mineraloid (anthropogenic byproduct)
Iron Slag
Ferrous Slag (Industrial Byproduct)
Hardness: 5-7 (Mohs); Color: Dark brown, black, to rusty orange; Luster: Dull to sub-metallic or glassy; Structure: Amorphous/Vesicular; Specific Gravity: 2.8-4.0. Features bubbles (vacuoles) and smooth flow textures.
- Hardness
- 5-7 (Mohs)
- Color
- Dark brown, black, to rusty orange
- Luster
- Dull to sub-metallic or glassy
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Physical properties
Hardness: 5-7 (Mohs); Color: Dark brown, black, to rusty orange; Luster: Dull to sub-metallic or glassy; Structure: Amorphous/Vesicular; Specific Gravity: 2.8-4.0. Features bubbles (vacuoles) and smooth flow textures.
Formation & geological history
Formed as a byproduct of the iron smelting process where impurities (gangue) are separated from molten metal. This specimen likely dates from the industrial era and formed by rapid cooling of molten waste.
Uses & applications
Used in construction as road base, railroad ballast, and as an additive in cement manufacturing. Historically used as a cheap building material or discarded as waste.
Geological facts
Slag is often mistaken for meteorites due to its dark color and pitted surface (vesicles), but its flow-like textures and internal glassiness are distinct features of industrial cooling.
Field identification & locations
Identify by the presence of vesicles (gas bubbles), glassy textures on fresh breaks, and proximity to historic industrial sites. It is often non-magnetic or only weakly magnetic compared to magnetite or meteorites.
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