Here in Grand Rapids, gypsum used to be mined. That was played out long ago, but that temperature stability you mentioned has proved an asset for longterm storage of important documents and whatnot, for various businesses.
“Grand Rapids”
I don’t get all the way to Michigan very often, but just drove through Grand Rapids, on my way to Muskegon.
Delightful weather today, beautiful state.
Will relax near Macanaw City next week.
;-)