This book provides a comprehensive review of gem corundum origins worldwide, highlighting the enduring value of rubies and sapphires despite synthetic alternatives. By delving into natural corundum origins and associated minerals, this knowledge boosts corundum prices and intensifies market trade. The book explores formation conditions and key evidence such as trace elements, mineral inclusions, and stable isotopes. These findings elucidate corundum’s origin, linking to the rock types and geological occurrences. Drawing from high-impact journals, books, and the author’s research, it offers valuable insights into synthetic processes and treatments. Catering to mineralogists, geologists, gemmologists, students, and gem traders, the book serves as a valuable reference for identifying gemstone origins. Its rarity in the market makes it particularly valuable for enthusiasts and professionals. As researches in this field continue to grow, this book bridges the gap by making complex terminology accessible to a wide audience.

Gems have been used in the manufacture of jewellery and as ornaments since antiquity. Considering gems, recent statistics have shown that about 15 billion Euros are annually at stake. Nowadays, gemmology, i.e., the study of gem materials, is one of the most expanding fields in the earth sciences, positioned between academia and industry. As an applied science, in gemmology, the instruments used should be non- or microdestructive, and their cost should be reasonable both in terms of equipment and time consumption. Gemmology can also be used contribute to the development of pure science and in some cases, destructive techniques may have to be used. Taking into account the fact that gems are albeit rarely available for scientific research, this compilation of 20 articles by around 100 researchers from over 30 different institutions situated in 20 countries from around the globe, presented in the Special Issue entitled “Mineralogy and Geochemistry of Gems”, offers very good examples on the application of various methods for their study which will hopefully contribute to our better understanding of gem formation in general and will enhance scientific debates attracting more scientists from various disciplines to get involved in this field.