Anthropogenic (Industrial byproduct)
Ferro-Manganese Slag
Vitreous Silicate Slag
Hardness: 5.5-6.5 (Mohs); Color: Olive green to deep black; Luster: Glassy/Vitreous; Structure: Amorphous (non-crystalline); Cleavage: Conchoidal (shell-like) fracture; Specific Gravity: Approx. 2.8-4.0
- Hardness
- 5
- Color
- Olive green to deep black
- Luster
- Glassy/Vitreous
Identified More anthropogenic (industrial byproduct) →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5.5-6.5 (Mohs); Color: Olive green to deep black; Luster: Glassy/Vitreous; Structure: Amorphous (non-crystalline); Cleavage: Conchoidal (shell-like) fracture; Specific Gravity: Approx. 2.8-4.0
Formation & geological history
Formed as a byproduct of smelting iron or manganese ore. The glassy texture occurs when the molten waste material is cooled rapidly. These are common in historical industrial areas, often dating from the late 19th to early 20th centuries.
Uses & applications
Historically used as railroad ballast or road base. Today, it is popular with rockhounds and collectors for its aesthetic 'pseudo-gemstone' appearance. Occasionally used in unique jewelry or as garden decor.
Geological facts
Slag can often be mistaken for obsidian or moldavite due to its glassy texture, but the presence of air bubbles (vesicles) and its location near historical blast furnaces usually identifies it as industrial waste.
Field identification & locations
Identify in the field by looking for conchoidal fractures, air bubbles, and a glassy surface. They are frequently found near old steel mills, railroads, or riverbanks in industrial regions like Ohio or Pennsylvania.
More like this
Other anthropogenic (industrial byproduct) specimens
Ferrous Slag
Fused calcium-iron silicates (Industrial Slag)
Anthropogenic/Industrial byproduct
Iron Slag
Iron smelting byproduct (Glassy/vesicular silicate)
anthropogenic / industrial byproduct
Iron Slag
Anthropogenic Iron Silicate
industrial byproduct
Anthropogenic Heat Source (Electronic/Industrial Interface)
Thermal IR emission (Electronic infrastructure)
not a rock or mineral
Aluminum Slag
Anthropogenic Aluminum (Al)
mineral
Slag (Industrial Glassy Byproduct)
Anthropogenic silicate byproduct (Slag)
Mineral-like byproduct (often mistaken for igneous rock or meteorite)