Mineral description (Anthropogenic material)

Slag (Industrial Byproduct)

Artificial silicate/iron byproduct

AI-generated identification · may be incorrect

Hardness: 5.5-7 (Mohs scale), Color: Black/dark grey, Luster: Vitreous to metallic, Structure: Amorphous/glassy, often containing vesicles (gas bubbles).

Hardness: 5

Identified April 2, 2026More mineral description (anthropogenic material) →

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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.