Minerals and Metals in Ancient India v1.c14.s5: Clay
Minerals and Metals in Ancient India v1.c14.s5
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Clay
v1.c14.s5.1
The natural soil available in the flood plains around Lothal is alluvial clay mixed with small quantities of mica. Below this deposit is a thick layer of whitish kankar. The alluvial clay is capped by a deposit of sticky black clay which is used nowadays for pottery making. Mica, sand and lime occurring in small quantities as natural impurities acted as degraissants for tempering earthen wares. However in the case of coarser wares, sand, lime and chaff were deliberately added to counteract the plasticity of black clay for producing a porous and gritty surface. The use of chaff in clay for producing red and coarse grey wares is evident from the smoky core and pitted surface and section of the vessels. Occasionally animal-dung was also used as a degraissant. (Rao, 335)
v1.c14.s5.2
Pottery samples were chemically analysed and found to contain high proportions of not only SiO₂, Fe₂O₃, and Al₂O₃, but also CaO, MgO and CO₂. This proved that calcareous clay was used for making potteries.