Agate

Physical Properties

Hardness: 6.5-7 (Mohs scale), Color: Pale yellow-grey to translucent, Luster: Vitreous to waxy, Crystal structure: Trigonal/Microcrystalline, Cleavage: None, Specific gravity: 2.58-2.64

Formation & Geological History

Formed as a secondary mineral in volcanic cavities (vesicles) through the deposition of silica from groundwater. Usually Cretaceous to Tertiary in age.

Uses & Applications

Used primarily for lapidary arts, jewelry (cabochons), burnishing tools, and as ornamental display pieces.

Geological Facts

Agate is a variety of chalcedony. This specimen demonstrates the typical 'frosted' or tumbled outer rind common in river-worn or beach-collected stones.

Field Identification & Locations

Look for a waxy luster and conchoidal (shell-like) fracture. Found worldwide in volcanic regions, notably Brazil, Uruguay, and the Lake Superior region in the US.

Identified on: 5/13/2026

Mode: Standard