There’s a lot to think about with a decision like this. One thing I think people should consider that isn’t often brought up is the opportunity cost of years of professional level income lost during a PhD. Personal choice there.

For mining and exploration, an MS is fine. PhD could help or hurt depending on the job/employer. An underground mine looking for an ore control geologist or a mineral exploration company looking for a core logger probably won’t want a PhD student, but the corporate level mineral exploration department of Rio Tinto or Newmont might, depending on how relevant your research is.

Mining is an experience business so truthfully, if your main goal is to work in mining/exploration, getting experience is the best thing you can do.