mineral

Banded Chalcedony (Agate)

Cryptocrystalline Quartz (SiO2)

Hardness: 6.5–7 on Mohs scale; Color: White, cream, and yellow-orange with wavy concentric banding; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Fracture: Conchoidal.

Hardness: 6
Color: White, cream, and yellow-orange with wavy concentric banding
Luster: Waxy to vitreous

Identified July 18, 2026More mineral →

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Physical properties

Formation & geological history

Forms primarily through the deposition of silica from groundwater into cavities (vesicles) within igneous volcanic rocks or sedimentary limestone. The banding represents distinct pulses of silica-rich fluids over geological time.

Uses & applications

Used extensively in jewelry, lapidary arts (cabochons), as ornamental stones, and historically for precision bearings and mortars/pestles due to its hardness.

Geological facts

Agates are often found as 'lake stones' in glacial deposits. This specific specimen shows characteristic 'fortification' banding, which mimics the layout of old defensive fort walls.

Field identification & locations

Identify in the field by its translucency when held to light, waxy texture, and unique banding patterns. Commonly found in riverbeds, glacial tills, and volcanic regions like the Lake Superior area.

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Potassium Feldspar (Orthoclase)

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