Efficient identification and distinction of musgravite and taaffeite with the utilization of ATR-FTIR spectroscopy and Raman spectroscopy

Abstract

Taaffeite (BeMg₃Al₈O₁₆) and musgravite (Be(Mg,Fe,Zn)₂Al₆O₁₂) are two of the rarest gem kinds worldwide, and their scarcity greatly enhances their extraordinary worth. Due to their nearly matched physical properties, discriminating between the two gems using basic gemological equipment will be exceedingly difficult, considering that they both belong to the same mineral family. Distinguishing between these two categories is crucial due to the substantial variation in their rarity levels, which greatly impacts on their market pricing. Nevertheless, there is a lack of published data in the scientific literature about the spectroscopic characterization of musgravite and taaffeite.

In this article, ATR-FTIR spectroscopy successfully distinguished Tanzanian musgravite from taaffeite for the first time. In addition, Raman spectroscopy and EPMA are employed for the identification of musgravite and taaffeite specimens. The EPMA results confirm that the Tanzanian gems under investigation have similar elemental compositions to those of the same kinds of stones discovered from other sources. The peaks observed in the ATR and Raman spectra serve as indicators for distinguishing between musgravite and taaffeite gemstones, with the goal of simplifying the identification process. The ATR and Raman spectra of musgravite and taaffeite are comprehensively analyzed and found to be achievable. The main Raman bands used to identify Tanzanian musgravite are situated at 412 and 713 cm⁻¹, whereas for taaffeite, the significant bands were detected at 416 and 761 cm⁻¹. The distinct ATR bands observed at 773 cm⁻¹, corresponding to the vibration of Al–O, can be efficiently utilized as indications to differentiate Tanzanian musgravite from taaffeite. The results prove that ATR-FTIR spectroscopy, like Raman spectroscopy, is a very effective non-invasive method for rapidly distinguishing these precious gemstones.