<p>A brush bristle material comprising a linear metallic material containing powders of one or more kinds of lava abrasive grains and/or basalt abrasive grains in a mixed state at a ratio in the range of 1% to 70%, preferably in the range of 1% to 30%. The powders of the lava abrasive grains and/or the basalt abrasive grains to be included in the linear metallic brush bristle material are incapable of being burnt and melted during the course of the inclusion and capable of enhancing the ability of grinding or abrading. Therefore, it is made possible to optimize the surface treatment of the interior of a hole in a given workpiece and the removal of a burr by grinding and a brush manufactured from the linear metallic brush bristle material.</p>
