Metalurgy is the best way to get them yourself. The way to double>triple your efforts is to metal convert the unkowns/copers and make ingots/silver ore stacks. Sell the iron ingots to blacksmiths and the silver ores to people ranking refine along with any you get from metalurgy + sell gems. Then us that money to buy more diamonds. Doing this method for about 2 hours (not counting conversion times/re-selltimes) you should e able to get yourself 15-25 CM of diamonds.