The Gold mines in the game are useless for the amount of troops needed, the time it takes, and the paltry amount of gain obtained for the trouble....that being said, great Gold Mines are insulting as a win in KVK's....for the amount of time, effort, and $$$'s put in as a reward. No one uses them usually unless there are no other yields open and they're logging out for 15+ hours or so...and they need 1000 or less gold that bad, which at higher levels is basically useless amount of gold also. 

BUT, one change could actually turn a useless reward into a useful addition to the game and make ALL your player base happy. 

If you added a chance for a yield from ALL Gold Mines giving you a chance for Platinum or Grants.

And a chance on a Great Gold Mine to have a chance for Platinum, Grants, Sulphurum, Empire Ingots and Hero Crystals.

Any yields have a CHANCE but a payout for a clearing will gaurantee at least something,,,

This small change would help ALL your player base and make them extremely happy I am certain. The gold mines are truly worthless, and the lower level ones which are even longer times for even less gold are just painful, hope y'all give my idea some consideration