If you go into the feed the beast folder and look at the configs for thermal expansion (in a folder called cofh) it tells you where they spawn, from mine it says copper at 40-75 and tin at 20-55
If you go into the feed the beast folder and look at the configs for thermal expansion (in a folder called cofh) it tells you where they spawn, from mine it says copper at 40-75 and tin at 20-55