mineral

Banded Agate

Sedimentary Cryptocrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, tan, and orange banding; Luster: Waxy to vitreous; Crystal Structure: Hexagonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.64

Hardness: 6
Color: Reddish-brown, tan, and orange banding
Luster: Waxy to vitreous

Identified May 17, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, tan, and orange banding; Luster: Waxy to vitreous; Crystal Structure: Hexagonal (cryptocrystalline); Cleavage: None; Specific Gravity: 2.58-2.64

Formation & geological history

Formed primarily in volcanic rock cavities or ancient sedimentary layers. As groundwater rich in silica seeps into these cavities, layers of microcrystalline quartz deposit over time, creating the characteristic banding. This specimen appears to be the 'Lake Superior' or 'Carnelian' variety based on iron-oxide coloring.

Uses & applications

Used extensively in jewelry (cabochons, beads), decorative carvings, and as a popular collector's item due to its aesthetic banding. Historically used for making burnishing tools and mortars/pestles.

Geological facts

Agate is named after the Achates River in Sicily where it was first discovered. The banding provides a chronological record of the geochemical environment at the time of each layer's formation.

Field identification & locations

Identify in the field by its translucent edges, waxy texture when polished, and distinct parallel banding. Common in the Great Lakes region, Brazil, and India. Look for 'conchoidal' (shell-like) fractures on unpolished surfaces.

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