3.4 Characteristics of tin ores and white clay spoil
Properties of tin-host minerals and white clay were assessed using scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses. The large ore grain of tin (Figure 1a) showed a fresh, clean and smooth surface with elongated grain shape and euhedral crystal edges. The EDX surface chemical composition analysis showed the presence of triple peaks of Sn in the order of decreasing intensity at 3.45, 3.70 and 3.90 KeV, and another Sn peak at 0.5 KeV, indicating the Sn-bearing grain is cassiterite (Sn02) mineral (Figure 1c). Further, the XRD analysis of the ore grains indicated the presence of three very sharp and slender peaks in the order of decreasing intensity at 3.33, 2.63, and 2.36 Å, confirming the very well crystal structure consisting of cassiterite mineral (Figure 1d). Therefore, the tin ores in this study consisted of mainly cassiterite mineral.
In Bangka, some of the spoils showed greyish white colour with fine texture and sticky consistency, while information of its mineral composition was not available. Hence, it is necessary to examine the mineral constituent of whitish clay and its relation to management as crop media with respect to reclamation measures. The XRD analysis showed the presence of prominent sharp and slender peaks at 7.15 and 3.57 Å, accompanied by less peak intensity at 4.47, 2.56, 2.49, and 2.34Å (Figure 2), indicating the kaolinite mineral. There is also evidence for the kaolinite impurity due to the presence of goethite in the mineral, which is shown by XRD peaks at 4.16 and 2.19 Å. The SEM showed the micro-pores occurring within kaolinite layer arrangement, which are able to store water (data not shown).