mineral

Banded Agate (specifically Lake Superior Agate style)

Agate (Cryptocrystalline Quartz, SiO2)

Hardness: 6.5-7 (Mohs scale), Color: Concentric bands of red, brown, and white, Luster: Waxy to vitreous, Crystal Structure: Hexagonal (Microcrystalline), Cleavage: None, Specific Gravity: 2.60-2.65

Hardness: 6

Identified May 30, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Concentric bands of red, brown, and white, Luster: Waxy to vitreous, Crystal Structure: Hexagonal (Microcrystalline), Cleavage: None, Specific Gravity: 2.60-2.65

Formation & geological history

Formed in gas bubbles (vesicles) of basaltic lava flows approximately 1.1 billion years ago during the Midcontinent Rift. Iron-rich silica groundwater later filled these cavities, depositing layers of chalcedony.

Uses & applications

Commonly used in jewelry (cabochons), as tumbled pocket stones, in decorative carvings, and as a popular focus for lapidary collectors.

Geological facts

Agate is the state gemstone of Minnesota. The red coloration is typically caused by iron oxidation (limonite or hematite) within the silica bands.

Field identification & locations

Identify in the field by looking for concentric 'eye' or 'fortification' banding and a waxy texture. Frequently found on gravel beaches of Lake Superior or in glacial till across the Upper Midwest USA.

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