Petoskey stones are small water worn stones from Michigan. They are a petrified/fossilized calcium replacement of a variety of coral, Hexagonaria percarinata Sloss, and the state stone for Michigan. The blue/gray to tan colored stones have a very interesting pattern when oriented properly during sawing or grinding. This is a soft material which can be used for specialized tumbling, carving or slab for unique cabochons. Note the beautiful Petoskey stone cabochon shown in the picture to the left. Special procedures are required for tumble polishing Petoskey due to their hardness of around 3 on the Mohs scale. Kathy Miling of Michigan has a polishing technique that is superb! Thank you Kathy for sharing your lapidary techniques for success! Check out the link below. Sizes of the Petoskey stones are small and will run approximately 3 to a one pound order. One order is one pound of Petoskey Stone. When you receive your Petoskey Stone, wet the stone to see the interesting pattern. Stock 607F.