Change in mechanical condition by heat from dense to porous. Change in magnetic properties by heat. Change in surface properties by reagents due to adsorption or chemical reactions. Mine Development Stages We now turn to the procedures evolved by experience to cope with the these problems of complexity and heterogeneity in natural materials, and the implementation of the complex chemical and physical processes necessary to separate elements from ores. Stages in mine development will be described and illustrated by examples. The following four development stages apply in developing a mine, and following them conscientiously will be especially important with the additional unknowns of an extraterrestrial environment if financial - and other - disasters are to be avoided. Exploration This is the search for the highest recoverable concentration of the mineral or element available. For extraterrestrial resources, high grade is especially important because the extraction plant must be simple, cheap, and rugged to minimize capital and maintenance costs. It is highly unlikely that ordinary rock will be separated into all its components; indeed, this is impractical even in the much more favorable environment of Earth. Because of the high cost of element separation, it is always cost-effective to let nature carry out as much of it as possible. Laboratory testing Samples of the possible ore are tested by various techniques of physical separation and/or chemical separation to determine if the mineral or element can indeed be recovered. A high concentration of the mineral or element in the sample can only make the rock an ore if it can be recovered in a relatively pure form. This must be done on rock from the deposit under consideration; simulantswill not do. Only when the best site is found should a bulk sample be taken for a pilot plant test. Pilot Plant Test To estimate the mining cost, a large sample is dug from the mineral deposit to test the difficulty, excavation rate, equipment wear and power requirements. This sample is run through a pilot mill designed from the results of the laboratory testing. This step usually has to be repeated several times in order to balance the several steps and the equipment components so that they work together to give a clean uniform product. For large mines and plants, the pilot plant tests might be repeated in steps of about 100, 10,000 or 100,000 to 1,000,000 tonnes, depending on the
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