Petoskey Stone Earrings, Lake Michigan Jewelry, Petoskey Stone Jewelry, Nature Inspired, Fossil Jewelry Petoskey stones hand picked from the shores of Northern Michigan, tumbled and lightly polished, hand drilled, hanging from sterling silver earwires. Stones are approximately 1/2 inch long. Petoskey stone is a rock and a fossil, often pebble- shaped, that is composed of a fossilized rugose coral, Hexagonaria percarinata. The 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. (Wikipedia)