"Tangential aside - is this a thing? A hobby? Research? Paid employment?"

All of the above and more. I'm invested in it enough that I'm going to become Vice President for California's oldest mineralogical society next year, most likely.

"I've not heard about digging up minerals for fun."

You've never gone rockhounding or had some sort of rock collection when you were a child?

I vaguely remember having a rock with some sort of purple crystal formation, probably bought from the gift shop of a show cave, but I've never come across that as a hobby before. I guess I never really thought it through - they have to come from somewhere, after all!

I've already got a lot of outdoor hobbies - underwater archaeology, caving, and recently took up cave-diving - so it's interesting to hear about something related. Thanks!