Try hitting the rock again from the opposite direction lol jk.
I'd try a hammer as well, I've used a hammer and steel weightlifting weights to massage a few in the past.
I was starting to think it was
Bill F**King Hitlery, wearing BigFoot Hair, Ewww!!! while Biting Frog Heads, and acting like
Bombastic French Hedonists. Where does it end I sometimes wonder?