Banded Agate

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Gray, light blue, and white; 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-rich groundwater within cavities (vugs) in volcanic or sedimentary rocks. The distinct banding represents different stages of mineral deposition over thousands of years.

Uses & Applications

Primarily used for ornamental purposes, lapidary art, jewelry (cabochons), and as collectibles. Historically used for making mortars and pestles due to hardness.

Geological Facts

Agate was named by Theophrastus, a Greek philosopher, who discovered the stone along the shore line of the river Achates in modern-day Sicily. It is a variety of chalcedony.

Field Identification & Locations

Identify in the field by its characteristic concentric or parallel banding and waxy texture when polished. Often found in riverbeds or volcanic regions like Brazil, India, and the Lake Superior region.

Identified on: 5/2/2026

Mode: Standard