Mercur, 1913
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Mercur, Salt Lake Mining Review, 1913
Very large parts of the text of a three-part article about the Consolidated Mercur mine and mill, from the Salt Lake Mining Review in 1913.
(Minor editing to improve readability, undo abbreviations, and remove detailed specifics of the actual milling process.)
Part 1
The Romance Of A Famous Gold Mine
By Don Maguire and L. O. Howard
Salt Lake Mining Review, June 15, 1913
Now that it would seem that the pall of death was about to settle upon the erstwhile famous camp of Mercur, Utah, where for twenty-two years the cyanide process has reduced millions of dollars in gold from a great mine that has furnished the queerest, most unassuming ore body in this world, it is interesting to go back to the incipiency of work in the old camp and learn as to how the discovery of the precious metals was first made at Mercur.
Well, it was in this way: Along about 1869 work began in Ophir canyon, which lies about three miles northward from where Mercur now stands. The ores at Ophir were silver-lead ores, chloride silver ores and silver-lead carbonate. Walker Brothers of Salt Lake City had built a mill at Ophir, and down at Stockton silver-lead mining had also made headway. There was considerable excitement as Bingham, Stockton, Ophir and the mines at Alta in Little Cottonwood were sending wonderful reports to the outside world of immense wealth opening at the grass roots; men were hurrying hither and thither into almost every mountain range in the then territory of Utah. From California, Nevada, Idaho, and the Sweetwater country over in Wyoming, miners and adventurers came flocking into Utah. The climate was ideal; supplies on which to live were cheap and abundant, the field an extensive one. Although tremendous discoveries seemed to have been made in White Pine county and at Pioche, Nevada, Utah, notwithstanding, drew a good part of the attention of that day. Gold was being taken from the placer mines in Bingham canyon and the silver lead ores accumulating at the mines in Alta, where the Emma and Flagstaff were making history, convinced mining men that Utah was destined to become one of the great mining fields of the American Union.
Such were the conditions, when, in the spring of 1870, men crossed over from Ophir into what became known as Lewiston canyon and discovered the outcrops of what was afterward known as the Sparrow Hawk silver vein. This vein lay almost horizontal in its outcrops and in thickness ran from six inches to over five feet in places. It was an antimonial silver ore or silver-bearing stibnite, the antimony going up to over 60 per cent and the silver values from 40 to 120 ounces per ton. At the time of the first prospecting being done in Lewiston canyon quite a number of the Utah settlers living down at what was old Camp Floyd rushed up into the hills northwest of their settlement, and within a few days a very large part of Lewiston canyon was located as mining ground.
Camp Floyd was then a pretty little settlement having about thirty families, most of whom were fairly well to do for those days. It was at Camp Floyd that Albert Sidney Johnston's army pitched its camp and constructed its quarters in 1858 and where it made its grand cantonment for more than two years. The waters from two big springs flowed, a large stream down into the valley to the southeastward. Prior to the coming of the army a few families of Mormon pioneers formed a settlement around the springs, opened up a few fields, and were quite prosperous when the army came. Upon the arrival of Johnston's troops, all of the citizen settlers were moved to the north side of the flowing stream and the army post was built on the south side. That army, known at the war department as the Army of Utah, numbered altogether, between officers, soldiers of the cavalry, artillery and infantry, teamsters, blacksmiths, carpenters and other tradesmen, almost 6,000 persons. They camped in that cedar and sage covered valley and under those mountains, so they little thought of possessing wealth of gold, silver, lead and copper amongst the richest mining fields of the world. In our day how little we may know of the things that are to come to pass.
Back in those early days of 1858 when that army came to Utah and camped in Cedar Valley, how little did the men who visited that camp realize the history that these men of that army were to make in the years to come. Walking that parade ground of the old Camp Floyd army post might be seen, as commander, Albert Sidney Johnston, who afterwards was the famous Confederate commander who was killed at the battle of Shiloh. With that army, also, was Commissioner Ben McCulloch, who, later, in the great rebellion, was killed at the battle of Pea Ridge; McIntosh, who was also a general in Price's army and who fell in the same battle of Pea Ridge, Arkansas, in 1862. With them also was Colonel McCooke, who made history in that great war. There was Captain Randolph B. Marcy, whose daughter became the wife of George B. McClellan. This man Marcy was he who made the famous winter march for 700 miles over ice and snow fields from Fort Scott in Utah to Fort Massachusetts in New Mexico, under the most frightful hardships, to obtain food supplies for the starving army at Camp Scott, near old Fort Bridger. In that army also was, as a boy, William Cody the great Buffalo Bill Cody, and also he who afterward became the notorious guerrilla chief known as Captain Quantrille of the Lawrence, Kansas, massacre infamy and who, at the close of his career, died like a dog in Kentucky. There also, as U. S. government guides and scouts, came the famous Kit Carson and Jim Bridger. With that command rode the famous Second Dragoons, who later on, while fighting for the Union, poured out their crimson life blood on many a field from Val Verde in New Mexico to Beverly Ford, in Virginia and with the veterans of that command were those who, around the soldiers fire in Cedar Valley, told of war time deeds and battle scenes they themselves had known, from the Everglades of Florida under General Jackson to the Valley of Mexico under Winfield Scott.
