Bipolar Percussion 

the anvil stone needs to be flat i do bipolar purcussion all the time because my local chert thamy people use/used is rounded by the ocean in santacruz california so use a flat anvil stone and a pestle shaped hammer stone

and i c the stone is flat the cobnle will not slip as much

You explained what is going on here, I'm in the San luiz valley, I find the split pebbles, I have arrowheads, made from split stones, I have stones that blew up while this was done to them. And I have the hammer stone they used, I'm going to dig for the anvil. I have found arrowheads, all over america. But I have never found the archaic artifacts I have found here? Another strange thing, is they used chips, but They struck the chip in such a way, as to make a flake a one sided point, that has three little triangles parts to them. Hard to explain. But I also find Black Jasper, that was the shape they wanted without knapping it. But one edge will be sharpened? They litterly used whatever they picked up out here, And what is here is small stones only. Good material like obsidian, brecceatted jasper, Very pretty stuff mostly, like they knew it was special? The reason I am finding all this stuff, is 2 years ago, The landowners, sold water rights. So wetlands that have beenb estuaries for migratory birds for millenia, are now dry. They sold the water that used to flood this area, for miles. SO What seems a harsh lifestyle, was pretty good.

Sorry have to roll my post up, won't read more.

Amble stone? I think you mean anvil.

@@bracoop2 yes, indeed. Thanks for noticing. I have corrected the typos. Anvils!