A Comparative Study of the Gemological Characteristics and Inclusions in Spinels from Myanmar and Tajikistan

Abstract

Currently, most of the popular spinels in the jewellery market come from Myanmar and Tajikistan. It is well known that provenance is one of the main factors affecting the value of a gemstone, and the geographic origin of a gemstone can be determined by examining its gemological and inclusion characteristics. This study systematically characterized the conventional gemology of spinels from Myanmar and Tajikistan and compared the inclusions in the spinels from these two countries by means of gemological microscopy and Raman spectroscopy. The results showed that most red and pink Myanmarese spinels were octahedral or contact twins, while Tajikistani spinels are slabbed or octahedral distorted crystals. Columnar zircon is frequently found in Tajikistani spinels but rare in Myanmarese spinels, appearing as tiny accessory inclusions. There are three types of carbonate inclusions (magnesite, dolomite, and calcite) in Myanmarese spinels, but Tajikistani spinels have only one (magnesite). In addition, spinels of different origins include special inclusions. Myanmarese spinels contain pyrite inclusions; Tajikistani spinels contain rutile and talc inclusions.