gemstone

Lake Superior Agate

Silicon Dioxide (Chalcedony / Quartz)

Hardness of 7 on the Mohs scale, predominantly red, orange, and yellow hues due to iron oxide staining, waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture with no cleavage, and a specific gravity of around 2.60 to 2.65.

Identified August 5, 2026More gemstone →

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Physical properties

Formation & geological history

Formed roughly 1.1 billion years ago during the Keweenawan Rift Zone event, where gas cavities in basaltic lava flows were filled with silica-rich hydrothermal fluids in rhythmic concentric bands.

Uses & applications

Used primarily in lapidary arts, wire wrapping, making jewelry such as pendants and rings, and highly sought after by mineral and rock collectors.

Geological facts

Lake Superior agates are the state gemstone of Minnesota and are famous for their rich red, orange, and yellow colors caused by oxidized iron, shaped extensively by glacial activity.

Field identification & locations

Can be identified by its distinctive concentric banding, waxy luster, translucency on thin edges, and conchoidal fracture; commonly found in glacial drift, gravel pits, and along the shores of Lake Superior and surrounding Midwestern states.

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Gemstone Ring

N/A - Set piece of jewelry, likely Amethyst or Garnet with Diamond or CZ

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Diamond and Gold Jewelry

Carbon (Diamond) / Au (Gold)

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Ammolite

Ammolite (Biogenic Aragonite with trace elements; fossils of Placenticeras meeki and Placenticeras intercalare)

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Cubic Zirconia (simulant) or Diamond

ZrO2 (Cubic Zirconia) or C (Diamond)

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Red Jasper

Silicon Dioxide (SiO2) with Hematite inclusions

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Black Opal Ring (Carved Opal)

Hydrated Silicon Dioxide (SiO2·nH2O)

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