Classic Gemological Characteristics Of Ruby And Sapphire From Muling,Heilongjiang Province,China

In this study,the gemological quality and characteristics,and provenance-related features of fancy-color sapphire and ruby from Muling are first reported with comprehensive analytical results.Muling corundum samples exhibit a wide spectrum of hue and saturation.Mineral inclusions(e.g.,rutile,zircon,anorthite,and pyrope)as well as other distinctive internal features(e.g.,polysynthetic twinning accompanied by intersecting tubes,iridescent hexagonal thin films,and angular color zoning)are identified by microscopic observation and Raman spectroscopy.The true relationship between color and trace element chemistry of sapphire in various colors are revealed by quantitative UV-Vis-NIR spectroscopy and in-situ LA-ICP-MS.Zircon inclusions in Muling deep blue sapphires were studied in-situ with modern measurement techniques.Their geologic ages,and their formation information were obtained to assist the investigation of Muling sapphires.Micro-structures of zircon inclusions were directly revealed by cathodoluminescence images,exhibiting two diagnostic patterns from cores to rims.The in-situ U-Pb ages are obtained from these distinct regions which were indicated by luminescence.Host sapphire-related rims derived ages of 9 to 8 Ma,while cores yielded much older ages of more than 110 Ma.The true ages of Muling deep blue sapphires were constrained to 9-8 million years old.A close relationship could thus be verified between these sapphires and the Late Miocene basaltic eruptions of Dunhua-Mishan graben.To assess the characteristics of Muling sapphire against well-known corundum sources worldwide,inclusion analysis and trace element discriminant diagrams are utilized.Analytical results indicate that Muling sapphire originated from a more diverse geological environment than typical magmatic or metamorphic origin.The macroscopic to microscopic studies of rubies and sapphires in Muling demonstrate that typical magmatic deposits can produce unique and atypical varieties of high-quality rubies and sapphires.Muling rubies and sapphires have changed the perception of premium colored gemstone resources in China.The excellent gemological nature also proves the great potential of this resource.