mineral

Banded Agate (Lake Superior Agate style)

Cryptocrystalline Quartz (SiO2)

Hardness: 7 on Mohs scale; Color: Red, orange, white, and gray banding; Luster: Waxy to vitreous; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.64

Hardness: 7 on Mohs scale
Color: Red, orange, white, and gray banding
Luster: Waxy to vitreous

Identified June 28, 2026More mineral →

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Physical properties

Formation & geological history

Formed in gas bubbles (vesicles) within ancient basaltic lava flows approximately 1.1 billion years ago during the Midcontinent Rift. Iron-rich groundwater later deposited microscopic quartz layers within these cavities.

Uses & applications

Commonly used for jewelry (cabochons), lapidary art, aquarium decoration, and as a popular collector's gemstone due to its unique patterns.

Geological facts

Lake Superior Agates are the state gemstone of Minnesota. The red coloration is caused by the oxidation of iron within the silica layers.

Field identification & locations

Identify by looking for translucent parallel banding and a 'waxy' texture. Often found in glacial till, gravel pits, and along the shores of the Great Lakes. Collectors look for 'eyes' or tight banding.

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Mineral

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Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock