Mineralogical and geochemical suitability of some Egyptian raw materials for the production of magnesio-aluminosilicate ceramics

Abstract

The talc rocks are considered as important resources for the magnesium oxide ceramics. The talc rocks are mainly quarried at the Eastern Desert, therefore, selected areas were the main target to study the petrography, geochemistry and industrial applications of the outcropped serpentinites and their derivatives. The study target areas are Wadi Abu Fannani, Wadi Mubarak, Gabal Hijllij, Gabal Um Salatit, Wadi Barramiya, Gabal Mudargag, Wadi Antr, Wadi Nukharia and Wadi Allaqi.

The rocks of the ten areas are distinguished with different grades of talc rocks. Petrographically, the rocks of Wadi Allaqi are considered as pure talc whereas Wadi Mubarak is dominated by talc-tremolite rocks. Geochemically, the serpentinites and talc rocks represent the following geochemical features: (a) the serpentinites have considerable values of SiO2 (36.29 – 42.28 wt.%) and MgO (29.06 – 41.27 wt.%) which might refer to a developed magma of mantle composition; (b) talc rocks show high percentages of SiO2 (up to 74.25 wt.%) and depleted values of MgO (3.79 – 32.54 wt.%) due mainly to alteration processes (such as silicification and carbonation). Seven areas are considered promising for cordierite-based ceramic production. These areas are Abu Fannani, Wadi Mubarak, Gabal Hijllij, Gabal Um Salatit, Wadi Antr, Wadi Nukharia and Wadi Allaqi. The talc samples of these areas were mixed with high grade kaolin selected from Southern Sinai. This mix design for all nine representative talc samples is based on the stoichiometric cordierite composition. The synthesized cordierite ceramics contain crystalline and amorphous phases with mutual relations to affect their characteristics. The chemical composition of the whole nine batches encourages their solid-state reaction upon sintering in the temperature range between 1000 and 1375