Mineralogy and Geochemical Characteristics of Matamba Kaolin Deposit-Njombe Region South-Western Tanzania: Implications for Industrial Applications

Abstract

Kaolin is a commercial clay material composed of hydrated aluminosilicate mineral kaolinite and used in various industrial applications such as ceramics, paper, paints, refractories, fiberglass, plastics, cosmetics and pharmaceuticals. It is formed as a result of strong chemical weathering of crystalline and feldspar-rich rocks or hydrothermal alteration of granitic rocks at relatively low temperature and pressure conditions. The kaolin deposit of Matamba originated from the weathering of leucogabbro rock during the development of the African land surface. In view of highlighted properties, the mineralogy and chemical characteristics of the Matamba kaolin deposit were investigated to determine its industrial applications. As part of the study approach, forty-six (46) samples were collected and analyzed for major oxides using X-ray fluorescence (XRF) and mineralogical composition using X-ray diffraction (XRD). The XRD results indicated that the Matamba kaolin is dominantly composed of kaolinite (10.1–100%) with other phases such as albite (1.2–56.8%), oligoclase (10.1–54.3%), quartz (1.2–33.9%), goethite (1.0–9.4%) and muscovite (1.1–29.5%). The dominant major oxides are SiO2 (39.78–67.96 wt.%), Al2O3 (14.60–38.07 wt.%) and subordinate amounts of Fe2O3 (0.93–6.37 wt.%), MgO (1.42–4.74 wt.%), Na2O (0.10–1.09 wt.%), K2O (0.14–2.01 wt.%), CaO (0.08–0.99 wt.%), TiO2 (0.07–1.66 wt.%), P2O5 (0.36–1.77 wt.%) and LOI (1.91–13.97 wt.%). These major oxides correlate with the mineralogical composition supporting kaolinite dominance. Consequently, compared with some industrial specifications, these results indicate that Matamba kaolin deposit may be useful for ceramic products, refractories such as fireclay crucibles and electrolytic production of aluminium and its alloys. However, it should be beneficiated and upgraded to improve some technical properties to qualify for other industrial applications.