ORE SAMPLING. Gold and silver ores are generally bought and sold by sample. In Colorado, where nearly all the silver lead ores, and much of the gold ore, is sold to public lead smelters for reduction, this custom is followed exclusively, and the methods of ore sampling have undoubtedly been carried to a higher degree of perfection there than any where else in this country. Attached to each smeltieg works is a sampling mill, in the samples are prepared. The usual arrangement of these sampling mills, and the method of sampling, are as follows : The ore, having, been unloaded from the wagons or railway cars, is taken to the mill, where the lumps are crushed to uniform size, say 1 in., by means of a Blake, Limn, Dodge, o• sonic other coarse-crushing machine. The broken ore falls to the floor below the crusher, whence; it is shoveled into barrows and wheeled away to i,ins in the roasting-furnace house or blast-furnace house, as the case may be. with the exception of every tenth shovelful, say, which is thrown to one side, forming a separate pile in the sampling milk With ores of average grade it is customary to throw aside every tenth shovelful, but with richer ores, every fifth, or even every third, shovelful is rejeet«I. The sample, constituting one-third. one fifth, or one-tenth of the original lot, is then wheeled to the sampling door, which is covered by a smooth iron plate, and quartering is emnintneed. A paragraph from a paper read by Dr. R. W. Raymond before the ,1 meriean Institute of Mining Engineers, June, 189 I, describes the method of quartering a sample as practiced at the leading sampling works of the West at the present time : " The mass is first shoveled into a ring on the sampling floor, and this ring is then shoveled toward the center, each shovelful being carefully delivered upon the summit of the pile in the center, so that they shall roll equally in all directions. A conical heap having thus been formed, it is pulled down and spread out. The workmen walk rowel and round, the pile, pulling with the shovel, as it were. the ore toward them, so that. it rolls outward. The lower six inches of the pile is not disturhed, and when this process is finished, the con heap has beemne a truncated cone of larger base area and 6 in. high. This tint. heap'
is now quartered by pressing a stick or a board ma edgewise, down into it so as to mark the diametrical divisions. 'i'wo opposite quarters are cut out with the shovel and removed. The other two arc again mixed, formed into a conical heap, and flattened out as before. This procedure is repeated until the quantity has been reduced to one or Iwo wheelbarrow loads. when, if the material has never been mechanically crushed, it is crushed in the rolls to, say. half-inch maximum size. 'I' he quartering is then continued till the sample has been reduced to a panful. This is ground, say, to 50-mesh size(after a partial preliminary drying, if nec essary, to facilitate the grinding in a rotary fine-crushe•), and then taken to the assay labora tory, where it is thoroughly dried (say, for• twenty-four boursal F.), and rubbed fine un til the whole will pass through an 80-mesh sieve. Quartering is then resumed and continued until the sample is only sufficient to fill three bottles, one of which is for the assay of the works, one for the customer, and the third for the umpire assay, if such should be required." In some sampling works automatic• samplers are used, in which case the original sample (say, one-fifth or one-tenth of a gross lot) is ertished by rolls to a convenient size, say SO as to pass a 4-mesh sieve, and the crushed ore is raised by a belt elevator to the top of the mill, where it goes through a iLenm screen, the ore which is rejected being returned to the rolls. The ore which has been crushed to proper size and passes the screen falls through a tui:e o• spout in which it is divided mechanically. The means employed for this all depend upon the same general principle of cutting or diverting the falling stream of ore by paeans of flanges, fingers, or traveling buckets, in such manner as to obtain any desired proportion of it for a sample. There are numerous automatic samplers in use, but most of them are constructed upon this principle.