sedimentary
Lake Superior Agate
Silicon Dioxide (Chalcedony)
AI-generated identification · may be incorrectHardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, banded concentric patterns in red, brown, and yellow, with a specific gravity of 2.65.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, banded concentric patterns in red, brown, and yellow, with a specific gravity of 2.65.
Formation & geological history
Formed roughly 1.1 billion years ago during the Keweenawan Rift Zone volcanism through the deposition of silica-rich groundwater in gas cavities of basalt.
Uses & applications
Widely used in lapidary arts, jewelry making, and highly prized by rockhounds and mineral collectors.
Geological facts
They are the official state gemstone of Minnesota and display characteristic iron-oxide staining that provides their rich red and orange hues.
Field identification & locations
Identified by distinct concentric color banding and a waxy luster, commonly found in glacial drift throughout the upper Midwestern United States.
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