mineral

Lake Superior Agate

Silicon Dioxide (SiO2) with iron impurities

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

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

Identified June 28, 2026More mineral →

Explore Lake Superior Agate in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Formed roughly 1.1 billion years ago during the Midcontinent Rift System. As lava cooled, gas bubbles created cavities which were later filled by silica-rich groundwater and iron oxides, creating distinct concentric bands.

Uses & applications

Primarily used for lapidary work, jewelry (cabochons), and as a highly sought-after collectible specimen. It is the official state gem of Minnesota.

Geological facts

Lake Superior Agates are unique because they were distributed across large areas of the Midwest by glaciers during the last ice age, rather than remaining in their volcanic source rock.

Field identification & locations

Identify in the field by looking for translucent waxy surfaces, distinct 'fortification' banding, and a pitted 'peel' or husk. Commonly found on beaches of Lake Superior, gravel pits, and riverbeds 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

Gypsum (variety Selenite or Alabaster)

Calcium sulfate dihydrate (CaSO4·2H2O)

Mineral

Nephrite Jade

Nephrite

Mineral/Rock

Banded Gneiss (River Rock/Pebble)

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

Metamorphic Rock