Hi Mucker,
There are huge differences between how Mining operations run and Mining Exploration operations run. My experience is that the mining side runs like any other (cost control focused) business with regard to HR activity so work schedules, holidays etc are well know and planned. Summer is just another season and a great one for holidays!
In exploration the situation is very different. Anybody that is line exploration staff (e.g. below the senior geologist level) is going to be in the field from late May to late August. You might be able to get a long weekend in there somewhere while mobilizing between projects but otherwise the field staff is in the field. The same holds true for drilling staff, air crews, and the various support services. When a project or area goes hot everyone works as much as they can.
As to more senior geological staff and office staff they seem to run their holidays like anyone else but typically when the ground is uncovered and not frozen there is more work then time so its all hands on board until the students head back to university. Then a quick break and back out until freeze up.
I am sure there are companies that do things differently but from my experience working in exploration with both juniors and majors that tends to be the norm on the exploration side.
... Been There