Windblown transport and deposition of dust is widely recognized as an important physical and chemical concern to climate, human health and ecosystems. Sistan is a region located in southeast Iran with extensive wind erosion, severe desertification and intense dust storms, which cause adverse effects in regional air quality and human health. To mitigate the impact of these phenomena, it is vital to ascertain the physical and chemical characteristics of airborne and soil dust. This paper examines for the first time, the mineralogical and chemical properties of dust over Sistan by collecting aerosol samples at two stations established close to a dry-bed lake dust source region, from August 2009 to August 2010. Furthermore, soil samples were collected from topsoil (0-5 cm depth) at several locations in the dry-bed Hamoun lakes and downwind areas. These data were analyzed to investigate the chemical and mineralogical characteristics of dust, relevance of inferred sources and contributions to air pollution. X-Ray Diffraction (XRD) analysis of airborne and soil dust samples shows that the dust mineralogy is dominated mainly by quartz (30-40%), calcite (18-23%), muscovite (10-17%), plagioclase (9-12%), chlorite (~6%) and enstatite (~3%), with minor components of dolomite, microcline, halite and gypsum. X-Ray Fluorescence (XRF) analyses of all the samples indicate that the most important oxide compositions of the airborne and soil dust are SiO 2 , CaO, Al 2 O 3 , Na 2 O, MgO and Fe 2 O 3 , exhibiting similar percentages for both stations and soil samples. Estimates of Enrichment Factors (EF) for all studied elements show that all of them have very low EF values, suggesting natural origin from local materials. The results suggest that a common dust source region can be inferred, which is the eroded sedimentary environment in the extensive Hamoun dry lakes lying to the north of Sistan.

HOW TO CITE:Morekhure-Mphahlele R, Focke WW, Grote W. Characterisation of vumba and ubumba clays used for cosmetic purposes. S Afr J Sci. 2017;113(3/4) FUNDING:Tshwane University of Technology Two traditional cosmetic clays bear similar names in different local South African languages: vumba (Tshivenda) and ubumba (isiZulu). The wet clays are applied topically for cosmetic purposes by the respective indigenous peoples. Six samples from two South African provinces were characterised using X-ray diffraction, X-ray fluorescence spectroscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis and scanning electron microscopy. It was found that the samples differed widely with respect to mineralogy and chemical composition. This finding raises the possibility that texture characteristics during application on the skin override composition effects. Of concern is the high levels of quartz found in all the samples as it might pose a health hazard; the lowest value for quartz was 11 wt% for vumba, while values for ubumba ranged from 26 wt% to 85 wt%. All samples contained varying amounts of silicates in the form of smectite, kaolin, chlorite and plagioclase. Minor amounts of anatase and rutile were present in some samples. Three samples also contained goethite. All samples were essentially free from the toxic elements As, Pb, Hg, Cd, Se and Sb. However, they did contain low levels of chromium and heavy metals such as Cu, Zn and Ni. The pH values of ubumba slurries were slightly basic, while those of a vumba slurry were slightly acidic. Significance:• Wide ranges of composition appear to be acceptable.• The clays do not contain highly toxic or radioactive elements.• The high levels of quartz present may pose a human health risk.

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Gold-rich alloys with variable ¡imounrs of Pd from the Merensky Reef, Bushveld Complex, are charatterized by a range of finely dispersed inclusions. The small sizes of these inclasions (median of 1,85 fJLin) make fiilly quantitative analyses virtually impossible. Tentative interpretation of semi-quantitative microprobe analyses demonstrates the presence of atokite. kotulskite, laurite, moncheice, niggliite, paolovlte, rustenburgite, sobolevskite, and spenylite. Some inclusions appear to represent unnamed minerals.Textures and assemblages imply that these gold grains and their inclusions formed from Huids through occasional remobilisation and co-precipitation.

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