Distinction of Gem Spinels from the Himalayan Mountain Belt

Abstract

Gem spinel deposits in Myanmar, Vietnam and Tajikistan have their formation in association with Himalayan orogenesis. Gem-quality orange, pink, red and purple spinels from deposits at Mogok (Myanmar), Luc Yen (Vietnam), and Kuh-i-Lal (Tajikistan) have been investigated by 'standard' gemological testing and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Microscopic examination yielded apatite and calcite inclusions together with octahedral negative crystals to be most frequently present in Mogok spinels. The presence of dislocation systems and titanite inclusions are indicative inclusion features for spinels from Luc Yen. Trace elements such as Ti, Fe, Ni, Zn, Zr and Sn differ slightly in spinels from the sources investigated. A distinction of spinels from these deposits is therefore possible by trace element chemistry. This is especially helpful for gem spinels, which often show few inclusions or completely lack inclusion features.