How does the 'Excavator' skill work?

[Dwagonsnare]

I was just working on grinding through some random eggs I had obtained when I ended up hatching a Black Stag with the 'Excavator' skill. It says this skill is supposed to allow it to help me gather resources, so I decided to keep it.
When I go to mine (stone, pyrite, etc...) I am given the option to send my beetle to help. The beetle then walks up to it, starts a 'mining animation' where it opens and slams it's jaws together repeatedly. If I walk in front of it during this animation I take damage (or at least I would if friendly-fire was turned on). Eventually however, the animation ends and the item the beetle was mining, remains completely unaffected?
If I try to help while it's mining, it doesn't seem to drop any extra material or anything. How is this process supposed to work?

[Cuchilain]

Is the mineral in the beetles personal inventory?
So it would be as if you could mine it twice?
I need an answer to this because it sounds important.