Bisbee daily review., 1920-03-03
STARTLING ORE
 IS SUBJECT OF
 MINE LECTURE

A lecture on SampNlng was given last Wednesday to the class in prac- tical mining at the v. M. c. A. by Leon Feuchere. cnieT sampler for the Copper Queen mines. The speaker said in part:
 'In the mining of coppa~ ore in the Warren District. where o-ebodies are small and irregular, and where the grade of the ore throughout an ore body lacks uniformity, there are two more or less antagonistic nactors to be considered. The first is the cost of mining. and the second is the grade of the ore mined. In order to get a good cost. it is always a temp tation to mine as big an area as possible all together thus getting a larger tonnage per man shift. In doing this. however the grade Of the ore is liable to suffer. There, is al happy medium between the high cost required to obtain absolutely clean ore, and the cheap cost to obtai in a poorer, grade of ore. It is this happy medium for which one should str i've
 The Copper Queen figures out each month a grade of ore for ca ch stope, which will just pay expenses. This grade is called the minimum" for the stope. It depends upon and is figured out from four factors, tn @ market price of copper. the stope cost, certain proportion of the ottI CT mine expenses and the shelter cost which depends on the kind and amount of impurity in the ore, that is, the amount of fluxing material 1, such as iron, sulphur and lime, and | the amount of material requiring fluXing, such as silica and alumina.
 According to the needs of the smelter, we may have calls for spe- cial materials such as sulphur, lime, silica etc In such a case We have to mine ore which will fill such a de. mand. The sampling in this case must be very carefully done, the an- alysis must be run for copper as well as for the material sought and a new minimum must be established by the engineering department If the old minimum is used. reports for the place in question will not be accurate. It is very important that a new minimum be called for If special material is desired.
 "To obtain maximum profit from our orebodies close cooperation be- tween the mine and smelter is neces- sary. Where a great variety of ore
  careful estimates showing average grade and composition of the ore to be mined must be made. and the smelting practice must be designed to care for this average ore in the most economical way. On the other hand mining operations must be so conducted as to provide for uni form flow of average ore to the smelt- CT Occasions arise when it Is ad- yisable to depart from this proceed ure. Such occasions are brought about by various factors. Increase in the demand for copper and con- sequent rise in price may make it desirable to ship an additional ton mage of high grade ore.
 Any change in the composition of all ores received at the Douglas shelter may make it desirable to change the average composition Of the ores shipped from Bisbee. It is only by close cooperation that the maximum profit can be derived un- der these varying conditions.
 Correct sampling is one of the most difficult operations connected with mining, as a small sample is supposed to represent the grade of a relatively very great amount, and
 
 enormous error in the whole. To bring this point out the samples sent to the assay office are crushed up ,, and only a very small weight is used for the actual assay; the rest, called the reject. is sent back to the ore chutes. For the first six months of 1919 there was mined a total of l 241, ,696 tons oi ore. The assay office ! rejects in this period amounted to , 67S tons or only 0.29 of 1 per cent. For this reason it is necessary to check the samples several times in { order to get as reliable results as possible.
 "The route of the ore and where it { is sampled is as follows: First, it Is sampled before breaking in the stope. , This is done by the shift boss. or , rather it ought to be done by him, and it should be done very carefully because the future work of the stope | will be planned ou the return of the S samples. When the mine superin- tendent goes through the mine. his 4 orders may be greatly affected by 4 these samples. If a corner set is half good ore and half waste, you want to be sure that your sample in- ! Gicates that fact | After the stope sampling, the ore is sampled by the trammers as they I draw the chutes. each car being I sampled by means of sample shov- F el. The sample is put in powder boxes r carbide cans or in special sample T bins which are the best It is again sampled at the bottom of each haul r age chute by the motor crew. No k further sampling is done under ground The final Bisbee sample is \ that taken at the belts at Sacra- \ mento Shaft This is done by a \ special sample crew. shovel full be- \ ing taken for every 12 feet of belt : a bell ringing to indicate where to ' sample Twelve feet of belt repre- r sents approximately one ton of ore This belt sample gives the most ac- s curate results of all, and checks the z smalfar almost exactly IL oriunr thn .-