A few questions about mining

[Zepar72]

Is ore / rock nodes quality related to depth of deposits, or is it always random? I know that node hardness goes up the deeper it is.
Another question, do natural cave galleries appear on all levels, or only on first ones? I've made it to -5lvl in my mine, and the only levels where i could find natural tunnels were -1, -2 and -3.

[Audiosmurf]

Is ore / rock nodes quality related to depth of deposits, or is it always random? I know that node hardness goes up the deeper it is.
Another question, do natural cave galleries appear on all levels, or only on first ones? I've made it to -5lvl in my mine, and the only levels where i could find natural tunnels were -1, -2 and -3.

Quality will, generally speaking, increase the deeper you go. Anecdotally, I remember seeing cave galleries appear as deep as level 5, but can't back that up with anything concrete.

[Tammer]

Some of your questions are answered in the world 10 announcement.
http://www.havenandhearth.com/forum/viewtopic.php?f=39&t=52822

I've seen l5 galleries in this world.