Banded Agate (Gray/Blue Agate)

Physical Properties

Hardness: 6.5–7 on Mohs scale. Color: Translucent gray, white, and light blue with distinct concentric banding. Luster: Waxy to vitreous. Crystal system: Trigonal/Microcrystalline. Specific gravity: 2.58–2.64.

Formation & Geological History

Formed in cavities of volcanic rocks or ancient lavas (geodes) where silica-rich groundwater deposited layers of chalcedony over time. Typically forms in environments ranging from the Precambrian era to the Cenozoic era.

Uses & Applications

Used primarily in lapidary arts for jewelry, beads, and carvings. Historically used for making mortars and pestles due to hardness, and often used as a healing stone in metaphysical practices.

Geological Facts

Agate is named after the Achates River in Sicily where it was first discovered. The banding occurs due to rhythmic crystallization or periodic changes in the silica concentration during formation.

Field Identification & Locations

Identify by its translucency and distinct, consistent parallel or curved color bands. Commonly found in riverbeds or volcanic regions like those in Botswana, Brazil, and Lake Superior in the USA. Collectors look for sharp, high-contrast banding.

Identified on: 4/23/2026

Mode: Standard