sedimentary
Lake Superior Agate
Silicon dioxide (Chalcedony / Quartz)
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, banded color patterns typically featuring red, orange, and yellow due to iron oxide staining, cryptocrystalline structure, conchoidal fracture, specific gravity around 2.6.
Identified More sedimentary →
Explore Lake Superior Agate in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, banded color patterns typically featuring red, orange, and yellow due to iron oxide staining, cryptocrystalline structure, conchoidal fracture, specific gravity around 2.6.
Formation & geological history
Formed in gas cavities of ancient basaltic lava flows over 1.1 billion years ago during the Keweenawan rifting event, later released by weathering and transported by glacial activity.
Uses & applications
Prized by rockhounds and lapidary artists for jewelry, cabochons, and display collections.
Geological facts
Lake Superior agates are the official state gemstone of Minnesota and are famous for their rich red and orange banding caused by varying oxidation states of iron.
Field identification & locations
Easily identified in the field by their distinct concentric color banding, waxy luster, and translucent to opaque layers. Commonly found in gravel pits, riverbeds, and glacial tills around the Great Lakes region of North America.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Generic Pebble / Rock Fragment
Lithic fragment / Weathered rock
sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Banded Siltstone / Mudstone Pebble
Siltstone / Argillite
sedimentary