mineral

Banded Agate

Chalcedony (Silicon Dioxide, SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Translucent white, tan, and brown with fine parallel banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.58-2.64.

Hardness: 6
Color: Translucent white, tan, and brown with fine parallel banding
Luster: Waxy to vitreous

Identified July 18, 2026More mineral →

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Physical properties

Formation & geological history

Formed via the deposition of silica from groundwater into the cavities of igneous rocks such as basalt or volcanic rhyolite. The banding results from rhythmic crystallization of layers within the gas bubbles (vesicles) or cracks.

Uses & applications

Commonly used in jewelry as cabochons, for ornamental carvings, tumble polishing for collectors, and historically for functional tools like mortar and pestles due to its hardness.

Geological facts

Agate is named after the Achates River in Sicily where it was first discovered. The 'fortification' banding patterns seen in this specimen are unique to each individual stone, similar to a fingerprint.

Field identification & locations

Identify in the field by looking for translucent nodules with smooth, waxy surfaces and curved 'conchoidal' fracture patterns. Often found in riverbeds or near ancient volcanic ash deposits. Common locations include Brazil, India, and the United States (Lake Superior region).