2,207 bytes added,
18:05, 7 July 2013 ===Prospecting guide (large rock face)===
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+---+---+---+---+---+---+---+
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| | | | o | | | |
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| | | | 3 | 2 | 1 |<--| X |
+---+---+---+---+---+---+---+---+
X = no prospect of that ore
<-- = last tile you did get a prospect
3 = I recommend you start mining here
</pre>
Realize that the world is two-dimensional. All the rock and ore tiles are pillars, they are not cubes. You can ignore the height of mountains when prospecting. Only North/South/West/East matter.
When you prospect on the surface, you can detect ore in an area of 7x7 area around you. That's 3 tiles in all directions from the tile you are prospecting. Prospecting inside a cave is not done to find ores, but to tell specific details about the tile you are prospecting.
When you prospect e.g. iron ore on the surface, that means that somewhere within a range of 3 tiles around you (including the tiles behind you) an iron vein is located. You then try to find the tiles where you can no longer prospect the ore. You need to find one North or South edge, and one East or West edge.
Then count 3 tiles from both those edges and the tile you end up with is the ore vein.
You cannot mine the vein tile directly from the surface. If you try to mine the vein tile from the surface, you will get the message <b>You fail to produce anything, the rock is stone hard</b>, or <b>You cannot keep mining here, the rock is unusually hard</b> (only when you were supposed to get a stone shard, otherwise you'll get <b>You chip away at the rock</b> as usual). You will have to start tunneling in the tile next to vein.
Sometimes grass, dirt or other tile types hinder the prospecting. Try to find a large rockface to ease prospecting.
Or you can try this program out as well: http://discon.googlepages.com/prospector.html
Alternative Web tool: http://www.pvv.org/~magnusrk/wurm/prospect.html