Karen “Agatelady” Bryzs of the Gitchee Gumee Museum in Grand Marais shares a ton of information about Lake Superior Agates, part of a worldwide family of semi-precious gemstones that naturally develop when an empty pocket inside a host rock fills in with microcrystals, forming a totally unique pattern:
Most Lake Superior agates formed in a rift zone approximately 1.2 billion years ago. Rift zones are cracks in the Earth’s surface out of which molten lava flowed. Today, there are still rift zones at the bottom of the Pacific and Atlantic oceans. The rift zone that created Lake Superior agates started in what is now northeast Kansas and continued northeast into what is now the western end of Lake Superior. This hot spot domed up lava several miles high and eventually choked itself off. If it would have continued, it could have split the North American continent in half.
She offers some tips from her book “Understanding and Finding Agates“:
- Scan the beach and look for the Iron oxide red color.
- Look for rocks that show evident concentric banding.
- Check for possible entrance and/or escape channels that allowed gases or originally escape from the cavity, silica-rich water to enter, and pressure formed during the agate precipitation process to escape.
- Search for rocks with conchoidal fractures that give the specimen a more angular, irregular shape.
- When the angle of sun is low on the horizon, walk toward the sun and look a distance in front of you to look for the extremely translucent red carnelian agates.
Read on for lots more and definitely stop in the Gitchee Gumee Museum if you make it to Grand Marais! (done it, loved it!)