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We all love our knives. Each of us owns several of them for various purposes and they’re the most indispensable tools that we carry. So the idea of making a stone knife may seem primitive and even backwards, but what happens if you get caught without a knife? Or you need to do some butchering work and want to keep clean the only knife you have on you? A sharp stone knife can fill in for your favorite knife, and the best part is that they are easy to make.
Most parts of the globe have abundant rocks that can serve as blades, and you don’t need to be a geologist to find them. Razor-edged rocks are as close by as the nearest creek, although not all rocks break with a good cutting edge. Flint, chert, jasper, chalcedony, quartz, and obsidian are a few that do. Try the different types of rock in your area to see what works best. There are two ways to get sharp flakes of rock for your stone knife and other tools–bi-polar percussion and direct percussion–and both methods involve striking the stone with a hard hammer rock. For either method, I suggest you wear gloves–preferably made of leather–and protective glasses of some sort.
With bi-polar percussion, set the rock you are trying to break on a large stone, which will act as an anvil and provide unyielding resistance behind the rock you want to break. Stand the rock you want broken on its tallest axis. This allows the shock waves from the strike of the hammer stone to move through the rock on the most efficient path. Use a large, flat hammer stone to crack down hard on the rock you are breaking. The hammer rock should be 4- to 5-times larger than the rock you are breaking. If you are lucky, you’ll fracture off some nice, thin, wickedly sharp stone blades with a few strikes.
For direct percussion, we take the anvil out of the equation. Select a piece of rock about the size of a sandwich in thickness and width. This will be the rock you break for blades. Select another rock that’s round and a little bigger than a large egg. This round stone will be your hammer. Hit the thinnest edge of the “sandwich” rock with your hammer stone. Hit it hard–right on the edge–and follow through with the strike, kind of like driving a nail with a hammer. If you picked a good rock, and hit it hard, you should have knocked a flake of stone from the underside of the rock, which will be your cutting or scraping tool.