Portland cement could be produced by heating the raw materials (clay, lime stone) about 1500°C which clinker will be formed. The geochemistry and mineralogical studies of raw materials, clinker, Portland cement and dust have been carried out by optical microscopy, X-ray diffraction and X-ray florescence. The results of spectrometry indicate the presence of calcite mineral in limestone, montmorillonite, quartz, calcite, albite, muscovite, hornblende, orthoclase and chlorite minerals in clays, hematite minerals in ironstone, quartz, plagioclase, tourmaline minerals in siliceous materials and gypsum in gypsum rock. ‍‍‍Calcite is the main mineral and quartz, muscovite –illite and chlorite are the minor minerals in the dust of the furnace of the Neka cement factory. The mineralogical study of clinker indicates the presences of calcium silicates and brown millerit minerals, while gypsum, larnit, brown millerit and calcite minerals are indentified in Portland cement. calcium silicates (tricalcium silicate and dicalcium silicate), and larnit are the main minerals and Gypsum and brown millerite (tetracalcium aluminoferrit) are the minor minerals of the dust in the mill of the Neka cement factory. In phase system diagram (CaO-Al₂O₃-SiO₂), chemical components limestone and clays occur in carbonate rocks and tridymite respectively, While clinker and Portland cement occurred in C3S-C2S-C3A triangular. According to Bogue equation, this clinker and Portland cement coincide with international standard of cement.