mineraloid (anthropogenic)
Slag (Industrial Glass)
Artificial Vitreous Silicate
Hardness: 5.5-7.0 (Mohs scale), Color: Black to dark brown with iridescent sheen, Luster: Vitreous to sub-metallic, Structure: Amorphous (non-crystalline), often contains vesicles (bubbles) and conchoidal fractures.
- Hardness
- 5
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Physical properties
Hardness: 5.5-7.0 (Mohs scale), Color: Black to dark brown with iridescent sheen, Luster: Vitreous to sub-metallic, Structure: Amorphous (non-crystalline), often contains vesicles (bubbles) and conchoidal fractures.
Formation & geological history
Formed as a byproduct of smelting ores (such as iron or copper) where impurities are separated from the molten metal. The liquid waste cools rapidly to form a glass-like or stony material.
Uses & applications
Commonly used as high-quality road base, railroad ballast, roofing granules, and as a component in cement and concrete manufacturing. Some colorful varieties are used for jewelry.
Geological facts
Slag is often mistaken for meteorites or volcanic obsidian due to its dark color and glassy texture. Large deposits can often be found near historic iron furnaces or industrial centers.
Field identification & locations
Identify by looking for small bubble holes (vesicles) on the surface, a glassy texture when broken, and flow lines. It is frequently found in urban or industrial areas rather than natural geological outcrops.
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