Gemmological and Spectral Characteristics of Ruby from Winza, Tanzania

Rubies produced in the Winza region of Tanzania are highly transparent, have high colour brightness, high colour saturation and are often produced in large grain sizes, but few systematic studies have been carried out on the rubies from Winza, Tanzania. Systematic study and analysis of 10 ruby samples from Winza, Tanzania were carried out using conventional gemmological instruments, laser ablation inductively coupled plasma mass spectrometry, ultraviolet-visible spectrophotometer, Fourier transform infrared spectroscopy, Raman spectrometry and 3D fluorescence spectrometer. The results show that the rubies from Winza, Tanzania, contain pargasite inclusions, gas-liquid inclusions, blue colour zones, and negative crystal inclusions. The blue colour zone is associated with higher Ti elemental content and is of provenance significance. Rubies from Winza are characterized by high Cr and high Fe, all of which exceed 500×10^-6 and that it also contains trace elements such as Ti, Mg, V, Ni, and Ga. The UV-Vis spectrum shows a clear Cr spectrum and also exhibits the influence of Fe and Ti. The 3 160 cm^-1 absorption peak that is visible in almost all samples, is often accompanied by 3 240 cm^-1and 2 420 cm^-1 absorption peaks, called the "3 160 group". Raman spectra show scattering peaks related to the stretching and bending vibrations of the [AlO₆] group, with absorption peak at 416 cm^-1 caused by symmetric bending vibrations (O-Al-O_bend) showing the strongest spectral features. 3D fluorescence spectra show 4 clear fluorescence peaks and the λ_ex=408 nm/λ_em=694 nm peak is the strongest one.