sedimentary
Lake Superior Agate
Silicon dioxide (chalcedony), SiO2
AI-generated identification · may be incorrectHardness of 6.5 to 7 on the Mohs scale, waxy luster, conchoidal fracture, and distinct parallel curved banding of red, brown, and yellow caused by iron oxides.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy luster, conchoidal fracture, and distinct parallel curved banding of red, brown, and yellow caused by iron oxides.
Formation & geological history
Formed roughly 1.1 billion years ago when hydrothermal fluids deposited silica into gas cavities in basaltic lava flows.
Uses & applications
Prized by lapidaries for cutting and polishing into cabochons for jewelry, and heavily sought after by rockhounds.
Geological facts
They are the official state gemstone of Minnesota and display rich red and orange colors due to iron-rich glacial environments.
Field identification & locations
Identified by concentric multicolored banding, waxy texture, and pocket cavities; commonly found in glacial drift around the Upper Midwest of the US.
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