The tuff, a part of coal-bearing strata, in the Zhongliangshan coal mine, Chongqing, southwestern China, hosts a rare metal deposit enriched in rare earth elements (REE), Ga and Nb. However, the extraction techniques directly related to the recovery of rare metals in coal-bearing strata have been little-studied in the literature. The purpose of this paper is to investigate the extractability of REE, Ga and Nb in the tuff in the Zhongliangshan mine using the alkaline sintering-water immersion-acid leaching (ASWIAL) method. The results show that ASWIAL can separate and extract REE, Ga and Nb effectively under the optimized conditions of calcining at 860 °C for 0.5 h with a sample to sintering agent ratio of 1:1.5, immersing at 90 °C for 2 h with 150 mL hot water dosage, and leaching using 4 mol/L HCl at 40 °C for 2 h with a liquid-solid ratio of 20:1 (mL:g). The final leaching efficiencies of REE and Ga are up to 85.81% and 93.37%, respectively, whereas the leaching efficiency of Nb is less than 1%, suggesting the high concentration of Nb in the leaching residue, which needs further extraction.

This paper presents the mineralogical and geochemical compositions of coal benches and non-coal (carbonaceous rock benches, parting, roof and floor) samples from the No. 1 Coal in the Longtan Formation of the Permian-Lopingian epoch from the Shugentian Coalfield, eastern Yunnan Province, southwestern China. The coal is rich in Nb, Ta, Zr, and Hf, which were derived from the Kangdian Upland with the dominant compositions of the Emeishan basalt. The minerals identified in the samples include mixed-layer illite-smectite, kaolinite, quartz, siderite, and minor calcite, pyrite, anatase and ankerite. Albite and chamosite occur in the roof and floor samples. The parting sample (SGT1-2p) is characterized by abundant siderite (64.9%) and calcite (20.1%), and one carbonaceous rock sample SGT1-11 contained a large amount of pyrite (26.1%). Four factors were responsible for the geochemical and mineralogical compositions in the samples; namely, the terrigenous detrital materials transported from the Kangdian Upland, direct volcanic ash inputs, multi-stage inputs of hydrothermal fluids, and marine influences. The co-existence of siderite and pyrite was attributed to a continental-marine transitional environment.

Ultraviolet-visible (UV-Vis) absorption spectroscopy has been widely exploited by the gemstone industry, as it can be used to identify natural and synthetic gemstones, type of gemstone, and the origin of their color, all using a non-destructive method. Current spectrometers for gemstone identification capture required spectral information, however, they have a few noticeable disadvantages: it is difficult to customize the setup (adding fluorescence/LED illumination, implementing new software functions to capture time series data etc.), they can have long measurement times, and high maintenance cost. Due to these reasons, we have designed a UV-Vis absorption spectrometer that can capture spectra from 220 nm to 990 nm, with a measurement time up to 10 seconds. The device can be used to measure both loose/mounted gemstones, with almost no sample size limitation. They have been installed globally for diamonds, colored stones and pearl production. Several new options are currently being developed for the current unit: new software functions such as time series spectra measurements and hardware updates specifically for diamond treatments and coating detection. Besides the UV-Vis wavelength range, a new approach is to further extend the current wavelength range (up to 990 nm) to the Near-Infrared (NIR) – Mid-Infrared (MIR) range (up to 5μm). Spectrometers based on up-conversion phenomenon of non-linear crystal have been utilized for this research. The target for this development is towards quick and easy operated gemstone screening.