mineral

Banded Agate (specifically Lake Superior Agate)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Red, orange, white, tan, and brown bands. Luster: Waxy to vitreous. Crystal Structure: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None, conchoidal fracture.

Hardness: 6
Color: Red, orange, white, tan, and brown bands
Luster: Waxy to vitreous

Identified June 28, 2026More mineral →

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Physical properties

Formation & geological history

Formed roughly 1.1 billion years ago during the Keweenawan Rift. Gas bubbles in basaltic lava flows were filled by silica-rich water, with iron impurities creating the red and orange bands.

Uses & applications

Primarily used for jewelry (cabochons), lapidary art, and popular as a collector's item due to its unique fortification patterns.

Geological facts

The Lake Superior Agate is the official state gem of Minnesota. The V-shaped bands seen in this specimen are often called fortification patterns.

Field identification & locations

Identified by its distinctive concentric or V-shaped banding and translucent layers. Often found in gravel pits and on beaches in the Upper Midwest United States, especially along Lake Superior shores.

Other mineral specimens

See all

Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Schist

Metamorphic

Epidote

Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

metamorphic

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

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

Metamorphic Rock

Green Apatite on Albite

Fluorapatite [Ca5(PO4)3F] on Albite [Na(AlSi3O8)]

mineral