In some areas, fluorite rich veins may be weathered to depths of as much as 75 m. Such weathered ore, a mixture of clay and fragments of fluorite and detached wall rock, may be mined open pit with draglines, scrapers, or power shovels to depths of as much as 50 m. Below that, underground mining methods, involving modified top slicing or overhead shrinkage stoping, are used.
Hengyang Mining:
Hengyang mining is commonly done by shrinkage stoping, cut-and-fill, and open stoping where strong walls occur. Closely spaced shrinkage stope bins may give way to widely spaced bins, with electric and air slushers being used in the tops of stopes to transport the overbreak to the ore pass. Air-operated, rubber-tired, muckhaul units can be adapted to in-stope work. Where shrinkage stoping is used, broken ore is commonly moved to the shaft by track haulage using battery-powered locomotives and 1- or 2-t side-dump cars.
With the introduction of diesel haul units of less than 1.5 m in width, mining can be changed from shrinkage stoping to ramp subleveling in veins. Loaders can be served by small diesel trucks carrying 3 to 4 t. Ventilation for the diesel equipment is usually handled by lines of woven plastic tubing. In shafts, bucket hoisting is supplanted by lifting in larger skips. In larger mines, crushers are installed over skip-loading pockets at the shaft bottom, which improves skip loading.
Room and Pillar:
In bedded deposits, room-and-pillar patterns are used, with the widths of rooms governed by roof conditions. Newer equipment has rubber tires and is diesel operated, including the muckhaul units—which have buckets ranging in size from 0.9- to 4.6-m3 capacity—and rubber-tired diesel trucks with 3- to 18-t capacity. Drilling is done by diesel-propelled jumbos in the bedded ore mines, but the jackleg drills are still used in narrower working places and drifts. In multileveled ore bodies, haulage ramps on 12% to 15% grades connect the levels. Vertical raises are used to facilitate ventilation requirements.
Most drilling uses tungsten carbide bits, or the throwaway- type hardened steel bits. In blasting, the trend is increasingly toward the use of ammonium nitrate–fuel oil mixtures. Mine crews, supervisors, and mechanics are usually provided with diesel personnel vehicles to facilitate mobility. Wherever widths of ore bodies, depths of overburden, economic stripping ratios, and the strength of the sidewalls permit, it is common practice to mine by open-pit methods, as is the case in Kenya and South Africa. This optimizes the obvious advantages to be gained by using lower-cost explosives, large-scale earth-moving equipment, and economical quarry bench mining methods.
Summary of Fluorite Ore Flotation Process
