Kaolin Mining Definition Kaolin is one of several types of clay, and is commonly referred to as China Clay or Paper Clay. It is a hydrated silica of alumina with a composition of approximately 46% SiO2; 40% Al2O3, and 14% H2O. It occurs in hexigonal plates, often in worm-like bunches. Geologically, kaolin comes from decomposition of feldspar in soft, disintegrating granite, gneiss, and porphyritic rocks—granite rich in soda-feldspar yielding it in greatest abundance. History The term kaolin is derived from the Chinese word "Kau-ling", meaning high ridge, having reference to the locality from which the richest supplies were obtained. In Georgia, kaolin was first mined in Colonial days and shipped to England. The famous Wedgwood Pottery there used considerable amounts of clay from the colonies until the English mines were opened. This ended the mining in Georgia for over a century. In 1876, mining here was resumed, and at present continues as the major mineral production of the state. Indeed, Georgia produces about 72% of the total kaolin production of the United States. Uses It is of interest to note that of the some one and one-half million tons of kaolin produced annually in the United States, approximately 56% is used in the paper industry. In paper-making, kaolin is utilized as a pulp filler as well as for coating. Filling adds weight, opaqueness, and whiteness; coating gives high gloss. Some newspapers have a kaolin content of about 2%, while magazines with a relatively high gloss contain on the average of 30%. With the advent of high-speed coating equipment, the production of paper clays increased to the extent that it has nearly doubled in the past ten years. Rubber products consume about 16% of the kaolin, with a major portion of the remainder going into such products as linoleum, paints, inks, leather, refractories, and pottery. Within the past few years, kaolin has been used in insecticide, fertilizers, and plastics. No doubt other uses will be found for the mineral. Mining Operations The mining methods in the recovery of this mineral are practically the same as any strip operation. The overburden is removed in advance of the mining operations. Overburden varies in depth up to 100 feet. The clay seam has an average thickness of from 12-15 feet, although in some localities it is as much as 30 feet thick. Mining methods have advanced as earth-moving equipment developed. At one time, the conventional method of overburden removal was by locomotive and dump cars, hauling from power shovel to dump area. This method required a large crew to clear the tracks as well as shift and realign them. Several operations use this system in bringing the clay from the mine to the mill for wet processing. Perhaps the first development from this stage was the belt conveyor and stacker to replace the train haul with its subsequent unloading crew. Such a unit was installed at several operations with considerable success. A series of 36" belt conveyors 500 feet long feeding a stacker were placed parallel to the overburden wall and mounted on sets of track at right angles to the conveyor. This long conveyor was fed by feeders loaded with power shovels. The feeders were also truck mounted, and moved along the conveyor as the face of the overburden was advanced by the shovel. The stacking conveyor was about 100 feet long and set at a vertical angle of about 20 degrees. This unit was mounted on caterpillar treads to move parallel to a section of conveyor termed the dump conveyor. The dump conveyor, some 300 feet long was provided with a tripper to feed the material on to the stacker at any particular location along the dump conveyor. A bulldozer was used to level the stacks as the dumping progressed. As shorter hauls and less overburden were encountered, this unit was replaced by the tractor-pan operation. As haulage became longer and the overburden increased, rubber mounted equipment came into use. The latest equipment of this type is the Euclid Earthmover. This unit is a twin-engine, six-wheel scraper, which is capable of loading itself from the solid bank in overburden as well as in clay. It has an average struck capacity of 18 cubic yards and heaped capacity of 24 cubic yards. It moves with a full load at 30-35 miles per hour. It is equipped with torque converters and hydraulic drive so that either motor can be operated individually, or both motors simultaneously. These units load, dump, and level the piles while moving, so there is no idle time during round trips. The only down time is for greasing, refueling, and maintenance. Transporting Some plants using wet methods of refining have developed a unique method of moving the clay from the mine to the mill. Clay is brought from the pit to a mill at the mine by truck, train, conveyor, or other earth moving equipment, where it is blunged and then sent to the plant by pipeline. Blunging is a ceramic term meaning "mixed with water." Most of the pipelines average about four miles, but one is 11 miles long. For normal flows, the 11 mile line requires only one pump, but a booster pump is in the line for higher flow rates. One operation in the mining of clay that is unusual is the machine that mines the clay and mills it in one unit. This unit is connected by pipe line with the plant, and makes a very compact operation. Milling and Shipping The kaolin slurry when sent to the plant is subject to various processes depending on demand. The processes are many and varied and will not be dealt with at this time. The refined product is usually shipped in the dried form in bulk, bags, or in sealed hopper bottom cars. With certain processing to keep the kaolin in suspension, it can also be shipped in liquid form by tank car. About 86% of the kaolin exported goes to Canada, with smaller tonnages going to Mexico, South America, Europe, and Asia. The Mines Magazine March 1952