Show ma mining na ng betl methods cods at park city 0 utah BY JAMES Hu HUMES ius the active mines of the park city district at the present time are the silver king coalition daly judge daly west and silver king consolidated several other companies such as the daly ontario american balg etc are doing considerable development work in the silver king coalition mines the ore is a replacement of a dark siliceous limestone bed varying in thickness from eighteen inches to several feet in places the ore has reached a thickness of feet this limestone bed lies within feet of the underlying weber quartzite there are other lime beds similar in appearance pe arance to this one in the park city for mation which is approximately feet thick but not one of them has been found to contain any traces of ore directly under and in contact with the ore bearing bed is another composed of grey lime well studded with dark nodules and this one is an unfailing indication of the proximity of the ore bearing bed the ore deposits make out from or have connection with some one of the ore bearing fissures which were undoubtedly the channels for the circulation of mineral bearing solutions it is therefore proper to run prospecting drifts in the fissures assures although they seldom contain much ore As a general rule drifting in the fissures is not costly mining and mucking cost from to 4 per foot and very little timber is required there are instances as in the daly fissure in the daly judge mine where the expense of keeping drifts open in the fissure is so SD great that it has proved economical to make the drifts in the rock crosscuts cross cuts into the fissure at short intervals in the park city mines it is not easy to determine beforehand the best method for extracting the ore from a newly dincov ered ore shoot in the bedded deposits while we may get one dimension from the drift run in the fissure that will not give us a correct idea as to the other dimensions of the ore body the fissures here referred to have a N 35 degree E strike and the beds dip from 10 degrees to 30 degrees NW the accompanying sketch map fig 1 is a tracing showing part of a worked out ore body and has a connection with an ore bearing fissure at the southeast end and feet highet higher up on the dip of the beds it will be noticed that the drift was advanced a long way in barren rock yet it was all the time in the Te replacement placement bed and where the ore is shown at the top of the incline it was very thin and discourage superintendent silver king coalition mines company park city paper presented at new york meeting of the A I 1 INT E reprinted from the bulletin of the A L I 1 M E r ing but persistent exploration developed a fine body of ore the ore bodies are somewhat in form with their greatest length along the strike of the lime beds the perimeter except on the fissure side is very irregular in outline there are numerous branches extending sometimes as much as feet and averaging from five to feet in widths width we also find the ore making up and down in small fissures for a few feet and we encounter rolls in ill the foot wall that make the beds almost vertical for from five to twenty five feet most frequently the ore dips down from the fissures that is the north dipping fissures and if our drift in the fissure has cut the ore we work down on it as far as we can by shoveling the ithe rock out if it persists in going down we rig up one of our many small hoists of which we have over a dozen ranging in size from a holman stretcher bar hoist to a double cylinder 35 hp these little hoists enable us to raise our regular mine cars if the angle is too steep for a direct pull we simply fasten avd 0 0 0 C 0 A p dr 18 s W A 10 1 mp OF WORKED OUT the end of the hoisting rope to a post at the top of the inclined and pass it through a 7 inch pulley which is hooked into the car this method gives the engine a double purchase and even with our little double cylinder 5 by 6 inch engines we are seldom unable to manage our 18 cubic feet cars if the deposit is too thin we take up enough of the bottom to admit the icar car very often our temporary inclines will meet with a face of barren rock in usch asch cases we do not cut through the waste but turn our rails to the right or left as the case may be and follow the ore see sketch map should the ore continue down on the dip for a cons considerable ider 1 distance we run small drifts right and left from our main incline in which we use a small special car dumping its contents into a hopper that connects with the car on the main incline should there be a sufficient thickness of ore at the point where we wish to run one of these sublevels sub levels we simply put down a track switch on the main incline the points of which we throw with a lever on the level that is connected with the points by means of a long rod crank and short rod and in this way we are able to load the mine cars that are hauled to the ore bins on the surface an experienced miner reading these lines will probably ask himself the question why dont they do their development work from the lower edge of their ore bodies As I 1 said before it is impossible to predetermine the outlines of such ore bodies when we took charge of this property we had many schemes for moving the ore from the faces to the levels the best and easiest of application was the shaking launder but as time went avent on we abandoned the thought of trying any of them at the present time we do as much underhand sloping as overhead sloping and in doing so we avoid doing a great deal of development work most of the time the deposit is so flat and thin that it is impossible to use a sloping machine to advantage so that most of our mining is done by the single jack method sometimes the ore gets down to a few inches thick but we do not abandon it until there is no sign of ore for many times a small stringer has led us to a large deposit the cost of mining ore here ranges from 1 to 4 per ton we believe that the above methods prevail in all the mines here where they are mining the replacement deposits following is a scale adopted ky by the daly judge mining company for running drifts and cross cuts with leyner machines the company furnishing all supplies av footage machine machine per shift men helpers muckers duckers less than 35 35 to 4 40 0 40 to 45 1 1350 45 to 50 50 to 60 60 to 70 |