CLAY SOILS IN MCHINJI: POTENTIAL RAW MATERIALS FOR CERAMIC INDUSTRY

Mchinji district is composed of a thick layer of superficial deposits which include vast dambos, colluvium, and alluvial plains with aplenty clay soils in their numerous valleys. Regardless of its high proportion, clay soils from Mchinji are only exploited for conventional pottery and local ceramic bricks. This is basically because the potentialities of these clay soil have not been evaluated. Up to the present moment, no study that evaluates the potential applications of these clay soils is available.
Ceramic suitability of clays in the selected sites of Mchinji was assessed utilizing empirical diagrams, involving grain size distribution, and chemical composition and by adopting a new approach basing on the methodology of the experimental design. It is found that the particle size distribution contains higher percentages of sand fractions, followed by clay fractions, and the lowest being silt. The chemical composition was found by XRF analysis which showed higher percentages of SiO2, Al2O3, and Fe2O3. The low content in a fluxing agent is indicated by the low contents in Na2O, K2O, MgO, TiO2, CaO, MnO, and P2O5.
The Mchinji clays are distributed in sandy clay loam and sandy clay in the grain size distribution diagram. These clays have ceramic suitability of checker bricks (perforated bricks) and clay roofing tiles. Taking into account the chemical composition, the clays have the suitability of red stoneware.

Mchinji district is composed of a thick layer of superficial deposits which include vast dambos, colluvium, and alluvial plains with aplenty clay soils in their numerous valleys. Ceramic suitability of clays in the selected sites of Mchinji was assessed utilizing empirical diagrams, involving grain size distribution, and chemical composition and by adopting a new approach basing on the methodology of the experimental design. It is found that the particle size distribution contains higher percentages of sand fractions, followed by clay fractions, and the lowest being silt. The low content in a fluxing agent is indicated by the low contents in Na2O, K2O, MgO, TiO2, CaO, MnO, and P2O5.

Mchinji is located northwest of Bua River and is almost entirely underlain by the gneisses, granulites, quartzites, and schist of the basement complex. The basement complex is overlain by thick superficial deposits that include residual soils, alluvium, and colluvium (Thatcher & Wilderspin, 1968). Exposures of the basement complex are poor being restricted to the mountain ranges and a few small outcrops along streams or banks of dambos. The rocks are either fine-grained or coarse-grained. The fine-grained type is a source of the silica sands found in the dambos (Malunga, 2014). Mchinji sands are fine to very fine-grained and appear to be almost completely composed of quartz grains. In some parts, very small amounts of black minerals and iron oxides, and muscovite flakes can be observed.
Mchinji soils are classified as ferrallitic soils, weakly ferrallitic soils, ferrallitic with laterite and lithosols (Chinyama & Lowole, 1983). Ferrallitic soils are somewhat highly weathered, yellowish-red, or brown loamy structureless (Massive) soils, low inherent potential and are widely prevalent. Weakly ferrallitic soils are somewhat highly weathered, red, loamy, or clayey soils with some ferruginous property. Ferrallitic with laterite soils is massive laterite that occurs 100 centimeters from the surface. Lithosol is shallow and is mostly gravelly soil.

District: Mchinji

Coordinates: -13.77835, 33.0224