If, however, you forgot to pack a knife, you can craft one from a stone. Although it is possible to make a blade from various rocks, including “flint, chert, jasper, chalcedony, and quartz”, Tim MacWelch prefers obsidian (pictured), a type of volcanic glass found everywhere near volcanoes.
If possible, wear gloves and goggles to protect yourself. Next, choose a piece of rock the size of a small melon with a flat or concave side. This is the stone you will break into blades. Then choose another stone that is round and a little bigger than a large egg. This stone will serve as your hammer. Then, strike the edge of the stone which will become a “blade” with your stone serving as your “hammer” from inside the flat or concave side.
Look at this video from Dr. Bill Schindler on how to make stone survival tools.