I may have a high tolerance for strangers but getting back to the hotel and hiding by myself in a perfectly clean room is a major part of my enjoyment of traveling. 😁
I am not sure about the mine, chalk or sandstone gravel were both options.
Turns out it is Aggregates, so basically gravel-
https://www.franklinwi.gov/display/router.aspx?docid=10238&
Thank you!