Investigation of Oğlakçı and Kurtşeyh Sepiolites (Eskişehir, Türkiye): As Common Clay Alternatives and Possibilities of Use in Terms of Ceramic Tile Production

The primary source of clay for ceramic producers in Turkey has historically been the clay extracted from the Şile region and imported from Ukraine. However, the depletion of existing resources and the increase in logistics costs have prompted the sector to explore alternative raw materials. In this context, the stratified sepiolite deposits in Sivrihisar region (Eskişehir, Türkiye) have garnered attention. While these deposits have been utilized in industrial applications, such as cat litter and exported overseas, since the 1970s. The limited physico-chemical properties of sepiolite clay have precluded sufficient investigation into its use in ceramic recipes to date.

Sepiolite formations have been identified within the sedimentary succession of Sakarya Formation Miocene in age. Sepiolite formation is believed to have been sourced from ophiolites, Paleocene-Eocene aged granitoids and marbles. The mineral deposits, which were formed in the lacustrine basins that emerged during tectonic movements, have been converted into sepiolite and dolomite sepiolite deposits in both alkaline and salty environments. However, the absence of lateral continuity in these deposits suggests that their economic viability may be constrained.

This study aims to investigate the potential application of sepiolite and dolomite sepiolite deposits in the Kurtşeyh and Oğlakçı regions of Sivrihisar in the production of wall and floor tiles. The methodology includes geological mapping in both regions, the preparation of stratigraphic sections, and systematic sampling together with the chemical, mineralogical and technological analysis. Geological observations indicate that the sepiolite succession occur in three distinct forms: as pure sepiolite, sepiolite-bearing dolomite, and dolomite-bearing sepiolite. XRD analysis revealed the raw materials to consist of sepiolite ± dolomite ± calcite ± montmorillonite ± palygorskite ± organic ingredients. XRF analysis indicated the prevalence of CaO, SiO₂, and MgO in these clays, with components such as Al₂O₃ and Fe₂O₃ being secondary.

In the laboratory, the thermal properties of the samples were investigated through the application of firing processes. Wall tiles were produced through a 40-minute firing process at 1125°C, while floor tiles underwent a 67-minute firing process at 1185°C. The technological properties of the materials, including density, shrinkage, water absorption, dry strength, and color, were evaluated. The results obtained demonstrated that sepiolite, particularly dolomite sepiolite, can be utilised as an alternative for Istanbul (Şile) and Ukraine clays in ceramic formulations. The adding of 10% of sepiolitic clays into the ceramic mixture exhibited performance that was commensurate with standard production processes.

In conclusion, sepiolite and dolomite sepiolites have been identified as a potential alternative raw material for the ceramic industry in the Kurtşeyh and Oğlakçı regions of Sivrihisar. However, further detailed field studies and industrial-scale trials are required to ensure economic and logistical sustainability.