You may enter the mining guild once you have a mining level of 60. Inside you will find more than 20 coal rocks and 3 Mithril rocks. There are two entrances to this guild, one through the building right behind Falador bank, and another in back of the Dwarven Mines by the coal rocks. If you are level 59 and wish to enter, you can drink a Dwarven stout to boost your mining level by one, but it will wear off.