While nothing can compete with open-cut for the sheer size of the operation, the continuous miners used underground are by far the meanest machines in the industry.
This first image shows the machine as it's supposed to be. Dirty and at work.
By the looks of the operator cage on the right it seems this one's an older sit-on model as opposed to the now industry standard remote operated design.
This next image is the CAT CM445 continuous miner, clean and shiny on the workshop floor.
Finally we have a similar machine, the JOY 14CM at work underground.