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).