And now in Utah they little knew of what they were so soon to see of grim war in more distant fields, nor did these grizzled warriors realize the wealth that would be taken from the hills around them years after they themselves had laid down life's burden in the hospital, the trench, or on the bloody slope of the battlefield.
When that army marched away there were a few who, being discharged from service, remained at Camp Floyd. There was Snyder and McClain and McKinney from amongst the rank and file, and two clerks in the commissary, nephews of the great newspaperman Horace Greeley, their names, John and Mark Greeley. They remained in Utah when the army departed. Snyder, McClain and McKinney joined the church and married Mormon wives. The Greeley boys were handsome men; they lived at Camp Floyd for years, but did not marry. They were for a long time in the cattle business.
When in 1870 the men of Camp Floyd took part in the excitement of locating mineral land at Lewiston canyon, the Greeleys, the Carsons, the McKinneys, McClains, Snyders, Flocks, and the famous Bill Hickman were locators and when Captain Shaw and others came into the camp to buy and develop the Sparrow Hawk and other properties, almost all of the above locators made each a little money; about $70,000 all told came to the first locators in and around Lewiston. The district was named Camp Floyd Mining District. It was thought for a time that it was then to make one of the great gold and silver fields of Utah; the two known mineral lodes were the gold vein carrying much cinnabar or sulphide of mercury, a vein that was rich in gold, and the stibnite vein that was rich in silver. In 1872 Captain Shaw erected a mill in Lewiston canyon, or what was then the town of Lewiston, and efforts at prolific reduction were attempted on the two mineral lodes. A few silver bricks, by some means or other, were taken from the silver-bearing Sparrow Hawk vein and a bold attempt was made to amalgamate the gold values of the upper gold silicious vein, but the attempt was a failure. In vain were changes made in the mill; the results were no better. The assays of gold were good, but the known methods of treatment would not respond to the attempts of the millmen. With a heavy heart, Captain Shaw had to abandon the work, when he fully realized the mine was one carrying millions in gold, because no method known at that time would reduce the gold from those clay-like ores of that great vein.
As stated in the early part of this article, no mine had before known such a peculiar gold lode. The values were there, the laboratory tests of every assayer proved that, but the eye of man could detect no gold there and neither is the smelting furnace able to reduce these ores economically nor do the stamps in the amalgamating mill grind the ore fine enough to allow the quicksilver to act upon it, so with a heavy heart the man, who first made a grand attempt to reduce to profit the gold and silver ores at Lewiston canyon, turned away. The little camp was soon abandoned, the mill went to wreck, and offices and dwellings in the little town gradually fell a prey to the wholesale destroyer or the petty larceny thief; grass grew in the street of the silent little place, and in the warm summer days cattle would come and lie down to rest and peacefully chew the cud, where in bygone days Captain Shaw strove to create a roaring camp with his own and other people's money.
From time to time the wandering prospector would travel along the road that went through where the camp once stood, and from time to time these prospectors would examine the old workings and the outcropping mineral veins and wonder why was that their operation and development in the old days had been a failure. Finally there came along a German, who, seeing the bold outcrop of the gold vein and finding that it contained good gold values, resolved upon locating it, and having done so, he went still further, for he did the necessary work to obtain patent, which he secured from the government, and feeling that ultimately a method of recovery would be found to make the property of value, he went away into other parts and the stillness of death rested yet for many a day on old, desolate and almost forgotten Lewiston; one by one the years of the seventies stole away and in stole the years of the eighties and no change in the deserted camp. Its old history had become a mere memory until 1891 slipped upon the world. As we all know, about that time silver was receiving hard treatment from the men of this world and a call for more gold came from home and abroad.
In Utah, as elsewhere, the cry went up, "let us have gold mines worked; silver and lead are no longer in favor." Men came in from the Eastern states with money to buy gold properties, but would not look at a silver mine, if given it for forty cents. Then, as now, gold mines pure and simple were scarce in Utah. There was not being worked in all the vast territory of Utah a single gold mine, nor was there anywhere in the adjacent borders of Nevada, Wyoming or Idaho, a gold mine that would stand the test of assay sufficiently high to warrant equipment.
