oddly enough the fact that you are finding so many of the same shape made from the same material is a dead give away that they are natural. your creek (creeks) in your area is producing, from a like stone, a similar shape that this kind of stone "likes" to be tumbled into. Ergonomics too, is a real red flag. It takes a LOT of effort to peck and grind even such small items. Most important, what do you see your tools being used for? Is there a better design for that use and a better material to use? ...perhaps bone or wood?