At skill level 3, one can obtain Pieces of Coal through Mining. One also has a considerably rare chance (1 black ferrite for every 36 ferrite) to obtain Black Ferrite through Mining. At skill level 4, you will at very rare times extract Crystals. Crystals seem to be 1% or less of the yield. The higher one's Mining skill level is, the higher chance they have of successfully obtaining Ferrite as well as the other less common items.
One can use a Coal Axe instead of a Mining Axe while Mining. When using the Coal Axe, one only obtains Pieces of Coal. However, a Coal Axe will break quickly when being used unless one has a higher Mining skill level. A mining axe may randomly break.
An Imperfect Ferrite is sometimes mined, there is no know use for this item.
A tip for those in Lerilin who want to go Mining: follow the path west from Lerilin, out of the main gate. This path will pass a few different rock formations, the first being just outside the gate, the second being near the fork to Brigobaen, and third being at the bridge. This area is almost completely clear of beasts. Note that if you cross the bridge, things start to become more dangerous.
Many players mine the huge rock formation southwest of Lerilin, but as this contains the Ant Cave, hostile Forager Ants often surround it. At the southwestern tip, even Green Sludge Beasts will appear. The occasional Bracken has been known to show too. If you are Mining in that area, be prepared to fight, or possibly run.