NioCorp’s Elk Creek Superalloy Materials Project is located near Elk Creek, Nebraska. The deposit was discovered in the 1970s and initially explored by Molycorp, with NioCorp acquiring a land package covering the resource in 2009/2010. We have been involved in the project from helping locate drill holes to target resource infill areas through to acting as lead consultants for the multi-consultancy team that developed the 2017 feasibility study (FS). As part of a coordinated program, we have provided the geologic, geotechnical, and groundwater information needed to support the project’s development. The deposit contains niobium (Nb), titanium dioxide (Ti), and scandium (Sc).
Resource Estimation
In February 2015, we developed an initial resource estimate as the foundation for a preliminary economic analysis. This resource estimate also used historic drilling and other data from 2011 and 2014. PEAs were completed in May and September of 2015. Another drilling program consisting of five more holes began in 2015 and provided additional geotechnical and hydrogeological information. During this program, we conducted further assay and resource evaluation confirmation work. The 2017 feasibility study (FS) was based on the updated resource estimate as well as data from the 2015 drill holes and the re-assay of historical pulps.
Grade Estimation
We constructed a 3D geologic model for the project using Seequent Leapfrog®. We confined the grade estimation to a hard boundary of three grade shell domains defined at 0.3%, 0.4%, and 0.5% Nb2O5, with the estimation using only the composited samples from the same domain. The grade estimation for Nb2O5(%), TiO2(%), Sc(ppm) used an ordinary kriging (OK) algorithm supported by 5 m sample composites for all the mineralized units, with inverse distance weighting (IDW) to a power of 2. We then determined search distances from directional variograms calculated using the capped and composited samples. According to Canadian Institute of Mining (CIM) guidelines, the mineral resources are classified under the categories of Indicated and Inferred.
Mine Planning
Finally, we generated mine plans to meet the desired product quantities while maximizing net present value (NPV). Using an elevated cutoff grade and varying the cutoff on an area-by-area basis allowed delivery of a constant grade feed to the process facility. We conducted several iterations to trade off the operating and capital costs of the overall project against the size of the deposit and to maximize the NPV.
