Blue Onyx (Dyed Agate)

Physical Properties

Hardness: 6.5-7 on Mohs scale. Color: Deep royal blue with translucent bands. Luster: Vitreous to waxy. Crystal structure: Hexagonal (cryptocrystalline). Cleavage: None (conchoidal fracture). Specific gravity: 2.60-2.65.

Formation & Geological History

Formed as a sedimentary or volcanic silica deposit. This specimen has been artificially dyed; naturally, it was likely gray or white agate formed in volcanic cavities. The dyeing process involves soaking the porous chalcedony in chemical solutions to enhance the color.

Uses & Applications

Commonly used for decorative ornaments, jewelry (beads, cabochons), crystal healing, and as polished pocket stones or tumbled gems.

Geological Facts

While sold as 'Blue Onyx', it is almost always dyed agate or chalcedony, as true blue onyx is extremely rare in nature. The practice of dyeing agate dates back to ancient Roman times.

Field Identification & Locations

Identify in the field by its banded texture and translucency. Natural blue chalcedony is usually pale lavender-blue, so intense royal blue signals artificial treatment. Commonly found in Brazil, India, and Madagascar.

Identified on: 4/28/2026

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