I had a stone pickaxe. I placed it in the enchantment table, however i didn't enchant it, i only looked at the enchantments. After an unknown amount of time, i placed a diamond pickaxe in the enchantment table, and the enchantments were different. Then i placed in the stone pickaxe, and there were again the stone pickaxes enchantments. After investigating, i found out that all of the pickaxes had the same enchantments, except the stone one. After enchanting an iron pickaxe, all of the enchantments were the same on all pickaxes. Please note that all of the other enchantments not shown in the images were all different. Note, this had previously happened work swords as well.