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[R Saunders]

Lightning Stones
These are Septarian Nodules locally called Lightning Stones. They are found on beaches in the lower west side of MI. These were found in South Haven, MI. They consist of clay cemented onto an iron mineral called siderite. These concretions form in part through bacterial activity. They become fractured and the fractures fill with calcite brought in by ground water. The results forms lightning like patterns on a dark background.

I have ground and worked the large one at the top right.