锡石中铌钽赋存形式的研究

A STUDY ON THE MODE OF OCCURENCE OF NIOBIUM AND TANTALUM BEARED IN CASSITERITE

In the present paper the mode of occurence of niobium and tantalum in cassiterite has been studied, suggesting that the two elements are present in the form of individual minerals, namely tapiolite (a new mineral), and brown-red coarse and orange-yellow fine grained alvaralites. The ground sample grains sieved to about 200 mesh are treated with hydrofluoric acid and hydrochloric acid (5:1) to remove alvarolites, followed by the removal of SnO2 with ammonium iodide at 450 ±25℃. The resultant can be taken for the qualitative and quantitative determination of tapiolite. The cassiterite grains ground in the diameter of 1--3mm are repeatedly treated with ammonium iodide to eliminate SnO2, consequently the brown-red alvarolite grains about 1 mm in diameter being visible. After elutriating, the brown-red alvarolite grains are separated from the suspension by means of decantation, followed by the dissolusion of impurities with 10% HOl to obtain the fine-grained alvaralite.The contents of coarse and fine grained alvarolites in cassiterite can be achieved by calculation. Additionally, the quantitative determination has been also carried out on cassiterite sample for the total content of SnO2, quartz, zircon and Nb-, Ta-minerals.

In the present paper the mode of occurenee of niobium and tantalum in cas-siterite has been studied, suggesting that the two elements are present in the form of individual minerals, namely tapiolite (a new mineral), and brown-red coarse and. orange-yellow fine grained alvarolites.The ground sample grains sieved to about 200 mesh are treated with hydrofluoric acid and hydrochloric acid (5:1) to remove alvarolites, followed by the removal of SnO2 with ammonium iodide at 450 ± 25℃. The resultant can be taken for the qualitative and quantitative determination of tapiolite.The cassiterite grains ground in the diameter of 1-3 mm are repeatedly treated with ammonium iodide to eliminate SnO2, consequently the brown-red alvarolite grains about 1 mm in diameter being visible. After elutriating, the brown-red alvarolite grains are separated from the suspension by means of decantation, followed by the dissolusion of impurities with 10% HC1 to obtain the fine-grained alvarolite. The contents of coarse and fine grained alvarolites in eassiterite can be achieved by calculation.Additionally, the quantitative determination has been also carried out on cassiterite sample for the total content of SnO2, quartz, zircon and Nb-, Ta-minerals.