In this paper the chemical composition and properties of briquettes from combustible slates is studied during the heat treatment, made of waste of a slate field of the Leningrad region. Formation of a large amount of ashes is the main problem connected with processing and use of combustible slates. The component structure of mineral part of slate is revealed. Change of mass of combustible slate at heat treatment in the range of temperatures 25- 950°C is defined. Reduction of mass of slates happens during five cycles about change of structure and physical and chemical properties. The analysis of allocations of gas components condensed in water solution during heat treatment showed that at increase in temperature Ã‘Â€ÃÂ environment decreases with 6,72 to 6,31 and P2O5, SO3 are allocated. Also in the form of a suspension at solution there are Al2O3, SiO2, CuO, ZnO, MgO. Studying of structure and physical and chemical properties of briquettes from combustible slates during heat treatment gives the chance to define the periods of devolatilization of coal and coking of samples.