The 1.0 m composite p-XRF samples were used to prepare interpretations for vanadium and uranium mineralisation at 560ppm V (1,000 ppm V2O5) and 100 ppm U (118 ppm U3O8) respectively. Both vanadium and uranium mineralisation occurs as multiple, variably mineralised lodes (fourteen vanadium and twelve uranium lodes), within the respective black shales. Vanadium and uranium mineralisation is broadly co-located, often overlaps but are not coincident and there is no correlation between the two variables.
The coefficient of variation and coefficient of skew for both vanadium and uranium were sufficiently low that top-cutting was not necessary for either variable and ordinary kriging was selected as the estimation technique. Normal-score transformed variograms were used to model the vanadium and uranium grade continuity and the back-transformed continuity models used for estimation. Only the footwall and hanging wall mineralisation of the South shale horizon had sufficient sampling to derive variography. The domains that had insufficient samples to support variography used variogram that best matched the stratigraphic position and/or statistical parameters.
All shale, fault and mineralisation boundaries were treated as hard boundaries for the purposes of estimation. The estimate used a parent block size of 25 mE x 10 mN x 5 mRL which was rotated parallel to the stratigraphy and the parent blocks were discretised at 8 E x 4 N x 2 RL. The block size was derived by kriging neighborhood analysis.
The search ellipse was orientated parallel to the black shales and in the plane of the mineralisation. The drillhole spacing is variable, ranging from 40 to 500 m spaced sections, and from 40 to 220 m along a section at Chubu. The drilling at Yokwang and Seongdong prospects occur predominantly as single hole sections. A four pass search strategy was employed to overcome the inconsistent hole spacing. The primary search used a radius of 250 m along strike and down dip, and a search of 40 m across strike, with a restriction on the number of samples per drillhole, such that a minimum of two drillholes were required to inform the estimate. Subsequent passes had no restriction on the number of samples per drillhole. The second search used the primary search ranges, the third search doubled the primary search and the fourth search tripled the primary search.
The better informed zones were estimated using a minimum of 8 and a maximum of 30 samples for vanadium and 8 and a maximum of 36 samples for uranium for the first three estimation passes, and 4 to 15 and 4 to 18 samples for vanadium and uranium respectively for the fourth estimation pass. Lesser informed domains used 4 to 15 and 4 to 18 samples for vanadium and uranium for all estimation passes. The maximum distance of extrapolation was 375 m in the plane of the mineralisation.
Validation consisted of initial visual validation, followed by a comparison of the composite and model averages and finally, swath plots by easting, northing and elevation, all of which exhibited good correlation between the composite and estimated values and maintained the composite sample grade trends. Currently, there are 41 specific gravity determinations available, with values that ranged from 2.48 to 3.05 and averaged 2.72. A default density of 2.6 t/m3 was assigned to the 2013 Mineral Resource on the basis that typically specific gravity values are slightly higher than the true dry bulk density and as shale dry bulk density values range from 2.4 to 2.7 t/m3 . The resource classification has incorporated all aspects of data quality, spatial distribution, geological and grade continuity, as well as estimation metrics (kriging variance, kriging efficiency and slope of regression). Only material shallower than 300 m vertically below surface has been classified as a Mineral Resource, as material deeper than 300 m vertically is considered unlikely to support open pit mining. Mineralisation within a 200 m exclusion buffer around the road tunnel infrastructure that cross-cuts the mineralization has been excluded from the Mineral Resource. Most of the material shallower than 300 m vertical depth has been classified as an Inferred Mineral Resource. There is a small area adjacent to the 2013 drilling where the vanadium mineralization has been classified as an Indicated Mineral Resources as a function of the demonstrated geological and grade continuity, good geological confidence and there being sufficient supporting information to inform modifying factors for that area. The uranium only resource has been classified as an Inferred Mineral Resource at best, because of the lower precision observed to date in the p-XRF data.