There are four kinds of ore:
- 1 yields 2 ingots
- 2 yield 1 ingot
- 1 yield .5 ingot
You get the later ones if you mine longer on a spot/until it is empty. You get twice as much ore if you mine in fel Dont forget that you are likely going to loose some higher quality ingots on smelting fails.
The difference between mining and lumbering is that most of the lumbering spots last only very few swings with your axe.