Cut-off grades and optimizing the strategic mine plan

The AusIMM releases the latest addition in its spectrum series on 17 November. Written by AMC Principal Mining Engineer, Brian Hall, it is available from The AusIMM online shop.

The foreword is reproduced here with the kind permission of The AusIMM.

At a time when the mining industry is reviewing its performance and approach in delivering value to shareholders, this book provides the intellectual tools needed by mine managers in order to turn what their directors are promising into reality. Too often, good intentions at a board level do not translate into appropriate actions by technical staff in mine planning and mine optimisation. Inappropriately calculated cut-offs cause many operations to mine and process large quantities of material that does not add value to the operation or its owners.

This book is a worthy successor to Ken Lane’s 1988 book The Economic Definition of Ore, which is now out of print. Mr Hall has built upon the theory in a very readable manner that will be readily understood by mining engineers and geologists, but this book goes well beyond Lane’s mathematics and explains how mine planning and optimisation are undertaken using the latest tools and techniques. All explanations are in plain language and are obviously the result of many years of practice in this field, and of training others in the techniques.

The gold industry, in particular, will welcome this book as it seeks to move from a focus on ounces in reserves or ounces of annual production to a focus on cash flow and the payment of regular dividends. With the emergence of gold contracts for difference (CFDs) in recent years, gold stocks no longer provide leverage to the gold price. It is essential that operators understand that many of the ounces they have previously claimed in resources and reserves are break-even ounces or even loss-making ounces and should be left in the ground, at least until later generations with new technologies can turn them to a profit.

While the primary appeal of this book will be to mining engineers and geologists, metallurgists and other specialists must contribute to the mine optimisation process and will benefit from the concepts explained. Corporate managers, company directors, mineral economists and in particular mining analysts should take the time to work through the concepts, if only to understand just how complex mining and mine optimisation really are.

A book that has the potential to transform the performance of an industry comes along only once in a generation or so. This is one of those books. Readers who take the trouble to understand the concepts and processes and put them into practice will gain a valuable advantage over their competitors, both for their employers and for their own careers.