There were in Utah in the years 1891 and 1892 men who could make the average would-be investor in gold properties believe that Utah was the greatest gold field in the world, but investigation of the properties presented failed to give satisfactory results. About this time the fact that in the old days most excellent assay returns used to be obtained from the cinnabar gold-bearing flat vein in Lewiston canyon was recalled to the minds of several. Of course tradition told of the flat failure in attempting to work them profitably, but the fact that the vein there was of great thickness and that the gold values ran from $20 to $100 per ton was enough to suit the requirements of the man who wanted to bring his man of money into Utah.
The formation over there at Lewiston was strange and interesting. A tremendous metamorphosis had overtaken the original silurian limestone measures; great dykes had broken through the limestone; some of the limestone measures themselves had been converted into aplites, alaskites and other forms of soft porphyry. Where the apparently simple measures of the limestone were broken into, all the colors of the rainbow were exhibited in the bedding of the old limestone, and amongst these altered planes there was one that had received its enrichment of gold, making it the great Mercur vein on which men, as above stated, had lost time and money, and when, in the year 1891, men sought for bonanza gold veins in Utah, three men showed this property to the men from Nebraska. They had secured an option on the property from its German owner over in Nevada and added a simple two hundred per cent to the owner's price as a small commission in case of sale. At this point the irony of fate becomes evident in the fact that the three men who undertook the sale of the old Lewiston gold vein, now rebaptized as the Mercur lode, prepared themselves to be ready for instant departure from the confines of Utah upon the consummation of a cash sale of the famous gold-bearing Mercur lode, for did they not well know that all attempts at reduction of these ores had been absolute failures and would not history repeat itself with all subsequent investors. Alas, how little we know of what may come to pass. At that time the first visit to the shores of the United States from Australia was being made by the pioneer promoter, William Orr, of the now famous McArthur-Forrest cyanide process for reduction of low grade refractory gold ores. The days for the famous Mercur gold lode had about arrived, but not without sorrow and temporary tribulation, still, for those who were soon to become the successful owners of the Mercur gold mines.
Note: This is the first of a series of articles on the Mercur Mining District. The second article will appear in the next issue of The Mining Review. — Editor.
Part 2
The Romance Of A Famous Gold Mine
By Don Maguire and L. O. Howard
Salt Lake Mining Review, June 30, 1913
The story of the Mercur mine has been brought to the point where the promoters met the men from Nebraska, prosperous farmers, with money to invest. The promoters succeeded in their fondest desires and unloaded the property upon these men and arrangements were made to treat the ore by amalgamation — pan amalgamation — the Mercur Gold Mining & Milling company being organized for this purpose. A mill was built at Manning, some three miles away, where water was more plentiful than at Mercur. This company was formed in 1890. A ten-ton plant was erected at a cost of about $30,000, and the ore started through it. The ore kept on going through, mostly unchanged except that it was reduced in size, for the extraction was less than twenty per cent at a cost of $4 per ton. The operation, like its predecessors of the early days, failed of success.
An attempt was then made to treat the ore by roasting preliminary to amalgamating, and upon the assurance of one "Cyanide" Smith that he had $7,000 worth of amalgam ready, John Dern and E. H. Airis came on from Fremont, Nebraska, to be present at the retorting. With some ceremony the amalgam was retorted. The net result was a retort the size of a hen's egg. Dern and Airis threw up their hands. They were through, with the attempt to treat this rebellious ore.
All was gloom in the offices of the Mercur Gold Mining & Milling company. The owners of the worthless mine were in despair. Only two of the men connected with the enterprise refused to give up hope. These two, Gil S. Peyton, formerly a Tremont druggist, and Hal Brown, manager and stockholder respectively, having received a circular describing the MacArthur-Forrest process of gold treatment by the use of potassium cyanide, saw some of the possibilities for the Mercur ore, and against the arguments and opposition of officers and directors, samples were sent to the Metallic Extraction plant at Denver, on which recoveries of about 90 per cent of the gold value were made. By dint of much effort these men succeeded in getting out a car of ore. No money was forthcoming to pay the freight, so Peyton borrowed the money from the bank on his own responsibility, so sure was he of the success of the cyanide treatment. Eighty-five per cent, or thereabouts, of the gold was extracted, in the test on this lot made at Denver.
Peyton returned to Manning, where a tank was set up, the ore crushed and an attempt made to leach it. It would not leach; the solution would not percolate. Happening to notice some of the coarse rejects from sampling, he tried the effect of the solution on them and found that they would leach.
