This is a very important skill for anyone wanting to place an endless copper mine. Once a mine is found that has copper that can be mined faster, you will be able to keep this bonus when you place the endless copper mine. It's still not a bad skill to have even without the endless copper mines. Fast mines get ore out in half the time as a normal mine. So where a regular copper mine would take 3 minutes a mine found with this skill active would only take 1.5 minutes. In essence your level 5 endless copper mine would act as if it were a level 10. Now imagine that buffed