Chalcedony (Yellow Agate)

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Pale yellow to honey-orange (waxy translucency); Luster: Vitreous to waxy; Crystal structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture)

Formation & Geological History

Formed by the deposition of silica from groundwater in cavities of igneous rocks such as basalt, or in sedimentary environments. Its age can range from recent to hundreds of millions of years.

Uses & Applications

Used primarily in jewelry (cabochons and beads), decorative carvings, and as a popular specimen for mineral collectors.

Geological Facts

Agate is often confused with common quartz, but its microscopic crystalline structure makes it tougher and less prone to shattering. Yellow agate is sometimes associated with willpower and clarity in metaphysical circles.

Field Identification & Locations

Identify by its characteristic waxy luster and translucency. It will scratch glass but cannot be scratched by a steel knife. Common in riverbeds and volcanic regions worldwide, including Brazil and the USA.

Identified on: 5/13/2026

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