Yellow Chalcedony (Agate Pebble)

Physical Properties

Hardness: 6.5–7 (Mohs scale); Color: Yellow to honey-orange; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58–2.64

Formation & Geological History

Formed through the deposition of silica from groundwater in cavities of volcanic and sedimentary rocks. This specific specimen appears water-worn, suggesting it was tumbled in a river or beach environment long after its initial formation in the Cenozoic or Mesozoic era.

Uses & Applications

Commonly used in lapidary work for cabochons, beads, and tumbled stones. In industry, it was historically used for mortar and pestle sets due to its hardness, though now it is primarily ornamental.

Geological Facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are too small to be seen even under a normal microscope. Yellow varieties are sometimes trade-named 'Honey Agate' when they show translucent qualities.

Field Identification & Locations

Identify in the field by its waxy luster, smoothness (if water-worn), and the fact that it cannot be scratched by a steel knife. It is commonly found in gravel beds, shorelines, or weathered volcanic ash deposits.

Identified on: 4/15/2026

Mode: Standard