This showing convinced the owners to the extent that they rustled about and succeeded in mortgaging the mine to raise the money to remodel the plant. The original cyanide plant at Manning was but a testing plant as plants are rated nowadays. It had a Dodge crusher, Wall corrugated rolls, and five seven-ton leaching tanks. Eight men were employed in the mill and six in the mine, an interesting commentary on the labor thought necessary to carry out the process.
Although the tribulations were not yet over, the treatment had been started on the right track.
The Mercur Ores.
At this time only the oxidized ores of the camp were mined. These were of a reddish to brownish color, the values being in a silicious limestone, which was very porous and friable. Some of the ore was exceedingly talcy. The first thought was that the ore should be ground to a fine sand in order that the cyanide solution might reach the gold. This idea was fostered perhaps by the fact that the gold did not amalgamate, and even the microscope revealed no gold. However, the first attempts at extraction resulted in the production of an excessive amount of talcy slimes, which prevented percolation of the solutions. It was then that Peyton discovered that the coarse would leach.
Further study resulted in the application of the other pronounced property of the ore, its multiplicity of cleavages. The ore was full of small cleavages, on the planes of which the gold had deposited. It was found that in material as coarse as one inch, the solution would permeate these little fissures and pick up the gold. The idea so long spread broadcast by writers, that porosity of the ore enabled the solutions to act on the gold, is a wrong one, for the solutions did not penetrate the rock itself, but passed through the crevices, along the cleavage planes. There were two distinct advantages in this method, the absence of slimes allowing rapid percolation, and the coarse size of the particles making the crushing a simple problem.
The process then being in its infancy, but little was known as to what could be expected from it on Mercur ores. The first precipitates sent to the smeltery at Omaha were a source of mystery and were held in some contempt, and were carelessly handled for that reason. The smeltery did not know how to treat this "Mercur mud," but assays soon convinced them that a way must be found and it was found.
In the beginning the ore was given a wash lasting from four to six weeks. Strips of zinc were hung in the effluent solution in order to determine when solution was complete. The gold would discolor the zinc. Titration was not practiced. Solutions were standardized by rule of thumb.
Peyton and Brown left the company in about a year and sold their stock to the Dern interests. It is stated that Peyton received 25 per cent down, and that the dividends on his portion of the stock paid the deferred payments as they became due. So the change from poverty to affluence was rapid for this company.
The Railroad Enters.
The mill at Manning was gradually enlarged as the operators gained more experience with the process. It was first enlarged to a capacity of fifty tons, then, in 1893 to 100 tons. In January, 1895, the Salt Lake & Mercur railroad, tortuous but efficient, was completed from Mercur, through Manning, to Fairfield, a station on the Oregon Short Line, which at that time had a road down the east side of the Oquirrh mountains. This road, owned now by the Salt Lake Route, still handles limestone from the Topliff quarries to the valley smelteries, there being little passenger traffic on this section of the road. The coming of the railroad simplified the transportation of ore and supplies. Ore hauling by teams was suspended.
In 1896 the mill was treating 200 tons of ore daily. The flowsheet was as follows, - The ore was dumped from railroad cars to a bin, 49 feet by 20 feet by 20 feet, and was crushed in Dodge crushers and Wall rolls to about one-inch size. It was then trammed to 15-ton vats, 12 feet and 8 inches in diameter. These vats were of iron, with redwood bottoms and burlap filters. The treatment took about 40 hours, the ore being washed continuously with solutions containing 0.1 to 0.3 per cent KCN. The solution went to a collecting tank from which single acting Blake pumps delivered it to zinc boxes, where the gold was precipitated on zinc shavings. These boxes were 26 to 36 inches wide, 10 to 12 inches deep and 20 feet long. The cyanide consumption on ore containing $10 to $12 in gold was 0.6 pound per ton treated. The extraction was given as from 80 to 87 per cent, at a treatment cost of 85 cents.
In July of that year the mill was again enlarged to a crushing capacity of 500 tons and leaching capacity of 350 tons, the number of tanks being increased from 31 to 52. In 1897, as a result of increased capacity, the company was able to treat a lower grade ore, the values for that year running about $6.50 a ton. Mining cost $1,365; milling, 86 cents; transportation, 35 cents, a total of $2,575, leaving a net of $3 925.
The Latest Manning Practice.
In the latter part of 1898, near the end of operations at Manning on Mercur ore, the mill had one No. D Gates crusher and two 12-inch by 14-inch Wall rolls in the crushing department. After the first crushing the ore was elevated by a bucket elevator, 60 feet long, 18 inches wide, with buckets at 24-inch centers, to a 5-foot by 3 foot, 6-inch trommel, having apertures of one inch. The oversize went to the Wall rolls, and was returned by the same elevator to the trommel, thus completing a closed circuit. The undersize from the screen was carried by a 16-inch belt conveyor, running at an angle of 16 degrees, to a pulp bin in the tank room.
