The gold-processing industry is experiencing change. As free-milling and oxide ores become depleted, more complex polymetallic and refractory ores are being processed, coupled with increasing pressure for stricter environmental compliance. Recent years have also seen a steady reduction in mineral processing and metallurgy graduates and a gradual loss of older operating experience. A contribution to documenting current and future best practice <...>

High-pressure mineral physics is a field that is strongly driven by the development of new technology. Fifty years ago, when experimentally achievable pressures were limited to just 25 GPa, little was known about the mineralogy of the Earth’s lower mantle. Silicate perovskite, the likely dominant mineral of the deep Earth, was identified only when the high-pressure techniques broke the pressure barrier of 25 GPa in the 1970s. However, as the maximum achievable pressure reached beyond 1 Megabar (100 GPa) and even to the pressure of Earth’s core on minute samples, new discoveries were increasingly fostered by the development of new analytical techniques and improvements in sensitivity and precision of existing techniques.

In this book we decided to attach the permil sign (‰) to all Li isotopic quantities. One way of viewing stable isotopes denoted by δ is that the arithmetic sets the results as being part-per-thousand quantities, so to place the ‰ on a value is redundant. However, this implies a certain familiarity from the reader. Our decision regarding the ‰ in this volume was guided by the potential that the audience may include those not so steeped in the thinking of stable isotopes. This calls to mind a historical note regarding Li isotopes. Readers of the early literature on the subject (beginning with Chan in 1987) will find papers that use δ6Li. Prior to 2000, using the now-accepted δ7Li notation was viewed as an unwanted usurpation by at least one prominent geochemist. Nevertheless, being clear is important, and although δ7Li was not the first notation employed, it follows stable isotope convention. We find that students have a hard enough time understanding isotope geochemistry, so to oppose the notation used in virtually all systems (positive values are isotopically heavier than negative values) invites confusion. Hence, our use of the ‰ is a further step to make this compilation clear for all.

The Global Optimiser used by Whittle Consulting has gone through three major versions to date. The first was based on the Milawa optimisation algorithm; it worked, but had many shortcomings. The second, known internally as ProberA, had a different approach to optimisation in that it used a series of random starting points and found the nearest local NPV maximum to each.