Mineral description (Anthropogenic material)
Slag (Industrial Byproduct)
Artificial silicate/iron byproduct
Hardness: 5.5-7 (Mohs scale), Color: Black/dark grey, Luster: Vitreous to metallic, Structure: Amorphous/glassy, often containing vesicles (gas bubbles).
- Hardness
- 5
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Physical properties
Hardness: 5.5-7 (Mohs scale), Color: Black/dark grey, Luster: Vitreous to metallic, Structure: Amorphous/glassy, often containing vesicles (gas bubbles).
Formation & geological history
Formed as a byproduct of smelting ores (iron, copper, or lead) or coal combustion. It behaves like an igneous rock in that it is cooled molten material, but it is man-made.
Uses & applications
Used as railroad ballast, road base material, in concrete aggregate, and occasionally ground up for roofing granules or used as an abrasive.
Geological facts
Slag is often mistaken for meteorites due to its dark, heavy appearance and holes, but those holes (vesicles) are actually proof it is earthly volcanic or industrial material.
Field identification & locations
Identify in the field by looking for gas bubbles (vesicles), a glassy/scoriaceous texture, and presence near historical industrial sites or railways.
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