Delamore wrote:How can you possibly balance this so it keeps gold mines valued?
Gold mines are stuck in one location, finding them is hard and they are rare.
Gold is a bitch to smelt down too.
Ok now we have your idea:
Balanced by being hard to work out the first time
hard to get materials
So what happens when people know how to make it and the hard to find out thing is ignored, will it be hard enough to make to make it balanced against mining?
Then if it's hard enough to make even without working it out, why would it be worth it to try to work it out when it's clear that the effort to get gold otherwise is easier?
Well, part of the convenience of the stone is in his secretness, meaning that if the formula is unknown, you can get some of the materials with relative easiness (they could have some other uses, so you can simply bluff when acquiring them).
If the formula isn't secret anymore, it loses part of his utility. In that case, it could be easier to simply buy gold. But at least you have a difficult but possible alternative.
The point of this idea is to give an alternative source, but it isn't meant to be a replacement. It is supposed to be useful when the formula is hidden, and it is right if it loses part of the usefulness when the formula is revealed.
Of course, as more items are added, the numbers of combinations between items increases, and so the difficulty on gaining the right formula.