Quotes from Captain Ahab;

I know not all that may be coming, but be it what it will, I’ll go to it laughing.

All my means are sane, my motive and my object mad.

Well, Captain, so the MoFo Moby Chert Whale is growing on you! 

I'm sorry, I can't type while I'm chuckling so hard, but I kind of thought this might be the case. I'm just very glad you did not get hurt in the process. That rock is some serious sharp stuff!

So, if you tell someone that has done some flint knapping that there is an ART to busting rock, they will know what you mean. But if you tell someone that has never done any knapping they won't have a clue what you mean. But, YES, there is an ART to it! Even with a 20 lb sledge.
If you just start beating on a rock and hope that it breaks, then you will pulverize it into little chips, shards, and powder. You have to plan how to reduce that rock. The force of your blow is to knock a piece off the side. Shear it. Dig all around the rock and find weak spots. Empty voids and cracks that you can try and use as a break away spot at the end of the crack you are going to make with a blow from your hammer. It ain't rocket science but it does take some figuring, and there's a whole lot more to it than just beating on rock with a hammer.
Now that you have discovered that Moby is actually just the top of the chert bedrock peeking out, you may decide to move on to greener pastures. But, you have dug a good opening. There are hollow areas all thru the chert bedrock. If you dig all around that outcrop you may find a way to pursue reduction. But instead of trying to "break the rock", try knocking a 6" wide piece off the outer edge, and maybe work your way in that way. You want the force of your blow to cleave a piece off, rather than send a crack through the whole thing.
It's too dang hot now anyway!
Be careful down there, and thanks for the pics!

" By the calendar I'm in my 60's, my brain thinks I'm in my 20's, and my body thinks I'm 80. Can't play in those temps like I used to."

That's it in a nutshell, my friend.