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The following article has been written whole or in part by Byron Buckeridge.

According to the Wisconsin Geological Survey, concretions originated 20,000 years ago in Glacial Lake, Duluth (now called Lake Superior.) They are made of clay, sand, and silt, and hardened with lime or iron oxide.   

Their “theory' is that concretions began to form around a fossil nucleus and the shapes are caused by (A) the number of nucleation ,  (B) bedding of the surroundings deposits,  and (C) , direction and rate of movement of mineralized underground water.

It is said by some that the Concretions were made by a Chippewa God who gave each one a little soul.

The Concretions are found in just a small area along Lake Superior. Very rare and no longer collectable.

They go from small round to large round then to many different shapes.   Below are a few samples.


Very few of the odd concretions are the same.  The round ones are very close.

Always be aware of where you are and ask permission to collect.
Come to the rock shop for more information and to see many fine specimens.