Slag (Industrial)

Physical Properties

Hardness varies (generally 5-6), color is dark grey, brown, or black, often with a rusty appearance, dull to slightly shiny luster, amorphous structure, lacks cleavage, high specific gravity if iron-rich, often vesicular (contains holes or pores).

Formation & Geological History

Formed as a by-product of smelting ore to purify metals. It is the glassy mass left over after the desired metal has been separated from its raw ore.

Uses & Applications

Used in construction, as aggregate in concrete, road base material, and sometimes in fertilizer.

Geological Facts

Often mistaken for meteorites due to its dark color, high density, and melted appearance (vesicles). It is a common 'meteorwrong'.

Field Identification & Locations

Identify by the presence of vesicles (gas bubbles), irregular shape, lack of fusion crust typical of meteorites, and context of where it was found (often near old industrial sites or railroad tracks). Sometimes weakly magnetic.

Identified on: 4/26/2026

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