Geochemical and mineralogical characterization of emeralds from La Arcadia mine, Colombia

Analyses were carried out on 514 emeralds, 439 from Colombia (15 from La Arcadia, 276 from other mines of Muzo district, 102 from other districts of the western belt and 46 from the eastern belt) and 75 from other countries, to find systematic trends or chemical composition characteristics that discriminate the Arcadia emeralds for provenance purposes. Principal Components Analysis (PCA) was carried out to compare La Arcadia mine against emeralds from other deposits around the world, mines from the eastern belt, mines from other districts, and mines of the same district. Additionally, petrographic analysis was performed on 20 polished thin-sections of representative veins and breccias from the La Arcadia mineralization. The chemical composition of Colombian emeralds is characterized by a high concentration of Vanadium (>2000 ppm), however, La Arcadia emeralds have a lower concentration than other deposits from Colombia, also the elements that substitute for Al have low concentrations. Emeralds observed in La Arcadia are associated with a hydrothermal alteration that affected a conspicuous black level of siltstones and the typical paragenesis consist of dolomite, albite, mica and emerald in veins and breccias.