Illegal loot, in the case of the ebony mines.
I'm expecting them to do it similar to Ultima Online, of course - in an ideal world. You take yer axe, you chop at a tree (and in UO's case, the tree doesn't bother to fall down because if it did the entire world would be deforested in a week), you get a log, and you use your dagger to turn the log into some arrow shafts and then attach feathers which you plucked from some bird that you killed, or use carpentry tools to turn it into a board, etc, then furniture, or a wooden shield, or whatever. Or you take a pickaxe and whack at a mountain for a while to get some ore, which you then smelt into iron, which you then forge into a weapon or a shield, etc, or tinker into some kind of tool. And all of this uses skill checks and requires a certain level of skill to make each item. Or you use your dagger on a tree to get kindling which you use to light a fire (using the camping skill) in order to cook raw meat or fish into something edible, although if your cooking skill sucked, you were liable to burn it instead. (Or keep a herd of sheep in your house to shear them for wool, and sell it for profit)
Seeing as they've cut back on the number of skills in Skyrim, I doubt they're adding a bunch of different crafting and resource-harvesting skills, along with camping, cooking, fishing, tracking, and so on, to make a really in-depth system. So it's probably more along the lines of Gothic II. Kill something, get raw meat, find an already existing cook pot over a fire which never goes out. Use cook pot to cook meat, and never fail. Take iron billets and make them into swords, and never fail, for unlimited profit, but first you have to become someone's apprentice. Etc.