Characterization of quartzite rocks of the Congo-Nile Ridge in Mugongo-Ryarusera Area, North-West of Burundi

Abstract

The quartzite rocks from the Mugongo-Ryarusera are an important potential resource as they can directly be used industrially. The study aim was to evaluate the physical, petrographic and chemical properties of the Mugongo-Ryarusera quartzite for its value-added uses and industrial applications in glassmaking, ferrosilicon and silicon production. Forty samples were collected and subjected to various analyses. Colour analysis shows that all samples exhibit light colours (white, light grey and very light grey). The evaluation of the density shows an average of 2.64 g/ml which is close to the density value of 2.65 obtained using the specific gravity. The mean porosity value of quartzite rocks of the study area is 3.98 % whereas the particle size analysis shows that the rocks are mostly made up of coarse grains. Petrographic analysis also shows that the quartzite is mainly composed of coarse grains with some fine grains, anhedral to subhedral in many samples. This means that crystals are completely irregular and angular in shape which facilitates an effective melting process. Chemical analysis shows that the mean concentration of SiO2 is about 98.515% and the other oxides include Al₂O₃, Fe₂O₃, WO₃, K₂O, CuO, TiO2, SO₃ and CaO with a mean concentration of 0.681%, 0.2585%, 0.22%, 0.1715%, 0.008%, 0.0095%, 0.034% and 0.00075% respectively. The estimated volume of the outcrop found using GIS (ArcMap) is 11,287,895,590.675 m³ (11.3 km3). Considering the silica content, these rocks can be used for the production of all types of glass, except optical glass, as recommended by the American Ceramic Society and the National Bureau of Standards, as well as by Indian specifications. They can also be utilized for certain types of glass production, as outlined by the British Standard for Glass Sand used in glass manufacturing. Additionally, these quartzite rocks could be used for ferrosilicon production after reducing the average Al2O3 content from 0.6% to 0.4%. However, they are not suitable for silicon production without prior beneficiation. Once impurities are removed by reducing the ratios of trace elements, the quartzite can meet the specifications for all types of glass and silicon production.