Dallane wrote: not a huge effort or give little gain. You will get tons of silver, gold and glass from what he showed while looking for blackrock and actively working the mine to help the drop down.
I disagree. Statistically, if you left more space between those tunnels, then for the same effort you would have more chances of finding interesting veins (silver, black rock). I think glass and gold are outside the subject of this discussion, because with those your mining strategy doesn't matter, only how much you mine.
If you leave more space between tunnels there is a chance you will miss some silver veins (because they can be so small). But the amount of tiles you check (that is mined tiles + 4 adjacent ones) is still the same (assuming you have mined up the same amount of tiles)