Petoskey stone

My photo is unedited. I held the camera at a distance of two inches.

Petoskey stone is found in the Great Lakes, mainly along the lake shore in Michigan's Lower Peninsula.

WIKIPEDIA: A Petoskey stone is a rock and a fossil, often pebble-shaped, that is composed of a fossilized rugose coral, Hexagonaria percarinata. They are fragments of a coral reef that was originally deposited during the Devonian period. Such stones were formed as a result of glaciation, in which sheets of ice plucked stones from the bedrock, grinding off their rough edges and depositing them in the northwestern (and some in the northeastern) portion of Michigan's lower peninsula. In those same areas of Michigan, complete fossilized coral colony heads can be found in the source rocks for the Petoskey stones.