Additional Rules from the Rulebook
Generally, you can trash a Copper card and gain a Silver, or trash a Silver card and gain a Gold. However, you could also trash a Treasure to gain the same Treasure or a cheaper one. The gained card goes in your hand; thus, you can spend it the same turn. If you don't have a Treasure card in your hand to trash, you can’t gain anything.
The Secret History of Mine
In an article on Board Game Geek, Donald X. Vaccarino commented on the development of Mine:
- Of the 10 Actions in the first game ever of Dominion, this has changed the least. It always cost 5, and always let you trade Copper for Silver or Silver for Gold. The only difference is that now it phrases this as "gain a Treasure costing up to 3 more," as if someday there might be other treasures that this would also work with.