mineral

Banded Agate (Onyx Variety)

Silicon Dioxide (SiO2) - Cryptocrystalline Quartz

Hardness: 6.5–7 on Mohs scale; Color: Alternating white and brown/black bands; Luster: Vitreous to waxy; Crystal structure: Trigonal (microscopic); Cleavage: None (Conchoidal fracture); Specific gravity: 2.60–2.65

Hardness: 6
Color: Alternating white and brown/black bands
Luster: Vitreous to waxy

Identified March 15, 2026More mineral →

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Physical properties

Formation & geological history

Formed in volcanic and metamorphic environments where silica-rich groundwater deposits layers over time within gas cavities (vesicles). These layered deposits create the distinct banding patterns seen in the inlay.

Uses & applications

Used primarily in jewelry, ornamental carvings, intaglios, and high-end fashion accessories. This specific item is a jewelry inlay for a gold-toned hinge bracelet.

Geological facts

Banded agate has been used by humans since Neolithic times for amulets and tools. The parallel white and dark banding shown here is often commercially referred to as 'Sardonyx' or 'Onyx' depending on the specific color of the darker layers.

Field identification & locations

Identify by looking for distinct, parallel, opaque and translucent bands and a high degree of polish. For collectors, authenticity is checked by hardness (it should not be easily scratched by steel) and lack of surface bubbles common in plastic imitations.

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