Show lake superior copper conditions horace J stevens in a recent contribution to the mining and scientific press gave the following interesting account of the lake superior mines the old order changes and a critical observer well acquainted with the past history of lake superior copper mining can note the great change that is now being made in the production of the district with rare exceptions the old ml mines nes are marking time or going backwards while the younger and more vigorous properties are gaining ground that this should be so is not surprising for the richest mine has its bottom but 1 it t comes as something like a shock to the old residents accustomed for a generation or more to consider the great mines as immortal it should not be inferred however from the preceding statement that the old and large mines of the district are in danger of immediate extinction or that their managements have grown senile such fine old mines as the calumet hecla and quincy will last for another generation at least and discoveries of parallel cupriferous beds may prolong their life indefinitely in the case of the calumet hecla such prolongation lon gation due to the opening of new mines is reasonably well assured and the quincy has several copper bearing paralleling the great pewabic lode on which the mine is developed although it was originally opened and worked for some years in a small way and with indifferent results on the quincy old the improvement in methods and machinery has been marked during the past decade deade and every item of rock manipulation has been materially reduced for this reason it is possible to mine and mill much lower grade rock than ever before and some of the copper bearing and conglomerate beds pronounced worthless after exhaustive tests made many years ago will eventually be worked at a profit it is this possibility of developing parallel mines that gives hope for the remote future for the great old mines of the district the ore reserves of the calumet hecla are variously estimated at ten to thirty years the former figure is much too low as the mine has ground opened ahead of the sloping parties for nearly that length of time while the higher figure is based upon desires and hopes rather than on tangible measurements and estimates by virtue of lowered costs in mining and milling the calumet hecla can now work lower grade rock than ever before and the limit has not yet been reached in this regard the mine however has physical limitations and while its territory west of th tamarack undoubtedly carries the ft under lay of the calumet conglomerate roof the disappointingly low returns of copper given by all four of the deep vertical shafts sunk on the underlay of the conglomerate three by the tamarack and one by the calumet hecla renders it reasonably certain that at still greater depths the reef would prove still leaner hence there is lit it lle likelihood that the calumet hecla management will ever attempt to sink a two mile shaft to reach the conglomerate west of the tamarack the objections to such a shaft which has been given tentative consideration are many and serious As to time not less les than ten years would be required for sinking and a longer period might be needed the cost of sinking the shaft and equipping it with adequate hoisting machinery compressors pres sors and rock houses would be not less than and perhaps nearly twice as much the heat of the mine openings at a depth of two miles would preclude work except by the aid of artificial ventilation on a very extensive scale and it might be necessary to reinforce this by artificial refrigeration last but by no means least the conglomerate might be found pinched to unworkable dimensions or possibly cut out entirely though the latter contingency is a possibility rather than a probability and the copper contents of the rack rock would in all likelihood be very low the percentage of copper secured per ton of rock crushed is steadily decreasing at all of the old mines of the district this is true of the calumet hecla tamarack and quincy and the atlantic is the only old property df affording fording the proverbial exception needed to prove the rule the atlantic has always been of notoriously low grade and its best at the bottom of the mine show small change from those of the upper levels it is evident however in the case of the atlantic atlantic as of the other extensively ten developed mines of the district that the copper makes in courses or gigantic chutes that extend from surface to great depth usually running somewhat diagonally to the dip of the copper bearing bed fortunately for the lake copper district as a whole mining and milling practice are as advanced here heie as in any part of the world and the progress made enables the th e old mines to offset offee t decreasing richness of rock at depth with greatly increased tonnages ton nages and greatly lowered costs per ton in every department of production among the important changes of the past deca decade dehave have ben the adoption of much heavier hoisting plants high pressure boilers compounded engines 41 econ amizeri ami omi feed water heaters automatic stokers smokers sto kers automatic hydraulic ash dis chargers electric underground haulage improved crushers heavier stamps round mortars hydraulic classie firs and discharges coarse screens improved jigs and slime tables and the introduction of several highly efficient forms of patented concentrating cent rating tables for the saving of fine copper formerly lost in the smelters shelters sm elters the verber atory furnaces are several times as large 1 as ten years ago water tube boilers are heated by waste gases from the furnaces dipping and casting are done w with ith the aid of trolley lines and one man do does es as much work as two did ten years ago about a smelter all these improvements have united to greatly reduce cost and have saved the day for the old mines of the district d is but they have also set a new pace for the developing mines twenty five years ago the experienced men of the district said that half a million dollars was needed to properly open and equip a new mine ten years ago the figure had been raised to a million but the experience of I 1 the new mines developed in the district during the past eight years show that this sum was an underestimate at the present day an average of about is needed to properly develop and equip hn an important new mine allowing an average cost of for the lands and promotion in no other copper bearing district of the world is the cost of making a mine so great as here but there has b been een a proportionate onate increase in outlay required in all other districts the principal reason why lake mines are costliest cost liest to open and equip is found in the low grade of the rock which necessitates miles of openings to feed the big pill mill that is needed to allow the mine to secure a considerable production and earn profits the cost of opening the mines is usually less in other districts as the ore is richer and the country rock less refractory frac tory as a rule timbering is frequently costlier power plants are usually much less extensive and consequently far cheaper as the lake mines are the deepest in the world the concentrators of the copper ore mines are far cheaper than the stamp mills of the lake district the cost of a lake mill averages about per stamp and a modern 3 stamp or 4 stamp mill which is the size commonly built for new mines requires about eighteen months to build and costs a respectable fortune in the item of smelting smelling sm elting the lake mines have a great advantage over any other district as the raw charges fed to the furnace average CO 60 per cent to 80 per cent copper and the gangue is merely adhering trap conglomerate or old rock hence the only flux needed is a small charge of limestone the big smelters shelters sm elters and the intricate metallurgical processes common in many copper bearing fields are unknown in the lake Su superior perlor fields the sole disadvantage of the lake dito dis erict as a whole is the exceedingly low grade of its ore this is a serious matter and were the district not so firmly entrenched would prevent its development with far richer ores abundant at a score of points on the worlds surface the advantages of the district are low labor and fuel costs the best of rail and water transportation tati ample capital long experience and the best mining and milling equipment found in any field |