MyNorth.com has some tips for agate-hunting on Lake Superior:

Claim to fame: Lake Superior agates are the oldest agates on earth, formed 1.2 billion years ago. The next oldest are the Montana moss agates, a mere 370 million years old.

The most prized: Highly contrasting red and white bands (called candy stripers), eye-like patterns (eye agates) and hologramlike appearance (shadow agates).

Hunting grounds: Comb any pebbly beach on the south and west shores of Lake Superior, but the beaches near Grand Marais are famed for their agates.

What to look for: A pitted or peeled texture. A glossy, waxy appearance on chipped surfaces. Rust- and yellow-hued iron oxide staining. Translucence produced by their quartz content, causing a glow easily observed on sunny days, or when the rock is backlit with a flashlight.

When to look: Best hunting is right after a storm with churning waves.

More here…

http://www.mynorth.com/My-North/August-2008/Beach-Comb-for-Superior-Agates/

Note: The image above is from the State of Minnesota’s web site.

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