[FROM: Helgard Frey]
I arrived at scandinavia, and caused by this I'm still wondering wether it might be better to unlock the scandinavian repeatable mines or to stay at the egyptian ones. Therfor I think it would be great to expand the wiki's list about repeatable Mines and add how much materials you'll find there :-) I know it depends, e.g. in abandoned tunnel, sometimes you get 20 and sometimes 21 lumber - but it could be the average number... :-) in that way you could calculate wether it's worth to unlock the scandinavian ones ;-)
It's worth opening the mines except for the iron one. You get more per day, although energy effectivity is mostly lower.
For iron, you get around the same amount of ore for twice as much energy. At least the one time I digged it. Possibly the other variants may be better.
Anyway, except for lumber and stone I'm not doing other repeatable mines, since the hard rock cavern will give you 2-3 times more of remaining resources then dedicated mines and amethyst is invaluable since the items you can buy for those are extra class.
Here my observation:
lumber: varies too much
stone: 1-2 per 30 energy tile, 4-7 per energy tile
copper: 1-2 per 40 energy tile
coal: 1-2 per 18 energy tile; 2 per 30 energy tile
tin: 1 per 50 energy tile
iron: 1 per 60 energy tile
thanks Peter for your answer - i think it'll help me a lot! :-)