@PaulaRocksmasher has a nice sound to it, eh?
From your brief video, there are 3 things to fix to give you success.
1) Your hammer has good weight, but the flat head won't break rocks very well. If you had layers, it would work well to separate them. What you need is some kind of point to concentrate the impact force to help break the rocks. Most rock hammers are smaller with sharp tips.
2) When you hit that large rock, watch closely as it bounced around. That bouncing took the initial impact force and transformed it into motion instead of cracking. You need to hit the rock on a stable and hard ground surface.
3) Take Harte's advice mentioned above. Even with your smaller female size, you can do this. With your new sharp hammer and rock on solid ground, grab your hammer, raise it fully above your head, grab the handle with your other hand, start screeching like a banshee, start bringing the hammer down with force, channel your anger that the rock isn't an arrowhead, screech even louder (scare away even the skunk apes), close to the rock the hammer handle should be near parallel to the ground, visualize yourself smashing through the rock and striking the ground below it. Take a deep relaxing breath and pull your hammer out of the ground and see what the rock gave up. Note that, if you do the procedure correctly, you'll vaporize the rock, so you should have eye and hearing protection.
You'll also find that you can get great exercise from rock smashing and continue your weight loss program. You might scare your cats, so make sure they're not very close.
To verify the calcium content of the rocks, you can pour a little vinegar on them. Unstable calcium (chalk) will foam up quickly, more stable less so. You might have a type of compacted coral.
