Weathering tests on kimberlites from several sources indicate that the single most important aspect when considering kimberlite weathering is the presence of swelling clay. Certain kimberlites, containing no swelling clay, are non-weatherable even under considerably aggravated conditions. For other kimberlites, increasing swelling clay content correlates with more severe weathering. The cation exchange capacity (CEC) is a useful parameter that correlates with the swelling clay content; the CEC can be determined relatively fast and economically compared with determination of the swelling clay content by X-ray diffraction.
It has been found that disintegration of kimberlite in contact with water is associated with the swelling of clays (such as smectite). This work investigates the possibility that cation exchange between kimberlite and the aqueous weathering medium could enhance or It is suggested that it may not only be swelling that determines the weathering behaviour of kimberlite but that the cations possibly influence the surface energy.
In the present study we examine the personal belief in a just world for teachers and learners in predominantly Afrikaans-speaking South African schools, and the relationship between teachers' personal belief in a just world and their perception of problem behavior in the classroom. The study is informed by national debates of school violence in South African schools, and international debates on zero-tolerance policies to address school violence. Our findings suggest that teachers' personal belief in a just world predicts their perception of problem behavior in classroom behavior in four areas, namely challenging authority, disrespecting rules and authority and teacher negativity. Teachers with a strong personal belief in a just world were more likely to view classroom behaviours as problematic. Children generally reported that their teachers were fair and just and liked them. However, boys were more likely to have experienced trouble with their teachers and to view them as unfair and unjust. We discuss the significance of the findings in terms of school violence and also mention gendered interpretations to school violence.
Kimberlite is the host rock of diamonds and varies widely in geological, and mineralogical features as well as colour, processing capability and dewatering characteristics. This study investigated the dewatering behaviour of problematic Angolan kimberlites. The presence of clay minerals in kimberlite causes difficulties in dewatering due to high flocculant demand, poor supernatant clarity and low settling rates. Identifying critical parameters governing the settling behaviour will assist in managing the settling behaviour of different kimberlite slurries. The influence of particle size, pH of the kimberlite slurry, cation exchange capacity, exchangeable sodium percentage and smectite content of the kimberlite on the settling rate were investigated for 18 different African kimberlite samples. The settling rate and slurry bed compaction during natural settling were also measured for the kimberlite slurries. Seventeen different Angolan clay-rich kimberlites and one South African clay-rich kimberlite were tested and, except for two kimberlites, colloidal stability was experienced during natural settling. The pH values of the kimberlite slurries ranged between 9 -11, which is similar to the pH band where colloidal stability was found during earlier research.
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