Bulletin of the Geological Society of Malaysia, Volume 53, June 2007, pp. 125 - 128
Geology Department, University of Malaya, 50603 Kuala Lumpur, Malaysia
Abstract: The heavy minerals from tin tailings or amang comprises a wealth of minerals which contain some of the most sought after metals in industry that includes tantalium and niobium, which are widely used in the computer and cellular phone industry because of their high reliability, high melting points and corrosion resistance characteristics. An extended investigation was carried out on the EPMA (Electronprobe Microanalyzer) into the complex nature of strüverite, the source of tantalium (Ta) and niobium (Nb) in amang, in particular its complex mineralogy, chemistry and associated phases/minerals. EPMA data of strüverite show that it is a complex intergrowth of rutile (TiO2), tantalite (Ta2O5) and columbite (Nb2O5) with only very few grains devoid of any inclusions or exsolved phases. EPMA analysis of three “pure” strüverite grains, devoid of intergrowths, gave consistent ratios of Ti (19.58–29.08 wt%), Nb (5.45–7.99 wt%), Ta (25.43–33.46 wt%) and Fe (6.89–8.11 wt%). They also contain significant amounts of Sn (0.79–2.62 wt%) and Th (3.25–6.03 wt%) but very low W (0.11–0.47 wt%) and Mn (0.01–0.12 wt%) and no Y. Other strüverite grains which have inclusions or exsolved phases or intergrowths, all show very variable contents of Ti, Nb, Ta, Fe, W, Mn, Th and Y. BSE (backscattered secondary electron) images on the EPMA also picked up zoned strüverite crystals where great variations in compositions are clearly discernible in X-ray maps of these zoned crystals. EPMA analysis of fusion discs of strüverite concentrates from amang also show quite variable contents for Ti (12.60–54.38 wt%), Nb (1.71–13.12 wt%), Ta (2.88–7.40 wt%), Fe (1.43–15.65 wt%), W (0–3.48 wt%), Mn (0.05–1.51 wt%) and Th (0–29.76 wt%). The presence of Th with or without Y in some strüverite grains could be a useful criteria for determining their source area. Knowledge of the complexity of strüverite is useful in configuring the correct recovery processes for Ta and Nb.