gemstone

Lake Superior Agate

Silicon Dioxide (Chalcedony variety)

Hardness: 6.5-7 on the Mohs scale; Color: Red, orange, yellow, brown, and white banding; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline quartz); Cleavage: None (conchoidal fracture); Specific gravity: 2.60-2.65

Hardness: 6
Color: Red, orange, yellow, brown, and white banding
Luster: Waxy to vitreous

Identified August 3, 2026More gemstone →

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Physical properties

Formation & geological history

Formed roughly 1.1 billion years ago during the Keweenawan Rift Zone volcanism. Silica-rich fluids deposited layers of quartz inside gas cavities (vesicles) within basaltic lava flows.

Uses & applications

Used primarily in lapidary arts, tumbled stones, custom jewelry, and by mineral collectors.

Geological facts

Lake Superior agates are the official state gemstone of Minnesota and are famous for their rich red and orange banding caused by iron oxidation.

Field identification & locations

Found primarily in the Upper Midwest of the United States (Minnesota, Wisconsin, Michigan) in glacial drift, gravel pits, and along lake shores. Identified by distinctive concentric color banding and waxy luster.

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