The tank room was 145 feet by 60 feet, and contained 10 tanks, 30 feet in diameter and 5 feet deep. Solution was run on through a 4-inch pipe, for 68 hours, the strength being kept at 1-1/2 pounds KCN to the ton. A 4-hour water wash followed. The pregnant solution was drawn off to a gold tank, of redwood, 12 feet, 8 inches in diameter by 3 feet, 6 inches deep.
For charging these tanks, two tracks were provided over each, and tailings were discharged by shoveling through four 11-1/4-inch gates to cars standing on similar tracks below. A horse was used to pull the cars to the dump, where they ran out on a self dumping section of the track.
From the gold tanks, solution flowed to a set of twelve zinc boxes, having compartments 12 inches deep, 30 inches wide and 12 inches long, thence to a sump tank, of the same size as the gold tank. The barren solution was then pumped to a storage tank, 12 feet, 6 inches in diameter and 6 feet, 10 inches deep. The solutions were standardized by what appears at first sight a crude method. At half-hour intervals, the millman added a predetermined amount of KCN to the head of each zinc box. When a single solution process was used, this gave excellent results. Not only was the solution easily standardized, but the increased strength of solution at this point aided the precipitation, and increases the recovery.
When cleaning up, the slimes from the zinc boxes were settled in a tank, 10 feet, 6 inches by 3 feet, 6 inches. The filter box used was 6 by 3 by 2 feet.
Screen analyses of the material treated show that about 72 per cent of it was coarser than 1/4 inch and about 50 per cent of the value was in these sizes. Likewise, about 45 per cent of the value left in the tailings was in these coarse sizes. At this time the extraction on the various sizes was between 69 and 78 per cent, and the lowest tails were the coarsest, running about 80 cents per ton, while the very small amount of the finest sizes ran up to $3.60 showing a very poor extraction on the slimed material. The general average was probably about $1.50, on $5 ore.
Quicksilver Recovered From Precipitates.
The consumption of KCN was 0.5 to 0.6 pounds per ton of ore treated, and of zinc, 0.3 pound per ton of ore. The precipitate was dried, boxed, sampled in Salt Lake and shipped to Argentine, Kansas. Its value was about $40 per pound. One of the most interesting features of the drying of precipitate was the recovery of quicksilver therefrom. The Mercur ore carried cinnabar, a small part of which was dissolved in the solutions and precipitated with the gold on the zinc. The precipitates were dried in closed iron retorts, and the recovery of quicksilver by volatilization and condensation amounted to nearly a ton annually. The peculiar features of the Mercur ore are manifest at every step.
The power house was equipped with one 60-horsepower and one 40-horsepower boiler, a 120-horsepower engine, a 120-light dynamo driven by a 11-horsepower engine, two zinc cutting lathes, and one pump.
For the year ending December 31, 1899 the average daily output was 353 at a cost of $1.05 per ton for mining, 68 cents for milling, 54 cents for miscellaneous items, a total of $2.27. Eight tanks, 35 feet in diameter and 5 feet deep, were added bringing the leaching capacity to 600 tons. The only alterations made in the crushing plant were to add another coarse breaker and to speed up the conveyors.
After 1900 this mill was run only intermittently by the company and lessees in the retreatment of tailings, for a new factor had entered the field originally occupied and developed by the Dern-Helmrich-Airis company, in the shape of Captain DeLaMar, who, in 1895, bought the Golden Gate group of mines adjoining the Mercur mine, and started development.
Developments at the Golden Gate.
In the development of the Golden Gate group considerable sulphide ore was encountered, which did not appear to be amenable to the cyanide process. The ore was a dark, often black, decomposed porphyry containing considerable pyrite, realgar and orpiment, compounds of iron, mercury, sulphur and arsenic, truly a discouraging combination to encounter at that early stage in the development of the process. Some investigators have given as the reason for the great refractoriness of the base ores, the presence of tellurium, but, it is pretty definitely established that no tellurium exists in the Mercur ore. Another reason advanced was that the gold was encased, in which event fine crushing would release it. The Consolidated Mercur company, however, has never produced any tailings containing less than 62 cents a ton, and fine crushing tests have resulted in no higher extractions, so that this reason proved untenable. Assays for carbon have shown that there was enough of this substance present to seriously interfere with the extraction, inasmuch as carbon is a precipitant for gold.
