gems, beryl, emerald, Pakistan, Swat

Swat Valley has become an important source of emeralds, including recently discovered trapiche-type crystals. In this study, emerald samples from Swat were examined by standard gemological testing, UV-Vis-NIR, FTIR, Raman analysis, EDXRF, and LA-ICP-MS. The study found three-phase hexagonal inclusions consisting of water, gaseous carbon dioxide and nitrogen, and a magnesite crystal. The gaseous mixture in two-phase inclusions is characteristic in both trapiche-type (CO₂ + N₂) and non-trapiche samples (CO₂ + N₂ + CH₄). Mineral inclusions of hematite, magnetite, rutile, graphite, and siderite are reported for the first time. Regular non-trapiche-type Swat emeralds contain high chromium (avg. 7471 ppmw), alkali metal (avg. 21,040 ppmw), magnesium (avg. 34,263 ppmw), and iron (avg. 9265 ppmw), as well as scandium (avg. 633 ppmw). Infrared spectra show that the absorption of type II H₂O is stronger than that of type I H₂O. Logarithm plots of trace elements appear to be diagnostic. Based on Raman spectroscopy, the trapiche-type emeralds’ colorless core, light green hexagonal growth zone area, and green rim are emerald, while the six black arms are a mixture of hematite and graphite.