mineral

Banded Agate Coaster

Silicon Dioxide (SiO2) - Variety Agate / Chalcedony

AI-generated identification · may be incorrect

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.

Hardness: 6
Color: Blue-grey, white, tan, and cream with concentric banding
Luster: Vitreous to waxy

Identified July 10, 2026More mineral →

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Physical properties

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.