Lake Superior Agate

Physical Properties

Hardness: 7 Mohs; Color: Red, orange, white, and translucent; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific gravity: 2.60-2.65

Formation & Geological History

Formed in gas vesicles (bubbles) of basaltic lava flows approximately 1.1 billion years ago during the Midcontinent Rift system. Iron leached from the basalt provides the signature red and orange coloration.

Uses & Applications

Highly prized by collectors, used in lapidary work for jewelry, tumbling, and decorative display pieces.

Geological Facts

The Lake Superior Agate was designated as the official state rock of Minnesota in 1969. It is famous for its concentration of iron-rich red bands.

Field Identification & Locations

Identified by concentric banding, waxy texture, and translucency. Commonly found on beaches of Lake Superior and in glacial till throughout the Upper Midwest, particularly Minnesota and Wisconsin. Collectors look for 'windows' into the banding.

Identified on: 5/19/2026

Mode: Standard