Need help identifying these rocks please?

[RockofAges]

I found them on one of the shores of the Michigan's Great Lakes (think it was Lake Superior). Based on my research, i think they are called lightning stones, but not sure. If I am wrong, please correct me.. Next, based on the picture, what rock/minerals are they composed of please? ty

 

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[BurntBear]

Yup, that's a Lightning Stone or Septarian Nodule. They are clay-cemented over Siderite and the white veins are Calcite.

 

[RockofAges]

ty for the help