Lake Superior Agate — Iron-Banded Fortification Pattern, Glacial Tumbled, 155g — Field Find

THE FIND
A Lake Superior agate, 155g — rich iron-stained bands of burnt red, rust orange, deep brown, and smoky translucence in the characteristic fortification pattern. Formed in ancient volcanic rock, released by glaciers, and naturally tumbled by ice and water over thousands of years. A piece of deep American geological time.

WHAT WE KNOW
Lake Superior agates are a specific variety of fortification agate formed approximately 1.1 billion years ago in the basaltic lava flows of the Midcontinent Rift System — one of the largest failed continental rift events in Earth’s history. The characteristic iron-rich banding (burnt reds, oranges, and browns) is produced by hematite and goethite deposited in the silica bands during formation. The stones were later transported and naturally tumbled by the Laurentide Ice Sheet during the Pleistocene glaciations, distributing them across Minnesota, Wisconsin, Iowa, and the Great Lakes region. This specimen weighs 155g. Locality attributed to the Lake Superior region.

THE STORY
Lake Superior agates are among the oldest agates on Earth — formed 1.1 billion years ago in a rift that nearly split the North American continent in two. The rift failed, the lava cooled, and the agates formed in the cavities. Then, roughly 10,000–20,000 years ago, glaciers picked them up and carried them south, tumbling and polishing them in the process. What you’re holding is a stone that survived a billion years of geological history and a continental ice sheet. The iron banding is the color of that survival.

WHY WE CHOSE IT
The fortification banding on this piece is well-developed and clearly visible — the iron-red and orange bands are saturated and distinct. At 155g it has real presence as a display specimen. Lake Superior agates are one of the few American-origin minerals with a geological story that genuinely competes with anything from overseas.

ABOUT THIS PIECE
Type: Lake Superior agate (fortification agate, iron-banded chalcedony)
Origin: Lake Superior region, Upper Midwest
Weight: 155g
Condition: Naturally tumbled specimen — please review photographs for banding, color, and natural variation.
Quantity: 1 — one of a kind.