Gemmological and Vibrational Spectrum Characteristics of Micaceous Quartzose Jade "Strawberry Crystal"

Abstract

Micaceous quartzose jade is a new kind of jade recently appeared on the market, and its trade name is "strawberry crystal". In view of the problems faced in the tests and researches of the jade, microscopic laser Raman spectrometer, Fourier transform microscopic infrared spectrometer and X-ray energy spectrometer were used to study the characteristics of mineralogy, vibration spectrum and colouring mechanism of the jade. The results showed that the micaceous quartzose jade is mainly composed of crystalline quartz and the secondary (colouring) mineral is manganese-iron bearing muscovite with typical scaly and granular structure. The formation of the purplish red hue of this kind of mica is closely related to the 554 nm absorption peak caused by 6A1→4T1 (4G) transition. The 445 nm absorption peak is caused by the 6A1→4T2 (4G) transition of delectron of the outer layer of the Mn2+, and the 516 nm absorption peak is caused by the spin forbidden transition of Fe2+. The infrared absorption band of manganese-iron bearing muscovite caused by stretching vibration of Al-(Fe, Mn)-OH is located at 3 616 cm-1, and a group of Raman peaks caused by silica backbone vibration are located at 1 071, 746, 697, 628 cm-1 and 408 cm-1, respectively. The Raman peaks caused by lattice vibration and cation exchange are located at 261 cm-1 and 191 cm-1 respectively, which are distinguished from similar mica group minerals.