The geology and genesis of gem corundum deposits

The aim of this review is to present the state of the art on the geology and genesis of gem corundum deposits, including the main characteristics and classifications, to an audience of non-specialists, academic students, professional geologists and gemologists. The careful detailed descriptions and studies on the geology, mineralogy and structures of the deposits carried out over the last century provides a foundation to unravel their genesis through new field and laboratory research including petrography, mineralogy, gemology, fluid inclusions, and stable and radiogenic isotopes. Descriptive geology coupled with recent advances in geology of gems permits decoding of how some of these historical and fabulous deposits formed as well as to estimate exploration potential in the future. New oxygen isotope data are presented here for the first time.