Cut-Off Grade 2 (Equivalent Grade)
This article deals with Equivalent Grade and why it is so important in the mineral resource industry. The factors that are applied in the conversion of In-Situ grades (like those generated by geological block models) to Equivalent Grade are described and the calculation process that is used for the conversion is presented.
Cut-Off Grade 3 (Poly-Metallic Deposits)
In this Article I describe the complexities with calculating Equivalent Grade for poly-metallic deposits. A worked example is presented for a Copper/Gold/Silver deposit. The process used to express the Equivalent Grade in terms of any of the three major metals of interest is explained.
Cut-Off Grade 4 (Tonnage, Grade, and Costs)
In this article the concept of Cut-Off Grade is tied together with the concept of the Tonnage/Grade relationship for the resources and reserves for any given deposit. The importance of selecting the right Cut-Off Grade and how it is applied to determine the specific tonnage and grade of a deposit is explained. A simple gold deposit is used as an example for both resource and reserves estimation at any given Cut-Off Grade. The importance of accurately converting the tonnage/grade relationship from a resource to a reserve is discussed. The ramifications of getting the Cut-Off Grade wrong in determining the tonnage and grade for a deposit and the economic impact of that error is presented. Finally, the appropriate selection of the cost base used to establish the Cut-Off Grade is discussed, specifically what should be included and what should be excluded from the cost base.
Cut-Off Grade 5 (Incremental Ore)
In this article the concept of Incremental Cut-Off Grade is explored. What is incremental cut-off and incremental ore? How, when, and where should incremental ore be added into a mine plan. What happens when you can no longer deliver a full production plan at grades above the all-in-sustaining cut-off grade? Strategies to rationally apply decision making tools based on economic contributions from low grade material are presented and explained.
Cut-Off Grade 6 (Sustaining Capital)
In this article, the importance of including Sustaining Capital in the total cost used to calculate Break Even Cut-Off Grade (BECOG) is explored. In most cases, including Sustaining Capital costs in your cut-off calculations will increase your cash flow and resulting NPV.