Ann: Quarterly Activities/Appendix 5B Cash Flow Report, page-8

In the 1920's there were just under 200 operating potash mines just in germany..... these old brownfield mines aren't unique... now consider greater europe.

Many of could be restarted with similar capex and economics of this deposit imo but they aren't for that very reason because more MoP isnt really needed and is in plentiful supply. Unless you have a yuuge advantage ie no shaft or very small power / big logistical advantage cost its going to be very hard to compete with existing suppliers once you've sunk all that capex.

Hence i don't think you will see any corperate interest.