Yellow Agate

Physical Properties

Hardness 6.5-7 on the Mohs scale; Color: honey yellow to amber; Luster: vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: none; Specific gravity: approx 2.6.

Formation & Geological History

Forms primarily in volcanic and metamorphic rocks as a result of silica-rich groundwater filling cavities (vugs). Age varies but can date back millions of years depending on the host rock formation.

Uses & Applications

Commonly used in jewelry, ornamental carvings, tumbling/polishing for collectors, and historically for making burnishing tools.

Geological Facts

Agate is a variety of chalcedony. The yellow coloring is often caused by the inclusion of iron oxides or hydroxide minerals within the silica structure.

Field Identification & Locations

Identify by its translucent nature, waxy luster, and conchoidal fracture. Commonly found in riverbeds or volcanic regions in Brazil, India, and the USA.

Identified on: 4/25/2026

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