The Karatau basin includes dozens of phosphorite fields which are distinguished both in chemical composition and in mineralogy. The main factors which influence the technological properties of the ores are chemical-mineralogical composition and structural-textural features of the phosphorites. Changes are examined in the physical chemical properties during thermal treatment of phosphorite of the Dzhanats field, northwest section. It was established as a result of the studies that the sample of phosphorite of Dzhanatas of the northwest section contains 3 main components: phosphate substance, silica and carbonates. Of the mineral admixtures, oxides and hydroxides of iron, alumosilicates, mica and organic substance are present. In the dominance of a certain mineral, the northwest section belongs to the silicon-phosphatecarbonate type.