I assume this is either a bug or lack of balancing. Otherwise I can't explain why the differences between mining different resources are so big.
As stample mentioned, there is indeed extra heat added that is linked to sound. I remember faatal mentioning that back in early A18 when they were trying to locate the bug that was causing mass amounts of screamers. A single torch would call in a screamer every 1 hour and 40 minutes of real time. Candles were messed up too.
When they were fixing things up, faatal did fix an issue with the auger, but just with the startup sound:
Unfortunately, I am having a hard time locating the post where the metal hit sound is mentioned. It might be in one of the posts that were lost in the recent forum migration.
However, in general, madmole "answered" your question as to why the difference is so big:
But yeah, I agree, some balancing would be nice. In my opinion, it's ok with a pickaxe... and of course, I would expect it to happen quicker with an auger... but it's too quick with an auger. Since the heat is linked to the sound, in order to ease up on it for the auger, they would have to create another sound object representing auger on metal... even if it uses the same clip.
