Ceramics were one of the oldest and most important industries that had evolved significantlyall over the Islamic periods. Jar is a large ceramic vessel that was used in the Islamic period.It was excavated at Al Fustat, Egypt by the Faculty of Applied Arts, Helwan University andwas added to the college museum in 1945. It was found that it dated back to the MamlukPeriod (1250–1517A.C.). The jar was in a very poor condition; it was fielded and was restoredwith unsuitable materials that turned it into several parts, especially at the base. In addition, itsuffered from many deteriorations that include cracks, decay and crystallization of salts.Furthermore, many shards were broken from the body and some were missed. The aim of thecurrent study was to study and restore the chemical and mineralogical composition of the claybody, the glaze and the crystallized salts. Different analytical methods were used including; Xraydiffraction (XRD) and Scanning electron microscopy (SEM) coupled with energydispersive X-ray spectroscopy (EDS). Chromite (Cr2O3) was used to obtain green glazes.Different restoration treatments were carried out on the jar, such as mechanical and chemicalcleaning, consolidation, bonding and replacement processes. The results suggested that thesalt was made of Halite mineral (Sodium chloride) and Calcite (CaCO3), while the clay body ofthe jar was made of ferruginous, highly calcareous clay in an oxidizing atmosphere.Additionally, minerals such as silica, hematite, gehlenite and lime were identified.