3.1 Morphological features of tailing profiles
Mining activities drastically altered soil morphological features (Figures S1 and S2). In tailing derived from sandstone materials, tin mining activities altered the soil morphological features from sandy clay loam texture, dark brown topsoil and yellowish brown subsoil in native soil (TBB4 profile) to sandy texture with stratification of light grey and yellowish grey (TBB1) or of yellowish grey and reddish grey (TBB2) colour throughout profiles (Figure S1). Further, a spoil profile with a mixture of native topsoil and sandy tailing showed a mixture of brown and greyish colours in the topsoil (TBB3 profile), which was underlain by greyish sand and whitish kaolin colours. The presence of yellowish and reddish colours in sandy tailing profiles indicated the initiation of soil formation in post-tin mining areas.
For post-tin mining soils developed from granite parent materials, morphological properties drastically altered from deep solum (> 140 cm), dark greyish brown topsoil and yellowish brown subsoil with sandy clay loam texture (TBB5; Figure S2) in the native soil to loamy sand and grey colour in post-tin mining. These native soil properties disappeared after mining was related to sluice and washing during the separation of heavy tin ore from light sand fractions. The profile of a sandy tailing (TBB6), which has been reclaimed for 26 years using Acasia mangeum  started a weak soil development as indicated by yellowish colour (iron mobilization and precipitation), the formation of fine soil granular structure, and the growth of many fine roots downward to 60 cm deep (Figure S2). Unfortunately, the formation of fine soil granular structure was not shown by TBB7 profile, a counterpart of TBB6 and just 6 m away. The absence of fine soil granular structure in the TBB7 profile was due to re-mined activities by local traditional miners and abandoned as bare land by 2008 (8 years old of post tin mining), leading to reset back the new start of soil development. The interlayer variations with different colours within a profile indicated the initial accumulation of iron with yellowish grey colour (probably goethite) and it’s leaching down the profile.