The Alaska daily empire., 1915-01-09
UNUSUAL STARTLING
 AT EBA AfR MINE

The development. work at the Ebner
 mine which has been going on now
 for more than 8 year under the super
 lntendency of D. D Muir Jr, hes tafn' ishea considerable experience m iefGe samphuE aecording to the report OF meeting of the New York section
 Of the Mining and Metallurgieai so'
 ciety of Amerlca appearing in the Engineering and Mining World or Der cember 26 Sidney j. Jennings ad' dressing the meeting described some unusual expedients found necessary
 by the U. g. Smelling. Rehndins &
 Mining Exploration Co. In its work on the Ebner property which 1t has
 under option. His description iol'
 lows
 "Thez ore was supposed to carry 92 in gold. from which 9 profit Of 70 cents per lon was expected. An err. TOT of 20 cents per ton in sempling might cut SS l-S per cent from our profits The question wos, were -we
 taking specimens or samples! We were cu-ting chelnels six inches wide by two to three Inches deep five feet apart In the crosscuts; and while one might suppose h0t P there were en- ough crosscuts thp law of averages would hold and errors would balance themselves. we found that succe85iYe 5.foot samples would assay from a trace to SIP or even higher per ton; hence. lt seemed unwise to depend on averages. when the total number of samples would necessarily be small
 ''We therefore took samples over a strip 1-2 feet wide along the cross cuts for the full height getting 90. ton samples for each 12-foot crosscut. These We ran through fve-stamp mill At first SO-mesh screens were used, but finally slotted screen equivalent to 6O-mesh. The plup from the stamp was run into 8 12-iuch launder and the stream was cut at periodic intervals, taking out , 3a per cent ae a sample. This sample was amalgamated. and the tailings from the amslgamoting barrel were sampled. which could loo done with accuracy to within four cents per ton.
 "Yet we were never satisfied that the gold recovered in the amalgamot ing barrel was the right proportion of that lD the original ore. Suppose you took 82 samples of three-Quarters pound each from tue same ore crush ed to 40-mcsh. If you crushed each sample to 100 mesh and split It. the halves would vary by say four cents 8Ut il you took another or the orl- ginal S2 samples. the variance be- tween it and the first might be rom S150 upward showing that even with 40-mesh material individual pieces of gold would so through the Quartering process and not be propordonately distributed. Our minman inally put In a Wiifey table Co concentrate the 30 tons. We concentrated out aoouJ 4-z per cent or lhe Qtlblnai. which carried all tho free gold Che pyrite, galena, etc The tallngs from this table could be sampled accurate ly. The concentrates were amalga- mated in a barrel, the tailings from which could also Joe sampled. In order to ascertain the value of the original sample of thirty tons VIC had the fol. lowing factors: Net dry weight of ore crushed; weight of concentrates total amount of gold re- covered in the amalgamating barrel; assay of the tailings from the barrel; l assay of Che tailings from the Wiley table; total amount Of gold remaining in the sand around the dies in the battery This plan has been working three to four months and we really i have secured results that cheek"