Identify each kind of mines

Lately, I got more Titanium and Saltpeter mines. When they are depleted, I have trouble to tell if those mines are Titanium or Saltpeter in order to send explorers to find the new ones. So, I would like either:

- Add more names to the exhausted mines; for example, "Exhausted Titanium Mine". We already have "Exhausted Granite Pit", "Exhausted Marble Quarry", and "Exhausted Quarry", so just like those.

- Or give each mine (and exhausted) an unique color. We can use the colors of their icons (Copper, Iron, Gold). However, both icons of Titanium and Saltpeter are silver, so one of the two mines may have a different color.

Damn me, yesterday, I sent explorers to find a Titanium mines twice, didn't find it, thought it a bug, only found out it's actually a depleted Saltpeter mine. I feel so stupid.

not a biggie for me, but if the precedent has been set with other types of mines then surely this should already be in place