Mineralogical and Spectral Characteristics of Turquoise and Associated Minerals from Baghu, Iran

The Baghu turquoise deposit is located in the Kuh-Zar region, Iran. The turquoise from Baghu deposit is of high quality, which has not been used for commercial exploitation yet.4 pieces of light blue to blue turquoise samples were selected from Baghu deposit to investigate the mineralogy and spectroscopy of the turquoise there by scanning electron micrometer(SEM), Fourier transform infrared spectrometer(FTIR), Raman spectrometer and UV-Vis spectrometer. The SEM images showed that the turquoise microcrystals occurre as long columnar, plate and scale aggregates with the size ranging from 1 to 5 μm. According to the test results of energy dispersive spectroscopy and Raman spectroscopy, the associated minerals are tourmaline, mica, gypsum, pseudomalachite, chrysocolla, barite, pyrite, quartz, jarosite, alingite and rutile. The tourmaline has an radial pattern and quartz is in good idiomorphology. According to the associated mineral association, it is inferred that the turquoise ore-forming mother rock is magmatic rock, and the associated minerals are tourmaline, malachite, chrysocolla and pseudomalachite, which can be used as one of the characteristics to distinguish the origin. Both Raman spectra and infrared spectra of turquoise showed the absorption peaks of H₂O, OH^- and PO₄^3- groups, which are consistent with the characteristics of turquoise from the other regions. The bands at 422, 429 nm and 650~670 nm in UV-Vis spectra of turquoise are respectively attributed to Fe and Cu ions.