This is a rather simple way of making gold with jewelcrafting but it can be very effective and you can make thousands of quick gold doing this. Basically you will want a lot of stacks of Ghost Iron Ore. You can either buy a ton of it or you can go out and farm it if you have mining.
When you have all the Ghost Iron Ore you want, you will want to prospect it into gems. For this you can make a macro that looks like this:
/use Ghost Iron Ore
and it will make it a little easier for you. Once you have prospected it all, you have two choices. You can either just sell the gems or cut them. Usually just selling them is best and you will make a big profit.