mineraloid (man-made)
Glass Nugget (Tumbled Glass)
Amorphous Silicon Dioxide (SiO2) with additives
Hardness: 5-6 Mohs. Color: Cobalt blue (transparent). Luster: Vitreous/Glassy. Structure: Amorphous (non-crystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.4-2.8.
- Hardness
- 5-6 Mohs
- Color
- Cobalt blue (transparent)
- Luster
- Vitreous/Glassy
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Physical properties
Hardness: 5-6 Mohs. Color: Cobalt blue (transparent). Luster: Vitreous/Glassy. Structure: Amorphous (non-crystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.4-2.8.
Formation & geological history
Manufactured through industrial heating of silica sand, soda ash, and limestone at temperatures exceeding 1700 degrees Celsius, followed by mechanical shaping and tumbling to create a smooth, rounded finish.
Uses & applications
Primarily used for decorative purposes in vases, aquariums, mosaics, and landscape design. Sometimes used in low-cost craft jewelry or as game pieces.
Geological facts
While frequently mistaken for sea glass or natural stones like obsidian, these are mass-produced. Similar chemical compositions are found in natural volcanic glass, but the uniform shape and specific cobalt coloring are hallmarks of industrial production.
Field identification & locations
Identify by looking for air bubbles trapped inside (not typical in natural stones), perfectly symmetrical shapes, and a lack of crystalline structure. These are found in craft stores and mass-market home decor aisles rather than natural geological sites.
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