http://www.forbes.com/sites/richardfinger/2012/11/06/how-arizona-is-heping-america-reduce-dependence-on-foreign-natural-resources/

Passport Potash (PPRTF.pk) currently a tiny $36mm market cap pink sheet listed Vancouver, Canada based firm controls 122,000 acres of land through state leases or direct ownership. Its recently updated National Instrument 43-101 (mineral resource estimate) more than doubled Indicated Resources and increased Inferred Resources nearly 15%. Indicated Resources might be analogous to “proved” reserves in oil jargon; you know where the fish are in the lake, you just have to go catch them. The NI 43-101report is the required first step in the multiyear approval process and is carried out only by registered geologists or geophysicists, in this case German firm ERCOSPLAN. At current potash prices of around $450 per ton Passport Potash may be sitting on reserves with a gross value of $50 billion…..and this report has surveyed only 37% of Passport’s land holdings.