This image shows the unexpected fate of a large quantity of grind stones which had been manufactured nearby but found no owners. They are used for shoreline stabilization for which they are also eminently suitable, given their great size and hardness.
The L.L. Cook Co., Milwaukee, WI
The description states:
2085 MICHIGAN THUMB SCENERY
Abandoned grindstones, once a thriving industry at Grindstone City, Michigan.
—Grindstone City is an unincorporated community at the eastern end of Port Austin Township, located at the northern tip of the ‘thumb’ of the Michigan peninsula. The shore shown here is part of Lake Huron.
This postcard is dated 1955.
Are there still grindstones that can be picked up there?
According to this article from last year, there are still large grindstones on the beach which you could claim:
https://thumbwind.com/2021/04/12/history-grindstone-city/#h-finding-grindstones-today
Some stones are visible on Google Maps. They appear to be on the beach behind people’s houses, so they may be considered “owned” already. A visit to the town before arranging to pick one up would be wise.
Since they weigh a ton or more, you’ll need some serious hauling vehicle, lifting equipment and assistance.