mineral

Aluminum Slag

Anthropogenic Aluminum (Al)

Hardness: 2.5-3 (Mohs). Color: Silvery-gray to dull white. Luster: Metallic. Crystal structure: Face-centered cubic (rarely visible in melt). Specific gravity: 2.7. Very lightweight for its size.

Hardness: 2
Color: Silvery-gray to dull white
Luster: Metallic

Identified May 10, 2026More mineral →

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Physical properties

Hardness: 2.5-3 (Mohs). Color: Silvery-gray to dull white. Luster: Metallic. Crystal structure: Face-centered cubic (rarely visible in melt). Specific gravity: 2.7. Very lightweight for its size.

Formation & geological history

Formed as a byproduct of aluminum smelting or, more commonly, from melted aluminum cans/refuse in a campfire or industrial waste fire. It is anthropogenic (man-made) rather than naturally occurring.

Uses & applications

Generally used for recycling or as a common find for beachcombers and metal detectorists. It has no primary industrial use in its slag form except as scrap metal.

Geological facts

Many people mistake aluminum slag for silver or meteorites because of its metallic shine and unusual shape. However, its low density (light weight) is a dead giveaway that it is aluminum.

Field identification & locations

Identify by its light weight relative to its size (low density), soft surface that can be scratched by a knife, and the presence of gas bubbles (vesicles) on the surface indicating it was once molten. Found near old campsites, industrial zones, or beach fire pits.