Assuming that you are going to start mining from surface to underground, what is the most efficient mining pattern that guarantees the highest probabilities to find mineral? It would be nice to have a pattern that allow also to go back to the surface easily.
Like Joe, I also use the grid of vertical/horizontal tunnels techniques.
Horizontal shafts are 3 blocks tall with periodic dams to minimize flooding if I pop an underground lake. My horizontal shafts are roughly 300 - 400 ft apart (using the depth meter) and line up with where the background textures change (dirt -> rocky dirt -> all rock.)
Vertical shafts are 2 blocks wide with wooden platforms every 6 blocks up to act as a ladder. I space them apart by counting aloud between 10 to 15 seconds while running in the horizontal shafts.
Digging the tunnels takes a long time but it helps if you craft a good pick (demonite or better) and/or get some friends. Be careful about digging though the dungeon (skulls) and flooding your tunnels with the oceans on either edge of the map. The fire imps in the underworld also make tunneling a PITA. I suggest building your bottommost horizontal tunnel right above where they start spawning.
I guess this isn't really the most "efficient" pattern, bit it is thorough. And it's convenient once you have a highway to run from one side of the map to the other. I also have used it to flood hell, which was funny.
Piggybacking on what jaminja said on comment about map viewers, I can state the following:
- Ores are generally well distributed on the overworld, with exception of where the game spawned certain structures (i.e. the Corruption, the Dungeon).
- As you go lower, you will get more valuable/advanced ores (i.e. from copper to iron and gold)
- The jungle has an increased chance to spawn more ores than other biomes.
Eventually, if you dig straight down, you will reach a cavern. And due to the distribution of ores, creating a pattern such as the one showed by Joe can probably not be worthwhile. I say this because I've done something similar, to the whole map (although it was to eventually seal off the hard-mode map).
Making a pattern in the jungle is hard, mostly due to the presence of enemies and because the jungle has already several empty spaces.
The only place where I needed to make a pattern was in the Underworld, as the lava that comes from the Hellstone is cumbersome to deal with, alongside with the Fire Imps.
Taking advantage of the Imp's spawning algorithm, I design my Underworld mine with the following criteria:
- Horizontal corridors can't have more than 3 blocks height.
- Vertical corridors can't have more than 2 locks width.
- Rooms need to have some "hanging" blocks, such that the before mentioned is verified.
- Leave an ash border 1 block thick around Hellstone, as to contain the lava.
Having any sort of wide pattern is prejudicial when hard-mode ores come into play, as the spawning algorithm, instead of spawning a block of ore, replaces several blocks to the corresponding hard-mode ore. Also, since at that time you may have access to the ingredients needed to make Spelunker Potions, having a pattern is only helpful if it helps you reach lower levels.