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Four technological samples representing pure and impure dolomitic magnesite deposits, recently explored in the Sul Hamed area, Eastern Desert, Egypt were investigated for their chemical and mineralogical composition. XRD, DTA, DTG. TG and wet chemical analysis methods were applied. Suitability of these deposits for manufacturing shaped and unshaped MgO-CaO refractories was assessed by studying their rate of densification on firing up to 1550 degreesC. The results were interpreted in the light of changes which occurred in phase composition and microstructure of the fired samples. Solid phase composition was qualitatively determined by XRD, where solid and liquid phases coexisting at 1300 and 1550 degreesC were calculated using the available phase equilibrium data. Microstructure and microchemistry of the dense samples were investigated by SEM and EDAX techniques. According to the research output, pure magnesites with the addition of MgO- and/or Fe2O3-rich materials are recommended for the production of unshaped MgO-CaO refractories. On the other hand, impure deposits can be utilized in manufacturing stable and semi-stable shaped MgO-dolomite refractories with and without addition of proper amounts of iron-rich material. (C) 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved.