mineral

Lake Superior Agate

Chalcedony (SiO2 with iron impurities)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Red, orange, tan, and white banding; Luster: Vitreous to waxy; Crystal structure: Hexagonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific gravity: 2.58-2.64

Hardness: 6
Color: Red, orange, tan, and white banding
Luster: Vitreous to waxy

Identified July 18, 2026More mineral →

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Physical properties

Formation & geological history

Formed roughly 1.1 billion years ago during the Midcontinent Rift. Silica-rich groundwater deposited layers of quartz inside gas vesicles (bubbles) of volcanic basalt lava flows. Glaciation later dispersed these specimens across the Midwest.

Uses & applications

Used primarily in lapidary arts for jewelry, tumbled stones, and collector displays. Small specimens like this are common in rock tumbling.

Geological facts

The Lake Superior Agate was designated the official state gem of Minnesota in 1969. Its distinctive red color comes from iron leached from local iron ores during formation.

Field identification & locations

Identify by looking for concentric banding, a 'waxy' texture when dry, and a translucent quality when held to a light. Commonly found on beaches of Lake Superior and in gravel pits across Minnesota, Wisconsin, and Iowa.