If you have access to OneMine as part of a member benefit, log in through your member association website for a seamless user experience.
|INTRODUCTION As man moved through the ages into the era of metals, he became increas¬ingly dependent on the extraction and beneficiation of various ore types. His progression has required more material, new sources, and inevitably, a need to extract the values from ores of much lower yield. Inherently welded to this need to extract has been the attendant requisite of power and water to carry out these tasks. With the richness of these deposits diminished, and the in¬crease of demand, mining has become so intimately tied with the needs of these auxiliary systems that the modern day milling operation can ill afford to ignore them. In the times of Agricola 16th century methods of milling required little thought for power or water consumption. Reduction was accomplished by hand¬sorting and hammer and grinding done with stamps and millstones. Medieval concentration was carried out by the "Jigging sieve" with agitation supplied by the sleeveless arm of the operator (The Mines Magazine,_ March 1933). Little consideration was likely given to the power source unless it became apparent that he had insufficient means to meet the demands of a dawn to dusk operation. Fuel for power production was also probably of little consequence unless sustained drought or warring neighbors burned the miners fields. Water was available from any adjacent stream with recycle, potable, tailings and mill consumption all going and coming from the same source. By the end of the 18th century and the early 19th century the requirements of larger throughputs and better re¬covery were forcing the miner to the need for greater sources of power and water. Arrastras, capable of accepting several hundred pounds of charge, con¬sisted of a clay bottom, a "liner of rocks harder than the substance to be crushed" and a revolving center post in which the ore was ground and amalga¬mated. Used in conjunction with a slucing system, this formed the primary recovery method of the time. Power was supplied by horse or oxen or, if terrain was amenable, by use of a horizontal or overshot water wheel. A typical system required 4.5 kw (6 hp) and needed to run in the vicinity of 15 rpm (Pre¬ston, 1895).|