A Practical Example of Grade Engineering Evaluation

Table of contents:

• Block Model Preparation for Mine Planning
• Mine Planning Parameters
• Open Pit Optimization and Design
• Underground Optimization and Design
• Economics (Comparisons)
• Key Benefits and Advantages
• Grade Engineering Evaluation Conclusions
• Worked Example of Block Model Macro

 

 

The Neytiri example evaluated the following Grade Engineering options:

• bulk sorting based on three sorting Cu Cut-Off grade (0.2%, 0.4% and 0.6% Cu)
• Screening for differential blasting of two metal products (Cu and Au) with three different high-energy charging Cut-Offs (0.2%, 0.4% and 0.6% Cu or 0.2g/tGrams per tonne , 0.5g/tGrams per tonne and 1.0g/tGrams per tonne Au) and three screening apertures (200mm, 150mm and 100mm)
• Screening for natural deportment at three apertures (100mm, 50mm and 25mm)

 

Estimating heterogeneity for GEGrade Engineering Options

Uniform conditioning (UC) was used to estimate the potential, In-situContained in unbroken ground. heterogeneity within a block.  The heterogeneity within a blockA spatially constrained unit within the resource model. was used to estimate the potential upgrades that could be achieved for bulk sorting and differential blasting Grade Engineering techniques.  The UCUniform Conditioning estimation assigns:

• the probabilistic proportion of a blockA spatially constrained unit within the resource model. being above a series of cut-off grades,
• the proportion of contained metal in the proportion of the blockA spatially constrained unit within the resource model. above a series of cut-off grades, and
• the resultant grade of the metal in the proportion of the blockA spatially constrained unit within the resource model. above a series of cut-off grades. 

The proportion of the blockA spatially constrained unit within the resource model. and the proportion of contained metal in that proportion of the blockA spatially constrained unit within the resource model. are numeric values between 0 and 1.  A larger proportion of contained metal within a smaller proportion of a blockA spatially constrained unit within the resource model. implies heterogeneity that may be exploitable using differential blasting and/or bulk sorting. 

Two UCUniform Conditioning models for the Neytiri orebody were created for Cu and Au.  As the UCUniform Conditioning models were prepared separately, a means to assign the correlation between Cu and Au was required to estimate the proportion of Au (Cu) likely to be present in the proportion of the blockA spatially constrained unit within the resource model. above a Cu (Au) cut-offgrade. 

For Grade Engineering techniques used in the Neytiri example, the Cu and Au correlation are used to estimate:

• bulk sorting performance of Au for a blockA spatially constrained unit within the resource model. based on a Cu sorting cut-off grade.  The UCUniform Conditioning model provides the proportion of the blockA spatially constrained unit within the resource model. and contained Cu metal and grade above the sorting Cu cut-off grade and the associated Au metal and grade are estimated using the Cu and AU correlation.

 
Associated data files for the practical example can be download below.
Base Case Open Pit Mine Planning Data
Base Case Underground Mine Planning Data
GE Open Pit Mine Planning Data
GE Underground Mine Planning Data