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 red, orange, and yellow concentric banding 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 red, orange, and yellow concentric banding caused by iron oxides.
Formation & geological history
Formed roughly 1.1 billion years ago when hydrothermal fluids filled gas cavities in basaltic lava flows, later weathering out into glacial drifts.
Uses & applications
Cut and polished into cabochons for jewelry, or collected as prized lapidary and mineral specimens.
Geological facts
It is the official state gemstone of Minnesota and is renowned for its rich red-and-white banding formed by varying oxidation states of iron.
Field identification & locations
Identified by its waxy luster, conchoidal fracture, and prominent iron-stained color bands; found primarily in glacial gravels and riverbeds of the Upper Midwest USA.
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