. The sampling and estimation of ore in a mine . .—Enormous body of very low-grade copperore, occurring in form of small grains of chalco-cite; could be determined easily by the eye that the softparts of the ore were leaner than the hard; adits weredriven into the ore-body, and samples were taken every 5ft., alternating from side to side, so that samples were 10ft. apart on each side; a separate mill-test was made onthe ore from each adit; thus it was possible to comparethe average of the mine samples with the average value ofthe ore as milled. Varying results were obtained in thedifferent adi
. The sampling and estimation of ore in a mine . .—Enormous body of very low-grade copperore, occurring in form of small grains of chalco-cite; could be determined easily by the eye that the softparts of the ore were leaner than the hard; adits weredriven into the ore-body, and samples were taken every 5ft., alternating from side to side, so that samples were 10ft. apart on each side; a separate mill-test was made onthe ore from each adit; thus it was possible to comparethe average of the mine samples with the average value ofthe ore as milled. Varying results were obtained in thedifferent adits; in those where bunches of soft ore werescattered promiscuously throughout the harder ore, it wasfound necessary to add as much as 15 per cent to the aver-age values shown by the mine samples, to make themcorrespond with the mill-tests. Case III.—The property was represented as being alarge body of low-grade, free-milling gold ore, having awidth of 500 to 600 ft. The only workings were two open- ^/c///? of C?c//cro/s>, ^00:^0 £001^:^. cuts and two shallow shafts. The deposit had a width ofoutcrop of 500to 600 ft., but a careful examination showedthat its actual thickness, while great, was only 50 to 60 —189— SAMPLING AND ESTIMATION OF ORE IN A MINE ft. The accompanying sketch shows how the mistake inestimating the width occurred. The ore-deposit was inquartzite, containing here and there small, irregular seamsof quartz. It was observed that the quartzite itself car-ried values, although values were higher in the quartzveinlets. The gold was finely divided, and only rarelyvisible to tJie naked eye. In bucking the samples, for thepuq^ose of quartering down, once in a while a few piecesof rock would be found showing comparatively coarsegold, and such pieces were rejected as a matter of ore was sample<l in lo-ft. sections across the deposit,269 samples being taken. These samples were buckedand quartered down by hand in the usual manner, exceptthat, befo
Size: 2178px × 1147px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, bookcentury1900, bookdecade1900, booksubjectores, bookyear1907
