mineral

Banded Agate

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5–7; Color: Multi-colored bands (grey, white, brown); Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); SG: 2.6

Hardness: 6
Color: Multi-colored bands (grey, white, brown)
Luster: Waxy to vitreous

Identified July 18, 2026More mineral →

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Physical properties

Hardness: 6.5–7; Color: Multi-colored bands (grey, white, brown); Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); SG: 2.6

Formation & geological history

Formed primarily in volcanic rock cavities (vesicles) where silica-rich groundwater deposits layers of chalcedony over time. Often found in areas with ancient basaltic lava flows.

Uses & applications

Used extensively in jewelry (cabochons), lapidary arts, ornamental carvings, and historical precision tools like mortars and pestles.

Geological facts

The unique banding is caused by the rhythmic deposition of silica. Some agates, like the Lake Superior agate, are over a billion years old.

Field identification & locations

Identified by distinct concentric or parallel banding and waxy texture when broken. Commonly found in riverbeds, beaches, and glacial till. To identify, look for translucency when held to light.