gemstone

Yellow agate (chalcedony)

Microcrystalline quartz, SiO₂; chalcedony variety, possibly colored or treated

AI-generated identification · may be incorrect

Yellow, translucent to opaque, waxy-to-vitreous luster, typically Mohs 6.5–7 and trigonal quartz structure; the small, rounded piece shows no obvious banding. Hardness and composition cannot be confirmed from the image alone.

Identified October 8, 2026More gemstone →

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Physical properties

Formation & geological history

Agate forms as silica-rich fluids fill cavities in volcanic rock and deposit layers over time; deposits occur in rocks of many ages. The piece appears cut or shaped and may be polished or treated.

Uses & applications

Used for beads, pendants, carvings, and decorative objects; chalcedony is also used for small ornamental and historical tool objects.

Geological facts

Agate is chalcedony, a fine-grained form of quartz; visible bands are common but not required for a piece to be agate.

Field identification & locations

Look for waxy luster, translucency, hardness near 7, and—where present—concentric bands; common sources include Brazil, Uruguay, India, and the United States. The photo is insufficient to distinguish agate from other yellow chalcedony or to assess treatment.