Identifier: placermininghand00coll (find matches)
Title: Placer mining. A hand-book for Klondike and other miners and prospectors..
Year: 1897 (1890s)
Authors: Colliery Engineer Company (Scranton, Pa.)
Subjects: Gold mines and mining Placer mining
Publisher: Scranton, Pa., The Colliery engineer co.
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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100 PLACER MINING. grating and are removed as often as necessary. Beneaththis grating stands the riffle box b, into which fine material,including gold, descends. The riffle boxes, of rough plank,are also placed on an incline, just enough so that the waterpassing over them will allow of the bottom becoming andremaining covered with a thin coating of fine mud. In thisway the gold and a few of the heavier materials find theirway to the bottom and rest there by aid of the riffle bars.Sometimes a little mercury is put behind the riffles to assistin retaining the gold, and the riffle box is supplemented bya series of blankets for catching very fine gold. Toms are
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Fig. 31. cleaned up periodically, and the gold and amalgam washedout with cradles. They are applicable only to workingswhere the gold is coarse, as they lose considerable of the finegold. Two to four men work at one Tom. Fig. 31 showsa Broad Tom in operation. PLACER MINING. 101 SLUICES. Sluices were introduced soon after the Tom. A sluiceconsists of an inclined channel, through which flows a streamof water, breaking up the earth which is thrown into it,carrying away the light barren matter, and leaving the goldand heavy minerals. There are box sluices and groundsluices, the former being raised above the surface, necessi-tating the lifting of the pay dirt into them ; the latter are sunkbelow the surface. Box sluices, or board sluicing, are longwooden troughs or series of troughs. They vary in lengthfrom fifty to several hundred feet, and are never less than 1foot, and seldom more than 5 feet, wide. The usual widthis 16 to 18 inches, and the height of the sides 8 inches to 2feet. The sl

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