A gemstone refers to a cut and polished piece of mineral crystal that can be utilized to create jewelry or other adornments. Gemstones are created underneath the surface of the Earth and may contain traces of other minerals known as inclusions. The majority of gemstones are found in alluvial gravels and igneous rocks but metamorphic and sedimentary rocks can also contain gem materials. Gemstones are classified into different species and groups on the basis of chemical composition and crystal structure. The most significant gemstone species include corundum, quartz, beryl, tourmaline and garnet. The majority of gemstones are hard but some soft minerals are also utilized in jewelry due to their luster or other physical qualities which hold aesthetic value. This book unravels the recent studies on the geology and mineralogy of gemstones. With its detailed analyses and data, it will prove immensely beneficial to professionals and students involved in the study of gemstones at various levels.