Significant enrichment of Ga, Rb, Cs, REEs and Y in the Jurassic No. 6 coal in the Iqe Coalfield, northern Qaidam Basin, China—A hidden gem

Abstract This paper presents new data concerning the mineralogy and trace element geochemistry of the enriched rare metals in the Jurassic No. 6 coal from the Iqe Coalfield, Qaidam Basin, China. The conclusions of this study are based on new data and evidence that suggest the considerable enrichment of Ga-Rb-Cs-REEs and Y in the No. 6 coal of the Iqe Coalfield may be a hidden treasure with yet-to-be-realized additional economic potential, if such rare metal enrichment is proven across the whole area of Iqe Coalfield. The No. 6 Coal is enriched in Al 2 O 3 , SiO 2 , Na 2 O, MgO, P 2 O 5 , K 2 O, TiO 2 , Rb, Cs, Ga, Sc, V, Cr, Cu, Ba, W, Pb, Th, and REY, especially in Ga, Rb, Cs and H-REY, compared to world coals. The average contents of Ga, Cs, Rb, and REY are 3.1, 12.3, 6.0 and 3.5 times higher than those of world bituminous coals, respectively. Ga may occur in clay minerals (e.g., kaolinite), particularly in K-rich clay minerals (e.g., illite), which are thought to be derived from the Qilian Mountain Range. These minerals are probably the hosting phases for both Rb and Cs in the coal studied. REEs and Y in the coal are more likely to be associated with phosphates. The combustion products (e.g., fly and bottom ash) derived from those coals may be further enriched in these valuable rare metals and have economic potential in terms of the recovery of Ga, Rb, Cs, REEs and Y, providing additional economic value to this coal deposit.