industrial byproduct (anthropogenic material)
Iron Slag
Iron/Steel Slag (Ferrosilicate Glass)
Hardness: 5-7 (Mohs); Color: Grey, black, or metallic with iridescent patches; Luster: Vitreous to sub-metallic; Crystal Structure: Amorphous (glassy); Specific Gravity: 2.8 - 4.5; often contains vesicles (gas bubbles).
- Hardness
- 5-7 (Mohs)
- Color
- Grey, black, or metallic with iridescent patches
- Luster
- Vitreous to sub-metallic
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Physical properties
Hardness: 5-7 (Mohs); Color: Grey, black, or metallic with iridescent patches; Luster: Vitreous to sub-metallic; Crystal Structure: Amorphous (glassy); Specific Gravity: 2.8 - 4.5; often contains vesicles (gas bubbles).
Formation & geological history
Formed as a byproduct of smelting iron ore or recycling metals. While the minerals involved are ancient, the formation occurs during industrial processes. Commonly found in areas with a history of industrial smelting or railroad beds.
Uses & applications
Used in construction as road base, railroad ballast, asphalt aggregate, and sometimes in fertilizer. Often kept by amateur rockhounds as 'curiosity' specimens.
Geological facts
Slag is often mistaken for meteorites (dubbed 'meteorongs') because of its melted appearance, high density, and occasional magnetic properties. It is a man-made glass-like substance created to remove impurities from melted metal.
Field identification & locations
Field identification: Look for spherical bubbles (vesicles) which are absent in true meteorites. It may have a 'flow' texture or glassy sharp edges when broken. Frequently found near old industrial sites, tracks, or rivers.
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