Parking Lot Gravel

Oftentimes, if one were to pay attention even a little, then small rocks can be found in any parking lot, whether it's paved with asphalt or cement. Exactly where these rocks come from and what type of stone they are isn't important enough to warrant research.
The rocks are small enough that they can't even be used for anything, though they can definitely get stuck in between the treading in your shoes or somehow end up inside them, being annoying.