I made a primitive stone ax. The stone was sharp for a long time. You need to cut the tree under a slope, otherwise the stone will quickly become blunt. The ax used to build a hut and as a weapon from wild animals for the first time. The ax lasted 3 weeks, cut down a bunch of branches, about 60-70 trees with a diameter of 5-10 cm and 2 trees with a diameter of 15-20, after the stone could not stand and broke.