Second solution: Keep only one form of essence, but swarm the essence mine with (for example) level 49 aggressive monsters with range and mage capabilities. Just flood the whole mine so that it is only appealing to mine rune essence upon reaching 50 combat. Or if you split up the forms of essence, do this for the pure essence mines, which will not hinder lower levels from mining the basic essence. It would be imperative that the monsters were highly abundant and could not block each other, to ensure no macroer can find himself a safe spot to mine. It would also help to make the area multi combat, and give these creatures a very fast respawn time. That solution is kinda bad because sure I have like 600 skill toltal but my account is a levil 51 pure mage.... The only way to defend myself will be using runes so all my profit from mining will go to waist...