There's recently been a lot of controversy over what to do with those achievements, since depositing is no longer possible. But you can still mine them! Would it be a good solution to just change them to minerals mined?
Make the mineral deposit achievements count minerals harvested?
They will not be returning as achievable medals. We may get a better use for minerals down the road, so keep grabbing them!
yep, Hawksteel, with much fervor it has been suggested to change the wording in the achievement (or many other suggestions actually), but at this time they are deemed "obsolete" and they're not going back to make them achievable. OOO may, in the future, decide to delete specific (possibly all?) achievements from Steam, but still keep them in the game. For now, they're in hiding (the achieves... not OOO :D). The main thing having achievements connected to Steam is the 100% you see in your game library and on your profile page (if you have your achievements stats showing).
I'd direct you to briefly look through this thread for more answers: http://forums.spiralknights.com/en/node/97780#comment-881403. Thanks for your interest and I hope this helps!
already been suggested.
generic answer is: the idea is ok (but let's wait for the arcade redux).