sedimentary
Lake Superior Agate
Silicon Dioxide (Chalcedony), SiO2
AI-generated identification · may be incorrectMohs hardness of 6.5-7, waxy to vitreous luster, conchoidal fracture, and distinct concentric banding colored by iron oxides.
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Physical properties
Mohs hardness of 6.5-7, waxy to vitreous luster, conchoidal fracture, and distinct concentric banding colored by iron oxides.
Formation & geological history
Formed roughly 1.1 billion years ago via hydrothermal fluid deposition within gas cavities of basaltic lava flows.
Uses & applications
Prized by lapidaries and collectors for gemstone jewelry, cabochons, and ornamental displays.
Geological facts
It is the official state gemstone of Minnesota and features characteristic red, orange, and yellow iron-oxide color banding.
Field identification & locations
Identify by waxy luster, conchoidal fracture, and parallel or concentric color bands; found primarily in glacial drift around the Lake Superior region.
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