The rule is designed to protect miners, working on and around surface highwall drills, from exposure to harmful amounts of dust containing crystalline silica. Quartz is a natural constituent of the earth's crust and is not chemically combined with any other substance.
Silicosis is a disease of the lungs due to breathing of dust containing silica particles.
Silica dust can cause fibrous or scar tissue formations in the lungs which reduce the lung's ability to work to extract oxygen from the air. There is no cure for this disease, thus, prevention is the only answer. There are several stages of silicosis. Early stages may go completely unnoticed. Continued exposure may result in the exposed person noticing a shortness of breath upon exercising, possible fever and occasionally bluish skin at the ear lobes or lips.