Banded Agate

Physical Properties

Hardness: 6.5-7 on Mohs scale; Color: Gray, white, and translucent black; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None/Conchoidal fracture; Specific gravity: 2.58-2.64

Formation & Geological History

Formed in cavities within volcanic or metamorphic rocks when silica-rich groundwater deposits layers of chalcedony over time. These layers often correspond to changes in the chemistry of the water.

Uses & Applications

Used extensively in jewelry (cabochons, beads), decorative carvings, precision pendulums, and as mortar and pestles for chemical testing due to its hardness and acid resistance.

Geological Facts

The name 'Agate' comes from the Achates River in Sicily, where the mineral was first discovered in ancient times. Every agate is unique due to the specific conditions under which its concentric bands formed.

Field Identification & Locations

Identified by its distinctive concentric color banding and translucent quality when held to light. Frequently found in riverbeds, gravel deposits, and volcanic areas in Brazil, India, and the United States (Lake Superior).

Identified on: 5/2/2026

Mode: Standard