variable), Color: Black with metallic luster or reddish-brown oxides, Luster: Vitreous to sub-metallic, Structure: Amorphous (non-crystalline) to vesicular, Specific Gravity: 2.5-4.5
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Physical properties
Hardness: 5-7 (variable), Color: Black with metallic luster or reddish-brown oxides, Luster: Vitreous to sub-metallic, Structure: Amorphous (non-crystalline) to vesicular, Specific Gravity: 2.5-4.5
Formation & geological history
Formed as a byproduct of smelting ores (iron, steel, or copper) to separate metal from impurities. It is a man-made geological material usually found in industrial waste areas or roadbeds.
Uses & applications
Used as road base, railroad ballast, raw material for cement production, and as an abrasive for sandblasting. Some samples are collected for their unique glassy appearance.
Geological facts
Slag is often mistaken for meteorites or volcanic rock (like scoria) due to its holes (vesicles) and dark color, but its discovery near historic industrial sites often reveals its true nature.
Field identification & locations
Identify by the presence of bubble-like holes (vesicles), glassy texture, and high density. Often found near railroads, old steel mills, or recycled into pavement.
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