Ann: Quarterly Activities Report , page-5

Another reason why SOL might be interested in RUM is the similarity between operating coal mines and fertiliser deposits - both involve removal of overburden, mining and beneficiation of the orebody and bulk shipments.
Even the harvesting of brines from the potash deposit is similar once the evaporation stage is complete.
A logical and maybe counter-cyclic move for SOL (as coal prices slip, fertiliser prices may well rise).
RUM is a good place to be.