Gruly's WoW Profession Guide| More on Mining.

In WoW, there are thousands of mine deposits. You will mine as you level up. From level 1-10 areas to lvl 60-70 areas there are mines. You will come across them throughout yours many adventures. You can mine anything that is grey, green, yellow, or orange. If the mine is red you cannot mine it. For every mine you will get 1 ore. You can mine it once and obtain a level. After that you can mine it a few times after, but you will not recieve a level. You can also get stones and jewels in a mine. Jewels are rare in a mine and you won't recieve them often, but stones are quite common and can be used for other professions. These are all the types of ores in WoW and the level required to mine, or smelt them.
Copper- level 1.
Tin- level 65.
Incendicite-level 65.
Bronze-level 65.
Silver-level 75.
Lesser Bloodstone-level 75.
Iron-level 125.
Indurium-level 150.
Gold-level 155.
Steel-level 165.
Mithril-level 175.
Dark Iron-level 230.
Truesilver-level 230.
Small Thorium-level 250.
Rich Thorium-level 275.
Fel Iron-level 300-330.
Raging Colossus-level 315.
Adamantite-level 355-375.
Thats more information on WoW Professions Mining