The growing requirements for and growth of production of mullite-silica composition glass fiber materials and parts of them requires broadening of the raw material base. At present for production of mullite-silica fiber materials the majority of leading foreign firms in this area and the USSR use artificial mixtures of alumina and silica [I]. As a rule quartz sand or flint Cleansed of coarse inclusions and dried to a residual moisture of 1-2% is used as the silica constituent [1-3].Preparation of quartz sand for use does not involve significant energy and economic expenditures while the alumina used is a material distinguished by a high energy requirement and production complexity.In connection with this at present alumina is a material in short supply, the requirement for satisfying the needs of the national economy increases each year and therefore the use of natural aluminosilicates as original material for production of glass fiber materials is of great interest.Abroad natural minerals of kaolin composition* are used for these purposes and there is information on compositions of more than 60 compounds from which fiber composite materials are produced.An obligatory condition is an AI203/SiO 2 ratio of 3/2.The production operation of refractory glass fibers includes the following operations: preparation of the original materials; fusion of the charge; discharge of the molten aluminosilicate as a stream of constant cross section and flow; dispersion (spraying) of the stream of molten material into individual fibers by the energy carrier (steam or compressed air); cutting of the fiber mat formed into the necessary size; rolling up of the rolls; packing of the finished product.In production of glass fiber materials from mixtures of alumina and quartz sand and also from natural aluminosilicates the production method does not change but the process of melting of natural aluminosilicates has a number of peculiarities.In heating of alumina the basic form of it, y-alumina, changes irreversibly into ~-AI203.According to the data of various authors the temperature of this transformation varies from 600-950 to 1450~Alumina of the m-form is a phase stable at all temperatures and is an analog of a natural mineral, corundum.The melting point of ~-AI20 m is 2040-2050~[4]. The primary constituent of quartz sand is quartz, which, as a rule, in heating transforms into cristobalite at I050-1450~At normal pressure melting of quartz starts at the grain boundaries and spreads into the depth of the crystal.At high melting temperatures silica is significantly volatile, especially under conditions of reducing media.In evaporation silica partially dissociates with formation of silicon monoxide (SiO), which is carried from the melting furnace by the gas flows. A portion of the silicon monoxide in metastable form precipitates on the electrodes in the solid phase. Above 1010~ the existence of SiO is probable while at lower temperatures SiO decomposes with formation of silicon and silica [5].In heating of natural aluminosilicates dehydratio...