mineral

Lake Superior Agate

Agate (Cryptocrystalline variety of Quartz, SiO2)

Hardness: 7 Mohs scale; Color: Red, orange, and white banding; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.60-2.65

Hardness: 7 Mohs scale
Color: Red, orange, and white banding
Luster: Vitreous to waxy

Identified June 13, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 7 Mohs scale; Color: Red, orange, and white banding; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.60-2.65

Formation & geological history

Formed roughly 1.1 billion years ago during the Keweenawan Rift. Gas bubbles trapped in cooling lava flows (basalt) were later filled with silica-rich groundwater, depositing thin layers of quartz and iron impurities.

Uses & applications

Polished for jewelry, used in lapidary art, and highly prized by mineral collectors.

Geological facts

The Lake Superior Agate was designated as the official state gem of Minnesota in 1969. The red color is caused by iron oxidation (limonite and hematite) during formation.

Field identification & locations

Identify by looking for distinct concentric banding, translucent quartz areas, and a waxy surface texture. They are commonly found in glacial gravel pits and along the shores of Lake Superior in Minnesota, Wisconsin, and Michigan.

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

Biotite Schist

Biotite-rich Schist [K(Mg,Fe)3AlSi3O10(F,OH)2]

metamorphic