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Isotope signatures of gem minerals

Giuliani, G. ; Fallick, A.E., Wooshin Gemological Institute of Korea

Isotope signatures of gem minerals

Giuliani, G. ; Fallick, A.E.

Wooshin Gemological Institute of Korea, 2018, 5, 2-9

Introduction :

Natural variations in isotopic ratios for gem minerals have been reported for only five light elements namely carbon and nitrogen for diamond, oxygen for oxides, and hydrogen, oxygen and boron for silicates, and heavier elements such as copper for turquoise and sulphur for lapis-lazuli. Stable isotope geochemistry deals with isotopic variations that arise from isotope exchange reactions or mass-dependent fractionations which take place during the physical and chemical processes responsible for the formation of gems. The magnitude and temperature dependence of isotopic fractionation factors between minerals and their parental fluids permit to reconstitute the geological history of gems in terms of source of the element and origin of the fluids. Here, we will focus on some gem minerals viz diamond, ruby, sapphire, spinel, emerald, zoisite, grossular garnet and agate. We shall demonstrate by different examples that the isotopic signatures used for their identification are directly controlled by their geological history.

publié jeudi 5 juillet 2018