corundum, geology.11, gems

An edited compilation examining the geological origin, occurrence, exploration, and evaluation of gemstone deposits worldwide. The first two sections reproduce 21 contributions covering topics such as diamond formation in kimberlite, jadeite genesis through low-grade metamorphism, agate and thunder egg development, Brazilian topaz deposits, Sri Lankan sedimentary gem deposits, and the structure responsible for precious opal’s colour. Exploration studies consider magnetic characteristics associated with Australian opal deposits, sodium as a geochemical indicator of Colombian emerald mineralization, glacial tracing of Canadian kimberlite, and the economic evaluation of alluvial diamond deposits. Regional accounts describe nephrite, amethyst, agate, and other gem materials in North America. These papers are followed by VanLandingham’s extensive review of the literature and a substantial bibliography, supported by author, mineral and rock name, and subject indexes. The review encompasses gemological research, mineral composition and structure, inclusions, physical properties, and deposit geology. Particular attention is given to the conditions that produce gem-quality material and the difficulties of assessing deposits whose valuable crystals may occur irregularly within a larger mineralized body. Combining technical research with more accessible geological accounts, the volume serves as a reference for geologists, gemologists, prospectors, and collectors investigating gemstone formation and distribution.