Banded Agate

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Tan, brown, white, and translucent layers; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.64

Formation & Geological History

Formed through the deposition of silica from groundwater in the cavities of igneous rocks, particularly volcanic lavas. The banding is created by successive layers of silica-rich fluids over thousands of years.

Uses & Applications

Polished for use in jewelry (cabochons, beads), decorative ornaments, stone carvings, and as a popular lapidary material for hobbyists.

Geological Facts

Agate is named after the Achates River in Sicily, where it was first discovered. The distinctive banding is often rhythmic and can be used to tell the chemical history of the fluid that deposited it.

Field Identification & Locations

Identify by its characteristic parallel, curved, or concentric banding and its hardness; it will easily scratch glass. Commonly found in riverbeds, volcanic fields, and agate-rich regions like Lake Superior or Brazil.

Identified on: 5/10/2026

Mode: Standard