cloud rose
I just thought it was a little strange that each mine has only one type of ore. It's like once you enter a new mine, the other ores just cease to exist. It would be great to keep the types of ore from the previous mines when you unlock a new one.
For example, in the water mine where you find silver ore, you could also still find bronze ore nodes that you found in the earth mine (albeit at a lower rate than the newly unlocked ore). In the wind mine, you could also find bronze and silver ore in addition to gold, etc.