About 4 months ago my father had a particularly bad case of stones. So much so that he couldn't pass them; not because they were large, but very small.
Eventually he had to go in for minor surgery, where they went through his back into the kidney had sucked them out. When I visited the day after the surgery, the urologist showed me the stones in a vial and they looked like a teaspoon of golf course sand or granulated sugar.