Chalcedony (Common Agate pebble)

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: translucent honey-yellow to brownish-orange; Luster: waxy to vitreous; Crystal structure: cryptocrystalline (microscopic quartz); Cleavage: none, conchoidal fracture.

Formation & Geological History

Formed through the deposition of silica from groundwater in cavities of volcanic or sedimentary rocks. This specimen is water-worn, likely from a river or beach environment.

Uses & Applications

Used for lapidary work, jewelry (beads and cabochons), decorative stones, and as a collector's specimen.

Geological Facts

Chalcedony is a cryptocrystalline form of silica, meaning its crystals are so small they can only be seen under a microscope. It is the base mineral for agate, carnelian, and onyx.

Field Identification & Locations

Identify by its waxy luster, translucency when held to light, and its ability to scratch glass. Commonly found in gravel pits, riverbeds, and along shorelines.

Identified on: 4/29/2026

Mode: Standard