sedimentary
Lake Superior Agate
Silicon Dioxide (Chalcedony), SiO2
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, waxy to vitreous luster, concentric banding in red, orange, and brown colors, cryptocrystalline structure.
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Physical properties
Hardness of 7 on the Mohs scale, waxy to vitreous luster, concentric banding in red, orange, and brown colors, cryptocrystalline structure.
Formation & geological history
Formed roughly 1.1 billion years ago when hydrothermal fluids filled gas cavities in basaltic lava flows.
Uses & applications
Used primarily in lapidary arts, wire-wrapping, and polished as semi-precious jewelry gemstones.
Geological facts
It is the official state gemstone of Minnesota and is renowned for its rich red and orange iron-oxide banding.
Field identification & locations
Identify by conchoidal fracture, waxy luster, and distinct multicolored concentric rings; found mainly in glacial drift around the Upper Midwest of the US.
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Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
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Sandstone or Siltstone
Arenite (if sandstone)
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Sandstone
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Shale
Shale (clastic sedimentary rock)
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Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
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