Might aswell take the shovel and dig some up as some results are...

Might aswell take the shovel and dig some up as some results are from surface. Bhp deposit is 1km underground.   

I don't think capex is the problem as the fertiliser industry is worth $175 billion and this deposit is close to ports etc. you should probably Google feldspar and Brazil fertiliser technology and read a few articles.

Here is one article.

http://news.mit.edu/2014/new-source-potassium-fertilizer