I know Flint and Obsidian can get to the single atom as far as sharp.
And that the best steel blades are a whole lot thicker they are still sharp.
There are ceramic knives that are sharp and stay sharp for a long period of time but they are fragile.
There is a reason the Flint knives we find from prehistoric times that are 2-3" at longest and about 1-2 as normal is they are very fragile and longer blades when dropped, hit bone, or are struck on hard objects they broke.
The huge Flint spear heads you see in pictures like on the cover books, magizine articles, and others are artistic license.
I had two of the ceramic kitchen knives and boy were they sharp, they made fast work of meats and vegtable mater.
But you drop it once or hit a bone and any lateral movement snaps the blade, and you have a handle with a really sharp nub. before that I thought a smaller one would make a great as a field knife especally the smaller one I had but it droped and broke and the larger kitchen knife I was using to carve a bone in Roast, it sailed through the meat and when I hit the back bone it went through the connective tissue but that little flick of a wrist you do to get through the bone snapped the blade.
