mineral

Banded Agate

Chalcedony (Silicon Dioxide, SiO2)

Hardness: 6.5–7 on the Mohs scale. Color: Translucent grey to white center with brown, tan, and reddish banding. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (hexagonal/trigonal). Cleavage: None. Specific gravity: 2.58–2.64.

Hardness: 6
Luster: Waxy to vitreous

Identified March 9, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary mineral in cavities of volcanic igneous rocks (basalt or andesite) or sedimentary rocks. It deposits in layers from silica-rich groundwater. Geological age varies greatly, often found in formations dating back millions of years.

Uses & applications

Primary uses include lapidary arts such as jewelry (pendants, beads), ornamental carvings, and historically used for mortars and pestles due to its hardness and resistance to chemicals.

Geological facts

The name 'Agate' comes from the Achates River in Sicily. No two agates are identical because the banding is formed by rhythmic crystallization influenced by changing mineral impurities during formation.

Field identification & locations

Identify in the field by its waxy luster on fractured surfaces and its characteristic concentric or planar banding. Commonly found in riverbeds, beaches, and volcanic regions in places like Brazil, Uruguay, and the Lake Superior region of the US.