Mining is used to harvest metal ore from mountains and smelt ore into ingots.
Raising Mining: Mining is a resource gathering skill. Double click a shovel or pickaxe and target a mountain for a chance to harvest ore. Do this repeatedly until you reach 100 skill. Higher skill will allow you to harvest and smelt higher quality ore types:
Iron, Dull Copper, Copper, Shadow, Bronze, Gold, Agapite, Verite, Valorite
Gideon's Advice: Develop a path you follow while mining so that you reach a forge right when it's becoming a burden to hop the ore further. Using a pack horse can also be helpful and creating a macro with Razor is a must (mining by relative location is very helpful). I usually make a path where there's a forge at the halfway point and at the end. By the time I reached the end, the beginning ore was respawning. Also, I find that waiting to smelt iron ore until you won't fail will increase your profits. If, however, you want to gain faster, smelting ore 1 by 1 will give you good gains (again, use a macro). Tinkering to make your own shovels as you're mining is an effective way to raise both skills and minimizes the weight of shovels on your character. However, shovels are actually quite cheap at the vendor (npc tinker).