I believe there is around about 4 rocks I haven't been there for a while.
Well it differs over time but easy way is to go to the grand exchange and check
You should mine like in the desert mining area for mithril ore or iron ore. I myself am a mining fan and always tell people that you should go to the desert but get your mining to 60 so you can go to the mining guild. it's so much better!
Mithril Ore is currently 488gp ( Market Price ) in the Grand Exchange.
from grand exchange ~1.6k
The current market price is 58 gp per arrow.
30 each
You can buy a Mithril Pickaxe from Nurmof's Pickaxe Shop in the Dwarven Mine, but beware of the much more expensive price offered by the shop. You can also buy it off of the Grand Exchange for the best price in RuneScape shops. It's also possible to obtain a Mithril Pickaxe from monster drops from Living Rock Protectors, Dagannoth Rex, and Living Rock Strikers.
You get 50 mining experience for every coal you mine.
Probably not that much, your better off selling them to general store, or Ranged Guild ( If you can get in there ) for a little more cash then general.
You cant buy them, they must be won in the minigame The Great Orb Project, found in the runecrafting guild.
You could be looking at around 140k Per hour.
try goin on to a website called sals realm of runescape and look for skill calculators thats what i did on all my skills
Level 85. It isn't really important: at that level you can make money about as fast mining clay, than mining rune ore. The rune ore is worth a lot, but it also takes much longer to get.