Start the process with a thin piece of soft mineral, such as obsidian or flint. The stone should be 1/2-inch to 3/4-inches thick. The stone should be no larger than the palm of a man's hand.
Draw a pencil line lengthwise, down the center line of the soft stone on each side, then draw an outline of the finished tool around the perimeter of the stone. You will use these lines as guides as you shape the rock into an axe head.
Strike the harder stone with the hammer and brick chisel, and break it to expose a sharp edge of the harder stone. You will use the sharp broken edge of the harder stone to shape the softer one.
Strike the soft stone with a sharp edge of the harder stone. Strike it in such as way that you chip away at the outer edge of the stone and shave it down into a sharpened edge. If the soft stone was a piece of soft wood, you could simply whittle the wood away with a pocket knife. But because you are working with the same tools prehistoric men used, you have to strike the rocks together to shape the softer one.
Visualize the finished project as you shape the soft stone. The finished quadrifacial axe is shaped like a large arrowhead, comes to a rounded point at the front and has a sharpened edge around three sides.
Continue shaping the soft stone by striking it along the face until the stone is the proper shape. Then, turn the stone over and use the harder stone to sharpen the edge of the axe head. You will remove a small amount of the softer stone with each blow and slowly create a sharp, cutting edge.