Joxie just gave away the best lower level mine in the game, IMO. Not the one that has the bloodscalps, but the one that has the ravenclaw's in it, that is right above the dalaran wizards camp.
One note about mining. Nodes that are inside mines and nodes that are outside mines are set on differnet timers. Mines are considered "mini-dungeons." they have a higher concentration of baddies so the the nodes are set on a faster respawn rate. So if you find a mine that has 3-4 nodes in it, stick in the area. it will take some time, but these nodes will respawn faster than ones outside. So you can either A.) travel around trying to find more nodes or just hunker down, kill things and wait for them to respawn. When i was upping my mining level, I just camped out at a mine that was well below me, got up, did other things checking back ever few minutes (sometimes finding bodies around me from where my pet had saved me.) when the nodes respawned, I just went back in.
Also, gems are more likely to pop up in a mine than they are in an outside node.