RLS- how about a shot of 'down the blade' of your 'chopper'... You may have something, tho it may just be a rock cracked open from falling or being crashed into by another rock... W/ the pics you offer, I'm inclined to think the former. I could very well be wrong. Give us another shot of that rock- Yakker
Could be a grinder, looks close to the type of stone they used here. Your pics are kind of blurry. The last pic looks worn. Those type of things are hard to see. Its probably something you will have to decide on your own. If it has a worn side with a dimple Id have to say yes. It depends on where you found it also.
Rock, I believe you are right,it is a grinder,bottom is smooth as a baby's butt,back end is square to the bottom and has two shallow dimples,the is a depression on right side the fits two fingers perfectly to hold when grinding.pointed end has damage similar to hammerstones also. Found in Tennessee...thanks for your help Carl