A study on visible shortwave infrared and thermal infrared spectral characteristics of beryl: Implications to the beryllium resource exploration using remote sensing technology

Beryllium is a key strategic metal, which is of great significance to the development of science, technology and industry in China. There will be a large shortage of demanded beryllium supply by 2030. Previous researches have shown that there is relatively high exploration potential of beryllium resource in the Himalayan area. However, the high altitude of the Himalayan area has severely restricted the effectiveness of traditional geological prospecting methods. Hyperspectral remote sensing technology is characterized by the wide detection area and non-invasive measurement. If it can directly identify beryllium-containing minerals, it will provide important technical support for the exploration of beryllium resources in high altitude areas. Beryl is the most typical ore mineral in beryllium deposits in China. In this paper, the spectra of beryllium-bearing beryls were measured by using the visible-shortwave infrared spectroscopy and thermal infrared spectroscopy. Meanwhile, based on the simulation of main mineral characteristics of pegmatitic beryls, some mixed mineral samples with different percentages of beryls have been prepared for undertaking their short-wave infrared spectral quantitative study. The experimental results show that beryl has absorption characteristics at 850 nm, 1150 nm, 1400 nm, 1900 nm, 2055 nm, 2155 nm and 2200 nm in visible-shortwave infrared spectra, and reflection characteristics at 960 cm–1 (～10417 nm) in thermal infrared spectra. At the same time, the absorption peak depths and first derivatives at 850 nm and 1400 nm are increased with the increase of beryl contents in the mixed samples. By comparing with previous remote sensing spectral features of ground objects, it is found that the direct identification of beryl in pegmatitic beryllium ore by using the thermal infrared hyperspectral remote sensing is highly feasible. The visible-shortwave infrared remote sensing technique using the sun light as light source will be affected by the atmosphere, and its feasibility for directly identifying beryl is relatively low. However, by using artificial light as light source, feasibility for directly identifying beryl in a short distance is relatively high. Additionally, the content of beryl in pegmatite ores can be retrieved according to the absorption peak depth and other indicators.