When we lived in Illinois and were a rockhound, the Soo Line railroad would haul carloads of Taconite pellets to the U.S. Steel South Works in Gary, Indiana.
Sometimes those hopper cars would leak out the pellets along the rail road tracks and we would go up there and pick them up. They would wrap a few in a slip of newspaper and put a few other small crystals wrapped in similar fashion with four items in a paper lunch sack to be sold as Grab Bags and the mineral shows.
Fluorite was used as a Flux in the making of steel.
It is very long time now since I have been involved in any of that since I sold my collection before I moved out of Illinois. ;)