mineral

Banded Agate

Chalcedony (SiO2 with impurities)

Hardness: 6.5-7 on Mohs scale; Color: Red, orange, white, and gray bands; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.64

Hardness: 6
Color: Red, orange, white, and gray bands
Luster: Waxy to vitreous

Identified July 13, 2026More mineral →

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Physical properties

Formation & geological history

Formed in cavities of volcanic rocks or ancient lavas, where silica-rich fluids deposit layers of chalcedony over time, creating distinctive banding. Most specimens range from hundreds of thousands to millions of years old.

Uses & applications

Extensively used in jewelry (cabochons, beads), decorative carvings, and industrially for precision pendulums, mortars and pestles due to its hardness and chemical resistance.

Geological facts

Agate was first named by the Greek philosopher Theophrastus in the 4th century BCE after the Achates River in Sicily where it was discovered. It belongs to the quartz family but is specifically a variety of chalcedony.

Field identification & locations

Look for distinctive concentric or surface-parallel banding. In the field, look for translucent waxy edges and a heavy feel for its size. Common locations include Brazil, Uruguay, and the Lake Superior region of the USA.