Okay so do we have:
1. an 'infinite pool of magic in the world' that can only be accessed by owning gemstones of a certain kind?
2. an 'infinite pool of magic in the world' that can only be accessed by excessive wizard-like training OR gemstones of a certain kind?
3. an 'infinite pool of magic in the world' and any Tom Deacon-Harry can become the next Dark Lord if he has a really big vault of magic coins?

It really messes with how magic and your economy works depending on which one you choose.
Oh and when I said hoarding, I meant good old "Scrooge McDuck" or "Red Dragon of Coin Pile" kind of hoarding where nobody at all is ever, ever allowed to have any of them and people kill each other just to get the coins. That sort of thing doesn't quite lead to inflation of the coin's own value, paticularly since in this technological age the value of the coins is the material contained within them.