Basalt fiber proponents say that their product clearly outperforms E-glass in composites. In chopped mat, roving and unidirectional fabric forms, basalt fibers exhibit a higher breaking load and higher Young’s modulus (a measure of the stiffness of a given material) than E-glass.

In a study of basalt fibers and E-glass fibers, conducted by Professor Ignaas Verpoest at the Composites Dept. of the University of Leuven in Belgium, unidirectional prepregs were produced by impregnating E-glass and basalt roving with epoxy and winding each on a mandrel, and then compacting the laminate until complete cure was achieved. Samples of 135-mm by 15-mm (5.3-inches by 0.6-inch) were cut and measured for thickness. The pieces were then subjected to a three-point bending test (ISO 178) and the ILSS test (ISO 14130) to test strength and stiffness. Verpoest reports that each sample had a fiber volume fraction of 40 percent, but the basalt/epoxy sample’s strength tested 13.7 percent higher than that of the E-glass sample and exhibited 17.5 percent greater stiffness, although the basalt sample was 3.6 percent heavier than the E-glass sample.

Additionally, basalt fibers are naturally resistant to ultraviolet (UV) and high-energy electromagnetic radiation, maintain their properties in cold temperatures, and provides better acid resistance.

Reportedly, basalt also is superior in the realm of worker safety and air quality as well. Markuts points out that since basalt is the product of volcanic activity, the fiberization process is more environmentally safe than that of glass fiber. The “greenhouse” gases that might otherwise be released during fiber processing, he says, were vented millions of years ago during the magma eruption. Further, basalt is 100 percent inert, that is, it has no toxic reaction with air or water, and is noncombustible and explosion proof.