mineral

Lake Superior Agate

Silicon Dioxide (SiO2) - variety of Chalcedony

AI-generated identification · may be incorrect

Hardness: 6.5-7.0 (Mohs scale), Color: Red, orange, tan, and white bands/patches, Luster: Waxy to vitreous, Structure: Cryptocrystalline, Translucent to opaque

Hardness: 6

Identified July 20, 2026More mineral →

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Physical properties

Hardness: 6.5-7.0 (Mohs scale), Color: Red, orange, tan, and white bands/patches, Luster: Waxy to vitreous, Structure: Cryptocrystalline, Translucent to opaque

Formation & geological history

Formed roughly 1.1 billion years ago during the Keweenawan Rift when gas bubbles in basaltic lava flows were filled by mineral-rich groundwater, depositing thin layers of silica and iron oxides.

Uses & applications

Primarily used for gemstone collecting, jewelry (cabochons), and lapidary art due to its beautiful banding patterns and durability.

Geological facts

Designated as the official state gemstone of Minnesota in 1969; the coloring is primarily due to iron oxidation (limonite and hematite) during formation.

Field identification & locations

Commonly found on the shores of Lake Superior and in glacial drift throughout the Upper Midwest. Identify by its iron-rich red coloring and waxy translucency when wet.