Banded Agate (Yellow Agate)

Physical Properties

Hardness: 6.5-7 (Mohs); Color: Pale yellow, creamy white, to golden tan; Luster: Waxy to vitreous; Crystal structure: Hexagonal (trigonal) - cryptocrystalline microstructures; Cleavage: None; Specific gravity: 2.58–2.64

Formation & Geological History

Formed primarily in volcanic and metamorphic rocks. It occurs when silica-rich groundwater fills cavities (vesicles) in igneous rocks, cooling and depositing microcrystalline quartz in layers over thousands of years.

Uses & Applications

Primarily used for decorative purposes, lapidary carvings into points or towers, jewelry (cabochons), and as a collector's specimen. In industry, it can be used for mortar and pestles due to its hardness.

Geological Facts

Agate is a variety of chalcedony. The banding in agates is thought to be caused by changes in the impurity levels or the rate of crystallization during formation. The specimen in the image has been cut and polished into an 'obelisk' or 'point' shape.

Field Identification & Locations

Identify in the field by its distinct concentric or parallel banding, waxy appearance, and conchoidal fracture. Often found as nodules in stream beds or weathered volcanic fields. Common locations include Brazil, India, and the USA.

Identified on: 5/10/2026

Mode: Standard