3.2 Mineralogical composition of tailings
Mineralogical composition of soils at post- tin mining areas was
assessed to get an idea of potential inherent nutrient source and heavy
metals in weathereable minerals (host-nutrients). Tailings and native
soils developing from sandstone contained 70-95% and 81-84% quartz,
respectively (Table 1). The corresponding values for tailings and native
soils developed from granite were lower, namely 48-73% and 77-80%,
respectively. In native soils (TBB4 and TBB5 profiles), the turbid
quartz was higher than transparent quarts, irrespective of parent
material types, indicating transportation was a dominant process during
soil formation.
In contrast to quartz mineral, the tourmaline mineral was considerably
higher in tailing deriving from granite (12-22%) than tailing from
sandstone (2-10%). The corresponding values in native soil profiles
were 5-7% and 2-3%, respectively. Both quartz and tourmaline minerals
are well known as mineral resistant to weathering. Opaque mineral was
also higher in tailing derived from granite (mostly 9-15%) than tailing
from sandstone (1-7%). Further, the tailing profiles deriving from
granite (TBB6 and TBB7) contained a small number of orthoclase and
sanidine, which were absent in tailing profiles from sandstone (TBB1 and
TBB2). Other minerals in small amount were zircon, garnet, epidote and
rutile/anatase in all tailings and native soils.