The chisel gives a 2% chance of receiving an additional gem of the type that are cut while using the chisel, but it only applies to sapphire, emerald, ruby, diamond and dragonstone. The chisel will consume 3.57% charge or 1.78% while in Prifddinas per gem created, so it will create 28 or 56 gems before reverting back to a crystal tool seed. If there is no room in the inventory for the extra gem, it will be sent to the bank. The tool seed can be recharged by Ilfeen, Eluned, Islwyn or Rhodri Dail for a cost that starts at 7,500 coins but decreases by 1,500 every enchant, to a minimum of 1,500 coins.