A lightweight heat-insulating building material which has excellent frost resistance and a low price is provided. Pure silicon is produced from sand using solar energy. One side of the conductive core is provided with a dielectric laminate, a portion of which flows into and coats the core through hole wall. As a result, the invention provides a significant reduction in the total cost of operating a Bayer process. The mounting device further includes at least one rail for protecting the lens portion from damage. The downward disc fan thrust causes additional lift.