Once you find a Petoskey stone, one of the most popular ways to enjoy it is by polishing it. Polishing makes Petoskey stone’s distinctive patterning much more apparent, bringing out contrast and definition within the shapes without the need to wet your specimens.
Most rock and mineral polishing is done with lapidary equipment, such as diamond-bearing grinders and tumblers, but because it’s made of limestone, Petoskey stone doesn’t require expensive equipment to shape and polish it. And unlike other relatively soft materials, which often don’t take a good polish and look somewhat dull, limestone’s calcite-dominant composition and relatively densely packed grains enable it to take a fine polish. This makes polished Petoskey stone specimens perennially popular.
A common pebble before polishing (left) and after (right). Note the crack-like structure that was made visible by polishing. This was where the stone was once broken long ago but has since been filled by quartz that crystallized, thereby “healing” the stone back together.
This specimen, from a rock dealer’s “junk bin,” actually had a lot of detail to show off once it was polished. (Rough left, polished right)
