gemstone

Polished agate bracelet (likely gray chalcedony)

Microcrystalline quartz, SiO₂; chalcedony/agate variety

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent gray-blue to brown banding, vitreous-to-waxy luster, cryptocrystalline quartz structure, and no visible cleavage. The smooth, highly polished ring is a shaped human-processed geological specimen.

Identified September 5, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, depositing microscopic quartz and chalcedony in layers; ages range from Cenozoic to Paleozoic depending on the deposit. The bracelet was cut and polished from lapidary rough.

Uses & applications

Used for bracelets, cabochons, beads, carvings, and ornamental objects; durable and affordable jewelry material.

Geological facts

Agate’s concentric or irregular bands reflect changing chemistry during repeated silica deposition. Gray chalcedony may also be marketed as onyx, although true onyx typically has straighter parallel bands.

Field identification & locations

Identify by glassy/waxy luster, translucency, fine banding, and resistance to scratching by ordinary steel; glass should not scratch it, while quartz can. Common sources include Brazil, Uruguay, India, Madagascar, Mexico, and the United States.