mineral

Banded Agate (Lake Superior or Jasper-Agate)

Silicon dioxide (SiO2)

Hardness: 6.5-7 (Mohs), Color: Red, white, gray, and cream banding, Luster: Waxy to vitreous when polished, Structure: Microcrystalline quartz, Cleavage: None (conchoidal fracture), Specific Gravity: 2.58-2.64

Hardness: 6

Identified June 21, 2026More mineral →

Explore Banded Agate (Lake Superior or Jasper-Agate) in the encyclopedia →

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Physical properties

Formation & geological history

Formed roughly 1.1 billion years ago during the Midcontinent Rift. Silica-rich groundwater filled gas bubbles (vesicles) in volcanic basalt flows, precipitating layers of chalcedony over time.

Uses & applications

Mainly used for lapidary arts, jewelry (cabochons), and as a popular collector's item due to its aesthetic banding and high polish.

Geological facts

The red coloring is caused by the oxidation of iron. These agates were distributed across the Midwest by glacial movements during the last ice age, making them easy to find in gravel pits and beaches.

Field identification & locations

Identify by looking for distinct concentric or parallel banding and a waxy translucency. Common in the Lake Superior region and glacial drift areas of Minnesota, Wisconsin, and Michigan.

Other mineral specimens

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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