GOLDEN VALLEY, Minn. - Minnesota's state gemstone is the Lake Superior agate, and for years it has fascinated those young and old.

In response to a viewer question from our kiosk at the Science Museum of Minnesota, KARE 11's Laura Betker worked to find the answer to Ian Wagner's question.

"I was wondering how Lake Superior agates are formed," Wagner wrote.

Over 1 billion years ago, lava flowed through in the area we now know as Lake Superior. As the lava cooled, air pockets filled with mineral rich water, depositing layers of chalcedony quartz that hardened together to form agates.

Glaciers then moved the agates south through Minnesota, Wisconsin and Iowa, where they can be found today in gravel pits, river beds and farmer's fields.

"Maple Grove is an agate hot spot, as is Apple Valley," points out Excelsior's Jim Stiller.

Agate enthusiasts like Stiller collect, buy and sell the gemstones. His favorite is a four and a half pounder that was found in northwestern Wisconsin.

Lake Superior Agates, in particular, are known for their contrasting white and red layers, called banding. Deposits of iron give the Lake Superior agates that trademark red color.
Brazilian agates are full of blues and greens. Laguna Lace agates come from Mexico.

The aptly named eye agates are believed to have been formed with minerals dripping into the lava cavities as the agate was forming.

It all began more than a billion years ago, but agates are still turning up today. And no two are exactly alike.

Agates of all shapes and sizes will be showcased through this weekend at Hopkins High School for the Minnesota Mineral Club's "a Celebration of Agates".

Visit the clubs website for more information at

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