This ore proved a stumbling block for some time, but experiments conducted for a period of some two years showed that by crushing the ore finer, roasting and leaching the base with the crude oxidized, the base ores could be handled, so in 1897 and 1898, the Golden Gate mill was built. This mill, altered, improved and somewhat enlarged, was operated until early in the present year [1913]. In 1899, the DeLaMar's Mercur Mines company and the Mercur Gold Mining & Milling company — the Dern company — were combined and the Consolidated Mercur Mines company came into existence. All of the ore from the Mercur and Golden Gate mines was afterwards treated in the Golden Gate mill, the Manning mill being used only for desultory operations on tailings.
The Golden Gate Mill.
The original capacity of the Golden Gate mill was 500 tons. This gave it a position among the largest reduction works in the country. Power and light were supplied over high tension lines from a power plant in Provo canyon, forty miles away. At that time this was the longest single transmission line in the United States. Fuel for the dryers and roasters was provided by a Loomis gas producer plant. In these features, the plant was notable at its very inception. The gas producer plant did not prove a success and was practically never used.
In describing this plant the past tense will be used, although the description applies almost completely to the mill as it was operated early in the present year.
The mill was erected on a hillside above the town of Mercur, on a twenty-five degree slope, the difference in elevation between top and bottom levels being 160 feet in a horizontal distance of 380 feet. The width was 294 feet. The whole plant was built of structural steel and corrugated iron, with concrete foundations and retaining walls. These structures were not so common then as now, and this mill attracted attention among mill builders. An idea as to the slender but strong character of the construction can be gained from the illustration showing the leaching room.
The plant was erected on the Golden Gate mine, from which ore was hoisted in a three compartment shipway to the top of the coarse crushing building, which was 100 feet high. In two of the compartments 2-1/3-ton skips were hoisted by a double drum hoist, of Webster, Camp & Lane design, driven through a flexible coupling by a 150-horsepower Westinghouse 2-phase induction motor, running at 580 revolutions.
The dimensions and elevations of the various levels of the mill are shown in the accompanying drawing.
At the top of the crusher house the ore was dumped into one of three enormous steel bins, having a total capacity of 2,000 tons of ore, the arrangement of grizzlies being such that the ore could be distributed from either skip to any of the bins. Opposite the partitions of the bins, and on a lower level were the coarse crushers, two No. 6-D Gates, capable of crushing 100 tons per hour. These crushers were also driven by two Westinghouse induction motors. The crushers discharged into bins below, similar in construction to the receiving bins. These bins were about 20 feet wide, 25 feet high, and 75 feet long.
Drying the Ore.
In the drying room below the crushed ore bins were installed two Brown straight line dryers, 60 feet long and 12 feet wide, through which the arsenical and sulphide ores were run. Later two cylindrical driers, 8 feet in diameter and 30 feet long, with four radial compartments in each, were added, being placed in the center of the building between the straight line furnaces. The combined capacity of these driers was reckoned at 800 tons daily.
The conveying department occupied this same level. Robins belts were used to carry the oxidized ore to the fine crushing department beyond. Driers and conveyors were automatically fed by Gates roll feeders, and, of course, discharged automatically into the rolls.
Fine Crushing Department.
In the fine crushing section there were nine sets of Gates rolls, four 36-inch by 15-inch and five 26-lnch -by 15-inch; eight Berthellet screens inclined at 45 degrees (these were stationary screens fitted with rubber belting in such a way that the material being screened was kept on the jump, the undersize being caught in the chute beneath which discharged below the rolls); three large hexagonal revolving screens were soon added. Operations were so conducted in this department as to give a closed circuit, the final screened product being elevated in six 14-inch elevators to the storage bins, which had a capacity of 3,000 tons. Each class of ore, base, talcy or mixed, and oxide, was kept separate in this department so that each could be crushed to its own proper size, the oxidized being left much coarser than the base.
The base arsenical and sulphide ores were conveyed from the storage bins to roasting furnaces, of which there were four on two levels in the beginning, two being added within a year, making six in all.
The Roasting Furnaces.
The first furnaces installed, were the well known Brown straight line, with 12-foot by 100-foot hearths. One man attended two furnaces, each furnace handling about seventy-five tons of ore daily. The charge was rabbled once a minute. Six by eight flues carried the gases to the main dust chamber, into which the drier gases also discharged. Flues connected this dust chamber with an 85-foot stack on the hill. After roasting, the ore discharged to a wide bucket elevator which lifted the calcine to the upper cooling hearth, where it was moved back to the head end of the furnace, and discharged by spiral conveyors to pits below the furnaces, from which the ore was trammed in cars to the leaching tanks.
