NI 43-101 Preliminary Economic Assessment - Verde Potash

Verde Potash Plc 12-5
Cerrado Verde Project
NI 43-101 Preliminary Economic Assessment
Properties of kriging (Cressie 1993, Chiles & Delfiner 1999, Wackernagel 1995)
The kriging estimation is unbiased:
The kriging estimation honors the actually observed value:
The kriging estimation assumptions hold. However (e.g. Cressie 1993):
As with any method: If the assumptions do not hold, kriging might be bad.
There might be better nonlinear and/or biased methods.
No properties are guaranteed, when the wrong variogram is used. However typically still
a 'good' interpolation is achieved.
Best is not necessarily good: e.g. In case of no spatial dependence the kriging
interpolation is only as good as the arithmetic mean.
Kriging provides correctness of the variogram.
Additional to the drilling samples, channel composites samples, from complementary sampling
campaign were used, after a test of adequacy of support. Figure 12-9 shows the estimation steps
undertaken in the Cerrado Verde estimation.
12.1.6 Resource Reporting
The grade estimates for all domains have been classified as Inferred based on the confidence
levels of the key criteria that were considered during the resource estimation. Key criteria are
tabulated below. A summary of confidence levels of the several items involved for the resources
estimation for the Cerrado Verde deposit is provided in Table 12.1.6.1 below, reflecting the
updated resources for Targets 4, 6, 7, 10 and 11.
SRK Consulting (U.S.), Inc. September 16, 2011
Cerrado Verde_NI 43-101 PEA_343500.020_007_KG