My FIL worked for Solomon and Teslovich (might not be spelled correctly ), just outside Uniontown, Pa. ( till he retired 32 yrs ago. and was in the Operating Engineers local.Mackford13
Looked like foundry or frac sand. I've hauled many loads of them in pneumatic tankers.
I use to be a greaser for the Operating Engineers. I should of stayed with it and been an operator, but decided to continue trucking.
I have hours on a Cat 330, Kobelco 350 & Komatsu ? can't remember the model and always liked running excavators, but I basically just played with them. I don't know if I could do it every day.