Soon after the installation of the four Brown furnaces, a Holthoff-Wethey and four modified Brown furnaces were installed. The Holthoff-Wethey roasted 145 tons of ore per day, with a fuel consumption of 8 tons of coal. The four Jackling furnaces, as the modified Browns were dubbed at this plant, roasted 70 tons per day each down to 0.1 to 0.15 per cent arsenic, with a fuel consumption of 7 tons per day. The average time taken for the ore to pass through the furnaces was eight hours. All the furnaces were soon changed to the Jackling modification.
The Leaching Department.
When the mill was built, ten 25-foot by 50-foot leaching tanks, five feet deep, were installed. There were three solution tanks 20 feet in diameter and 12 feet deep.
Early in 1899 the number of leaching tanks had been increased to twenty-two. Four tracks for charging cars ran overhead, and four below, with eight feet clearance, for handling tailings. The ore was spread by shovelers. Fifty tons of oxidized ore was first spread on to a depth of ten inches, then base ore added. Three men filled a tank in eight hours. A 0.4 per cent KCN solution was then admitted through two 10-inch openings in the bottom, for eight hours. This solution stood for ten hours, then more solution was fed on top and drawn off through the same openings to gold storage tanks of 150 tons capacity. On the up current a 14-foot head was maintained. After 24 hours of strong solution on the top, a 0.3 per cent solution was run on for 48 to 72 hours, then a two to three days water wash. Percolation was at the rate of one inch per hour, using two tons of solution to each ton of ore.
Precipitation Department.
The precipitation department contained three steel precipitating tanks, 14 feet, in diameter and 8 feet deep, with a capacity of 40 tons each. Precipitation was accomplished by means of zinc dust, this plant being one of the early examples of the use of zinc dust. Details will be left for future consideration.
The solution and precipitated gold was run to ten Smith-Vaile plate and frame presses, which produced a product containing 60 per cent gold. The zinc consumption was about 0.4 pounds per ton of ore, when treating $7-ore.
Two cycloidal pumps, of 1,200 gallons per minute combined capacity, returned the barren solution to storage tanks, of which there were three, above the leaching section and north of the roasting department.
Power.
Electricity for power was brought in at 40,000 volts, 3-phase, and transformed to 220-volt, 2-phase. Details of power plan and power distribution of this early mill differ but little from the latest practice used in 1913, and their description will be included in a later article.
The assay office and refinery occupied a 30 by 80-foot building near the end the roasting department. This building was destroyed by fire, but the new structure is shown in the same location in one of the illustrations to accompany the next installment.
The description of the Golden Gate mill, as originally built and operated has been given in some detail, in order to show properly what features it possessed as one of the greatest plants in the country in the early days. It will be found also that few changes have been made in the construction, and enlargements were brought about largely by increasing the number of units.
During the early life of the plant the personnel was as follows: Victor M. Clement general manager; Duncan MacVichie, general superintendent; D. C. Jackling, assistant superintendent.
This plant, with the mines, was taken over by the Consolidated Mercur Mines company, and operated by them after August 1st, 1900.
The first report of the new company contains interesting information as to what was accomplished at the plant up to the time of consolidation. From April 1st, 1898 to August 1st, 1900, the DeLaMar mines milled 449,694 tons of ore, from which $2,236,737.28 in bullion was produced at an operating cost of $1,546,924.29, leaving a net profit for the period of $689,812.99. This makes an average recovery of $4.97 per ton of ore treated, at a cost of $3.44.
The Mercur Gold Mining company had milled, up to August 1st, 1900, 595,422 tons of oxidized ores and paid $1,490,500 in dividends. The net profits of the two companies were $1.53 and $2.50 per ton respectively.
So that up to the time when these properties consolidated they had produced 1,045,136 tons of ore at a profit of $2,190,901.79.
Who of the pioneers would ever have ventured to suggest that such would be the output of the formerly despised holes in the ground? What would have the essentially dishonest promoters thought could they have foreseen that the base metal of their ambitions was to be transmuted into the gold of success, by the poor farmers whom they so assiduously swindled? Yet the romance but begins to unfold.
Note. This is the second of a series of articles on the Mercur Mining District. The third article will appear in the next issue of The Mining Review. — Editor.
Part 3
The Romance Of A Famous Gold Mine
By Don Maguire and L. O. Howard
Salt Lake Mining Review, July 15, 1913
Let us see in what kind of a position the Consolidated Mercur Mines company was when it took over the constituent properties. What were its possessions? What were its prospects?
In February, 1901 the properties of the Consolidated Mercur included 944 acres of mining ground, a 1000-ton cyanide plant (the Golden Gate), a 600-ton cyanide plant (Manning), hoisting works, machine shop, steam and electric compressor plant, electric tramway, water system, offices, dwellings and all necessary buildings.
