at first glance look kinda natural to me- are the interior of the cups smooth? In my (little) experience the natural cups tend to be really smooth to touch. Also, they look kinda irregular in shape- you would expect grinding to produce a fairly even circular shape. We had a thread on here a couple of months ago re natural vs man-made and I've come across both on the same stone, so it's possible they could be worked/extended natural cups.