Basalt fibers are produced from basalt rocks by melting them and converting the melt into fibers. Basalts are rocks of igneous origin. The main energy consumption for the preparation of basalt raw materials to produce of fibers is made in natural conditions. Basalt continuous, staple and super-thin fibers are produced and used. Basalt continuous fibers (BCF) are used for the production of reinforcing materials and composite products, fabrics and non-woven materials. Basalt staple fibers - for the production of thermal insulation materials. Basalt superthin fibers (BSTF) - for the production of high quality heat and sound insulating and fireproof materials. Manufacture The technology of production of basalt continuous fiber (BCF) is a one-stage process: melting, homogenization of basalt and extraction of fibers. Basalt is heated only once. Further processing of BCF into materials is carried out using "cold technologies" with low energy costs. Basalt fiber is made from a single material, crushed basalt, from a carefully chosen quarry source. Basalt of high acidity (over 46% silica content) and low iron content is considered desirable for fiber production. Unlike with other composites, such as glass fiber, essentially no materials are added during its production. The basalt is simply washed and then melted. The manufacture of basalt fiber requires the melting of the crushed and washed basalt rock at about . The molten rock is then extruded through small nozzles to produce continuous filaments of basalt fiber. The basalt fibers typically have a filament diameter of between 10 and 20 μm which is far enough above the respiratory limit of 5 μm to make basalt fiber a suitable replacement for asbestos. They also have a high elastic modulus, resulting in high specific strength—three times that of steel. Thin fiber is usually used for textile applications mainly for production of woven fabric. Thicker fiber is used in filament winding, for example, for production of compressed natural gas (CNG) cylinders or pipes. The thickest fiber is used for pultrusion, geogrid, unidirectional fabric, multiaxial fabric production and in form of chopped strand for concrete reinforcement. One of the most prospective applications for continuous basalt fiber and the most modern trend at the moment is production of basalt rebar that more and more substitutes traditional steel rebar on construction market. Properties The table refers to the continuous basalt fiber specific producer. Data from all the manufacturers are different, the difference is sometimes very large values. Comparison: