GEMMOLOGICAL PROPERTIES OF A NEW TYPE OF GUILIN HYDROTHERMAL SYNTHETIC EMERALD

The new type of Guilin hydrothermal synthetic emerald is thick plate or short prismatic crystal with bluish green or green colour. Its crystal configuration consists of two hexagonal prism a (1120) and m (1010) and the basal pinacoid c (0001). EPM analyses show that SiO₂ and Al₂O₃ are more than those of natural emeralds and Cr₂O₃ is similar to that of natural and other synthetic counterparts. Visible absorption spectra show Cr 3+ absorption peak. IR spectra show typical water absorption and characteristic absorption peaks of 5109, 5274 and 5448cm ^-1 in the range of 5000~5500cm ^-1 as well as only one peak of 3701cm ^-1 in the range of 3400~4000cm ^-1. Typical dreg inclusions, bertrandite crystalized inclusions, two-phase inclusions and regular growth line are discovered in the crystal. Other properties of the new type of Guilin hydrothermal synthetic emerald are similar to those of Linde, Biron and Tairus hydrothermal emeralds.