Petoskey kernel earrings. Measures at about 25mm long Looped Ear wires. Each pair with 5 kernels and accented with two 4mm sterling silver beads. Lever-back ear wires. Petoskey Stone This interesting stone is a variety of Calcite. It was formed by the fossilization of ancient coral, Hexagonaria. The coral lived in shallow waters and today's fossil often includes ancient silt and mud. Petoskey Stones are found on many beaches of Lake Michigan and Lake Huron, as well as in rock quarries from Travers City to Alpena. The honeycomb patterned stone has a hardness from 4 to 5 and is the official Michigan State Stone.