Mineralogical study of clays from Dobrodo, Serbia, for use in ceramics

Abstract

This study focuses on the mineralogical characterization of four raw clay samples from Dobrodo deposit, Serbia. Several analytical methods were applied to determine the chemical and mineralogical composition, morphology and physical properties (colour, plasticity, specific surface area, particle size and cation-exchange capacity) of the clay samples. Kaolinite, smectite and illite are the predominant phases in all of the samples studied that contain between 60.2 and 87.1 wt.% of clay. Quartz, feldspars, paragonite and Ti- and Fe-bearing phases were also identified. The relatively high SiO2/Al2O3 mass ratio indicates abundant quartz. The cation-exchange capacity of the samples varied between low and moderately charged clay minerals (12–52 mmol 100 g–1) with specific surface area values ranging from 94 to 410 m2 g–1. The plasticity index values (11–23%) suggest low to moderate plasticity. Preliminary results show that most of the raw clay from Dobrodo deposit might be suitable for use in ceramic applications.

Mineralogical analysis of a clay body from Zlakusa, Serbia, used in the manufacture of traditional pottery

“…The thermal events at ∼350°C and ∼450°C are indicative of iron minerals (goethite and limonite) and halloysite, which are present in smaller amounts (Norton, 1939;Grim & Rowland, 1944). The broad endothermic event at between 550°C and 650°C represents dehydroxylation of kaolinite and halloysite and transformation to amorphous metakaolinite and metahalloysite, but it could also be indicative of illite minerals (Norton, 1939;Speil et al, 1945;Földvári, 2011;Milošević et al, 2019a). The presence of these phases was confirmed by XRPD and SEM analysis.…”

“…The clay in the Dobrodo deposit does not have a uniform appearance and chemical composition. It is layered with clays of various colours and shades, from yellow to dark grey, due to differences in mineralogy (Milošević et al , 2019a).

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“…1.Geographical (left) and geological (right) locations of the investigated samples. Adapted from Milošević et al (2019a). …”

“…According to Djordjević (2013), after mixing of all of the types of raw clays present in the quarry (Milošević et al , 2019a) and removal of aplastic material (pebbles or plants), the clay mix is first immersed in a barrel of water and left to stand in it for the next 24 h. As the excess water is drained, the clay body is extracted onto a table, which will allow for its further preparation and for the addition of calcite. The calcite pieces are first hammered to obtain smaller pieces and then ground in a fine grinding hammer mill, and for the most part, the same particle size is used for all types of vessels.…”

“…The village of Zlakusa lacks the proper raw materials to produce high-quality ceramics and pottery. The raw material instead is delivered from a distance – from the villages of Vranjani and Rupeljevo (Milošević et al , 2019a). It is this careful selection of raw materials that results in the high quality of the pots, which contributed to the survival of this form of pottery despite periods in which demand for it had almost completely ceased.…”