It does tell you that. For example, a level 20 iron mine states specifically that it produces 960/60seconds (ie every minute the mine makes 960 units of iron) whereas the same level copper mine states that it produces 1440/60seconds. The capacity for each resource is also specifically stated, with copper being higher than the other resources. You can increase the capacity through techs but the copper capacity is always higher.
Looking at lower level mines to give you an idea a level 1 copper mine states that production is 72/60secs where as the iron mine is 48/60secs. These figures (adjusted for level of course) are clearly stated within your mine when you click on them.