mineral

Blue slag glass / industrial smelter slag

Man-made iron-rich silicate slag; composition variable, commonly Fe–Ca–Mg–Al silicates with glassy phases

AI-generated identification · may be incorrect

Dark blue-black, irregular and vesicular, with a glassy to dull luster and scattered metallic-looking surfaces; hardness typically about 5–6 Mohs, no consistent cleavage, and variable density. The rounded shape and bubbly texture suggest a processed industrial specimen rather than a natural crystal.

Identified August 20, 2026More mineral →

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Physical properties

Formation & geological history

Produced as a byproduct of metal smelting or furnace operations when molten silicate waste cools rapidly; it is anthropogenic and has no geological age. Blue coloration may result from iron, copper, cobalt, or other metal-bearing components.

Uses & applications

Collected as slag or “industrialite,” and occasionally used decoratively; it has little conventional construction or jewelry value unless unusually attractive or historically significant.

Geological facts

Slag can resemble obsidian, basalt, or meteorites but commonly contains bubbles, flow banding, unmelted grains, or rusty metal inclusions. A magnet may attract iron-rich pieces, though not all slag is magnetic.

Field identification & locations

Identify by vesicles, flow textures, heterogeneous glass, and possible metal flecks; natural volcanic glass is generally more uniform and sharp-fracturing. Common near historic furnaces, mines, railways, and smelting districts.