mineral
Banded Agate Coaster
Silicon Dioxide (SiO2) - Variety Agate / Chalcedony
AI-generated identification · may be incorrectHardness: 6.5-7 Mohs. Color: Blue-grey, white, tan, and cream with concentric banding. Luster: Vitreous to waxy. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.58-2.64.
- Hardness
- 6
- Color
- Blue-grey, white, tan, and cream with concentric banding
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 Mohs. Color: Blue-grey, white, tan, and cream with concentric banding. Luster: Vitreous to waxy. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.58-2.64.
Formation & geological history
Formed as silica-rich groundwater fills gas cavities (vesicles) in volcanic rock or holes in sedimentary rocks. Over time, rhythmic deposition of minerals creates the distinctive banding. These processed pieces often come from deposits in Brazil or Uruguay.
Uses & applications
Used for interior decoration, home goods (coasters), jewelry cabochons, and metaphysical collecting. Its hardness makes it ideal for functional household items.
Geological facts
Agate was named by the Greek philosopher Theophrastus, who discovered the stone along the shoreline of the Achates River in Sicily. This specific specimen has been cut and polished into a circular slab for use as a drink coaster.
Field identification & locations
Identify by its waxy luster and distinctive banding which remains visible even after polishing. In the field, look for nodules with a rough, weathered rind that reveals colorful interiors when broken or sliced. Agates are common in basaltic volcanic fields worldwide.
