This chapter covers both primary and secondary diamond deposits because both have played an important role in the science of diamond geology, and in the gem diamond trade. A significant scientific research focus since the 1980’s has been on lithospheric diamonds, sourced from kimberlite mines; however, some of the first and most important discoveries of sublithospheric diamonds were made from the alluvial diamond fields of Australia (Ororoo), Brazil (Juina) and West Africa (Kan Kan) as described in Stachel et al. (2022, this volume). Africa, where the beneficiation of both primary and secondary diamond deposits has been substantial, provides a ready comparison of the importance of both of these types of deposit. Since the discovery of diamonds in Africa in 1854 until the end of 2019, Africa has produced almost 3.6 billion carats (Bct) of diamonds out of a total global production of some 5.9 Bct (updated from de Wit et al. 2016). Of the 3.6 Bct African production it is estimated that 1.3 Bct have been mined out of placer and paleo-placer (including marine) deposits, which represents 22% of total global production. With the combined production of placers and paleo- placers from South America, India, Australia and Siberia it is estimated that close to 1.5 Bct (or just over 25% of the global production), have come from these deposits. Furthermore, these diamonds are typically better quality having survived erosion from a primary source, subsequent transport and deposition and hence are of higher carat value.
Authors: Bruce A. Kjarsgaard, Mike de Wit, Larry M. Heaman, D. Graham Pearson, Johann Stiefenhofer, Nicole Janusczcak, Steven B. Shirey
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