1. Occurrence of rare earth elements and classification of minerals Occurrence of the rare earth element in the earth's crust are the following three: (1) participate in the mineral crystal, constituting the essential mineral components, forming an independent minerals (e.g., monazite, bastnaesite), which is a rare earth element in the crust The main form of occurrence in (2) is dispersed in rock-forming minerals and other rare minerals in the form of isomorphic substitutions (calcium, strontium , barium, manganese, etc.), which is a secondary form of occurrence; 3) Adsorption in the form of ions on other mineral surfaces or between particles, which is a rare form of occurrence. According to the chemical composition of rare earth minerals, the rare earth minerals that have been discovered can be classified into nine categories, and various typical rare earth minerals are listed in Table 1. Table 1 Classification of rare earth minerals category Main mineral Fluoride Yttrium fluorite, calcium fluoride, sodium stone yttrium, cerium ore fluoro Carbonate, fluorocarbonate Bastnasite, yellow river mine, barium carbonate mine, etc. Phosphate Monazite, xenotime Silicate Gadolinite, scandium, yttrium stone Oxide Fergusonite ore, aeschynite, dilute black gold ore Arsenate Arsenic ore Borate Mink calcium borax Sulfate Fluorine hydrate Citrate Antimony ore Second, the main industrial minerals and their physical and chemical properties At present, there are about 250 kinds of rare earth-containing minerals found in the world, and there are about 50 to 60 kinds of rare earth minerals with research and utilization value. There are only 10 kinds of rare earth minerals with industrial exploitation and practical value. The physical and chemical properties of rare earth minerals are listed in Table 2. Table 2 Physical and chemical properties of rare earth minerals Mineral name Chemical properties Molecular formula REO% Soluble Bastnasite CeCO 3 F 74.77 Soluble in HCl Monazite CePO 4 67.76 H 2 SO 4 , HCl, H 3 PO 4 are slightly soluble in NaOH Phosphonium ore YPO 4 63.23 Soluble in H 2 SO 4 , H 3 PO 4 slightly soluble in NaOH Fluorocarbon calcium strontium ore Ce 2 Ca(CO 3 ) 3 F 2 60.30 Soluble in HCl, H 2 SO 4 , HNO 3 Silicon germanium ore Y 2 FeBe(SiO 4 ) 2 O 2 51.51 Soluble in HCl, slightly soluble in NaOH Easy stone (CeThY)(TiNb) 2 O 6 29.36 Soluble in H 2 SO 4 , H 3 PO 4 soluble in HF, H 2 SO 4 +(NH 4 ) 2 SO 4 Niobium perovskite Ce (NaCeCa)(TiNb)O 3 28.71 Insoluble in HCl, H 2 SO 4 , HNO 3 soluble in HF Complex gold mine Y(TiNB) 2 (O·OH) 4 29.28~33.43 Soluble in H 2 SO 4 , H 3 PO 4 , HF Black gold mine Y(TiNbTi) 2 (O·OH) 6 20.82~29.93 Soluble in HF, H 2 SO 4 , H 3 PO 4 Brown sugar mine YNbO 4 39.94 Soluble in H 2 SO 4 , HNO 3 (Continued Table 2) Mineral name Physical properties Density g∕cm 2 hardness Specific magnetic susceptibility × 10 -6 cm 3 ∕g Dielectric constant Crystal form 2 fluorocarbon antimony ore 4.72~5.12 4 to 5.2 12.59~10.19 5.65~6.96 Trigonal system Monazite 4.83~5.42 5 to 5.5 12.75~10.58 4.45~6.69 Monoclinic system Phosphonium ore 4.4~4.8 4~5 31.28~26.07 8.1 Orthogonal system Fluorocarbon calcium strontium ore 4.2 to 4.5 4.2 to 4.6 14.37~11.56 Trigonal system Silicon germanium ore 4.0 to 4.65 6.5~7 62.5～49.38 Monoclinic system Easy stone 5~6.4 4.5 to 6.5 18.04~12.92 4.4~4.8 Orthorhombic system Barium perovskite 4.58~4.89 5.8~6.3 6.54~5.23 5.56~7.8 Isometric crystal system Complex gold mine 4.28~5.05 4.5 to 5.5 21.05～18.00 Orthorhombic system Black gold mine 4.2~5.87 5.5 to 6.5 27.38~18.41 3.7~5.29 Orthorhombic system Brown sugar mine 4.89~5.82 5.5 to 6.5 29.2~21.16 4.5～16 Tetragonal system
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