mineral

Banded Agate (Lake Superior Agate variant)

Silicon Dioxide (SiO2)

Hardness: 7 Mohs; Color: Tan, white, orange, and amber bands; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65

Hardness: 7 Mohs
Color: Tan, white, orange, and amber bands
Luster: Waxy to vitreous

Identified June 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed as silica-rich groundwater deposited layers inside gas bubbles (vesicles) of basaltic lava approximately 1.1 billion years ago during the Midcontinent Rift. Glacial activity later scattered these specimens from their original volcanic sources.

Uses & applications

Highly valued for lapidary work including cabochons, jewelry, and ornamental carvings. Popular as a collectible mineral and state gemstone of Minnesota.

Geological facts

This specific specimen shows the classic concentric banding patterns typical of agates. The iron content in the groundwater during formation provides the distinct yellow and orange hues seen in the bands.

Field identification & locations

Identify in the field by looking for translucent banding, a waxy texture, and a pitted 'peeling' husk. Common in glacial till and gravel pits across the Upper Midwest USA, particularly Minnesota, Wisconsin, and Michigan.

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Mineral/Rock

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mineral