Micro- and Nanotexture and Genesis of Ball Clays in the Lower Cretaceous (SE Iberian Range, NE Spain)

Ball clay deposits in the SE of the Iberian Range (NE Iberian Peninsula) consist of Albian clays and siltstones with greyish and blackish colors, interbedded with subbituminous coals. The ball clays are nowadays mined for the manufacture of white color ceramics. The mineralogy of these deposits consists mainly of kaolinite, illitic phases, and quartz. The euhedral to sub-euhedral morphology of the kaolinites suggests their in-situ origin. The anhedral morphology of the illites and the presence of frayed illites suggest a detrital origin. At the micro-scale, authigenic kaolinite booklets are observed filling pores and forming mica/kaolinite intergrowths, in which the kaolinite grows between the cleavage sheets of pre-existing detrital mica. At nanometer scale, illite/smectite (IS) phases are detected forming interlayers with mica and kaolinite, and evidence of the replacement of mica by kaolinite is observed. The matrix consists of defective illite and kaolinite, and random mixed layers of kaolinite-I/S (Kln-IS), illite-I/S (Ilt-IS), and I/S-smectite (IS-S). The textures of illite and the presence of different types of mixed layers suggest that the expandable phases and kaolinite are products of mica alteration. The effectivity of the alteration was probably a consequence of the low pH that occurred in the environment due to the presence of abundant organic- and acidic- rich fluids.

Maceral Association in Coal-bearing Formation of Mae Than Coal Mine in Lampang, Thailand - Implication for Depositional Environment

The Mae Than Basin in Lampang Province contains low-ranked coal reserves of northern Thailand. Coal seams and ball clays were mined in the southern part of the basin. This study focuses on the coal petrography of coal samples collected from the upper coal seam in the Mae Than Coal Mine. Both the organic and inorganic constituents provide information on the nature and characteristics of the coal, reflecting the physical and chemical behaviors of coal. Petrological analysis reveals that the Mae Than coals contain more huminite than liptinite macerals, while inertinite is negligible. Huminite occurs mainly in the form of texto-ulminite, textinite, densinite, and gelinite. Liptinite consists of sporinite, cutinite, resinite, suberinite, liptodetrinite, and terpenite. The morphology of cutinite, sporinite, and the presence of terpenite indicate that the peat-forming vegetation may consist of conifers. In addition to the macerals, the coal samples contain a small to moderate amount of mineral matter. Silica and clay minerals are the main minerals found in the cavities and between the cracks of the coals. The assemblage of macerals and mineral matter indicates that the Mae Than coals were formed mainly from common peat-forming vegetation, possibly conifers, in a freshwater forest swamp or mire in a warm temperate climate. In addition, the high degree of preservation of the macerals indicates a high water table and suggests rheotrophic, anoxic, limnotelmatic to telmatic conditions during deposition.

Effects of Bituminous Coal Ash Addition in Pottery Products

Bituminous coal ash, fly ash (FA) and bottom ash (BA), from coal power plant were studied in this research for utilizations in ceramic and pottery industries. Both fly ash and bottom ash mixed with four different ball clays from two kinds of ceramic pottery products such as flowerpot and construction brick, Ratchaburi, Chantaburi, Angthong and Chonburi ball clay. The mixtures were varying ratio between ashes and clays depend on clay sources. After mixing, the bodies were formed to test pieces and were then fired at 800-1200 °C. The results indicated that, added fly ash 0-40 wt% significantly decreased water absorption and increased bending strength when fired at 1150 °C or above. For color effect, CIE L*a*b* color space, both fly ash and bottom ash revealed the samples less lightness, more red and yellow appearance. These results are obvious when fired at 1150oC or above. Following the results, fly ash is possible to be used in ceramic pottery industries replaced with other addition such as sand and pottery stone.

Estudo de novas ocorrências de argilas plásticas (ball clays) do nordeste do Brasil para uso em cerâmicas refratárias

Resumo A região nordeste do Brasil possui grandes depósitos de argilas plásticas do tipo ball clay situados geralmente na Formação Barreiras e são usados em cerâmica branca e materiais refratários. Essas argilas são constituídas por caulinitas secundárias e matéria orgânica, sendo muito plásticas e quando submetidas a elevadas temperaturas queimam com cores brancas e ocorrem transformações de fases, principalmente formação de cristais de mulita e cristobalita. Este trabalho tem como objetivo estudar novos jazimentos de argilas plásticas visando utilizá-los na produção de materiais refratários. As argilas foram caracterizadas por difração a laser, difração de raios X (DRX), fluorescência de raios X, refratariedade, análise térmica e microscopia eletrônica de varredura (MEV). Os corpos de prova foram prensados e sinterizados a 1000, 1150, 1250, 1280 e 1400 °C. A caracterização após queima foi realizada por DRX e MEV. Em seguida foram determinadas as propriedades físico-mecânicas: absorção, porosidade e tensão de ruptura à flexão. Os resultados evidenciaram que as argilas apresentaram a formação de cristais de mulita com propriedades físicas, químicas e mineralógicas adequadas para uso em cerâmica refratária.

Occurrences of kaolin in Koutaba (west Cameroon): Mineralogical and physicochemical characterization for use in ceramic products

Thirty clay samples collected from three hills in Koutaba (west Cameroon) were characterized in order to evaluate their potential use as raw materials for ceramics. After preliminary mineralogical identification by X-ray diffraction, three representative samples from the three different hills, referred to hereafter as K1M, K2M and K3M, were selected for further investigation by X-ray fluorescence, plasticity, granularity and thermogravimetric analysis. The main clay minerals are kaolinite (32–51%) and illite (up to 12%). Additional major phases are quartz (32–52%), goethite (6–7%) and feldspars (0–4%). The chemical composition showed variable amounts of SiO2(60–72%), Al2O3(15–20%) and Fe2O3(1–9%), in accordance with the quartz abundance in all of the samples studied. The particle-size distribution showed a large proportion of silty fraction (64–88%) with moderate sandy (9–19%) and clayey fractions ( < 5% for K2M, 12% for K1M and 20% for K3M). All of the clays showed moderate plasticity-index values (8–11%). Because of these characteristics, K1M and K3M may be suitable for use in common bricks and hollow ceramic products. Sieving or the addition of ball clays is recommended to increase the plasticity of sample K2M for use in common bricks.

THERMO GRAVIMETRIC AND DIFFERENTIAL THERMAL ANALYSIS OF CLAY OF WESTERN RAJASTHAN (INDIA)

The paper presents the study of thermo gravimetric and differential thermal analysis of blended clay. Western part of Rajasthan (India) is rich resource of Ball clays and it is mainly used by porcelain, sanitary ware, and tile industry. The quality and grade of clay available in the region vary from one deposit to other. To upgrade the fired colour and strength properties, different variety of clays may be blended together. The paper compares the results of thermal analysis one of blended clay B2 with reference clay of Ukraine which is imported by industries owners. The result revealed that the blended clay is having mineral kaolinite while the Ukrainian clay is Halloysite.