mineraloid
Cullet Glass (Slag Glass)
Amorphous Silicon Dioxide (Industrial Byproduct)
Hardness: 5.5-6.0 Mohs; Color: Aquamarine/Blue-green; Luster: Vitreous; Structure: Amorphous (no crystal structure); Cleavage: None (conchoidal fracture); Specific Gravity: 2.4-2.8
- Hardness
- 5
- Color
- Aquamarine/Blue-green
- Luster
- Vitreous
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Physical properties
Hardness: 5.5-6.0 Mohs; Color: Aquamarine/Blue-green; Luster: Vitreous; Structure: Amorphous (no crystal structure); Cleavage: None (conchoidal fracture); Specific Gravity: 2.4-2.8
Formation & geological history
This is a man-made industrial byproduct formed when glass-making furnaces are cleaned or when molten glass is discarded and rapidly cooled. It is not a naturally occurring geological specimen.
Uses & applications
Used as garden decoration, landscape aggregate, aquarium gravel, or melted down for recycling into new glass products (cullet). Large pieces are popular with collectors of curiosity items.
Geological facts
While often mistaken for obsidian or large gemstone crystals, the bubble inclusions seen in the material confirm its industrial origin. It is physically similar to natural volcanic obsidian but comes in colors not found in nature.
Field identification & locations
Identify in the field by looking for air bubbles (vesicles), conchoidal (shell-like) fracture patterns, and extremely vibrant colors. It is often found near old glass factories or dumped in riverbeds near industrial zones.
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