R. C. Gemmell, now general manager of the Utah Copper company, estimated the ore in sight January 1st, 1901, as 1,117,320 tons having an average assay of $6.08. In his report to the company he estimated that mining and milling would cost $3 a ton and the tailings loss would be $1.
A glance at the table containing the summary of operating results shows that the estimate of cost and tailings loss has been borne out remarkably, that the estimated tonnage has been exceeded, but that the grade of ore has not been maintained, due to several reasons, one of the principal being that lower grade ore could be treated at a profit, and it was difficult to avoid mixing poor ore with the good. In order to keep up its tonnage it has also been necessary for the company to treat a lower grade ore. In fact, the main disappointment that the company has had to contend with has been the constantly diminishing grade of ore. It has been found impossible again and again to maintain for one year the grade of ore which was estimated the preceding year.
For the first three years of its existence the record of the new company continued to be romantic, in that it was exceedingly good. For the three years ending June 30, 1903, the company treated nearly a million tons of ore, from which over four and a quarter million dollars in bullion was obtained. Dividends of over a million dollars were paid, and the mill was run at a capacity of about 900 tons a day, with the best extraction that the company ever succeeded in getting. The losses in tailings were high, but to counteract this, expenses were gradually cut.
Up to February, 1901, in addition to the base ore, which was roasted, and the oxidized ore, which was treated raw, a third class, known as mixed, was maintained. This ore contained a little arsenic and sulphur, having some characteristics of the base ore and was very talcy. The finely crushed mixed ore was calcined before treatment. In February of that year, Superintendent Janney, who has since become prominent as superintendent of the Utah Copper company's great mills at Garfield, was in charge, and made attempts to treat the oxidized and mixed ore together making but one class of them. By making a cleaner separation between the base ore and the new mixed, it was found that it was unnecessary to roast this portion of the ore. The mixed ore was charged to a depth of two and one-half feet and roasted base ore distributed on top. A satisfactory leach was obtained, a part of the roasting costs were eliminated, and much of the fine crushing avoided.
Early in 1902 the driers were done away with, thus cutting out another item of expense. At this time, one-third of the ore, all base, came from the Golden Gate mine. The base ore of the Mercur mine, although coming from the same strata, carried less sulphur and arsenic and was much easier to roast.
The Moore Slime Process Tried.
For the six months ending May 1, 1903, the tailings averaged $1.30 a ton. In the attempt to overcome this loss, experiments were made with the newly invented slime process, evolved by George Moore at the Sunshine mine in the same district. It had not met with success on the Sunshine ores, but Mr. Moore assured the directors of the company that he had now worked out a practical process. The mechanical features were examined and approved by a mechanical engineer, and with high hopes construction was begun in May, 1903. The tests led to the conclusion that 50-cent tailings could be obtained. It was estimated that the plant could be installed in three months.
Eight of the twenty-six leaching tanks, which the company then had, were given over to the slime plant. Trouble and grief were continuous. Defect after defect appeared and was remedied, until in June 1904, over a year later, nearly $60,000 had been expended on construction, the company being compelled to spend money in perfecting details, which Moore should have perfected himself. A little more experimentation by Moore would have saved the company thousands of dollars. But Moore had jumped from a small laboratory filter, to leaves that were twenty by four feet. They were unwieldy; the vacuum pump was mounted on the basket; there was no classifier available to separate all of the sand from the slime and consequently the material packed in the vats; the flat bottom tanks did not permit using any efficient agitation; stresses set up in the huge plates cracked the cake; the vacuum failed and dropped the cake, and in fact the equipment was worthless because of faulty mechanical construction. Yet inventors are prone to do this very thing today. It would seem that most apparently meritorious inventions which fail are handicapped by mechanical faults.
The net result of the years operations was a loss of four cents a ton. The plant was thrown out on May 26th and no further attention has been given to the process at Mercur. Had the Moore process succeeded there would undoubtedly have been some profit from operations. But pioneers must suffer in the early days of untried processes.
Trials and Tribulations.
The fiscal year ending in June, 1904, was full of trouble. The tailings averaged monthly as follows: 83 cents, 84 cents, $1.08, 89 cents, 95 cents, 94 cents, 94 cents, $1.02, $1.24 and $1.43. The low grade of the base ore caused the company to put four of its roasting furnaces out of commission, five being retained. From July to December, 750 tons were treated daily. From January to May the tonnage was below 500. During June and thereafter an attempt was made to maintain the tonnage at 600.
In the following year, although for short intervals tailings losses were heavy, the average loss was reduced and milling costs took a big drop.
In 1906 an additional set of rolls was put in commission in the crushing department and the sixth furnace was again brought into use, and an average of 68 tons per furnace was roasted. In the leaching department, tests showed the advisability of using lime instead of caustic soda for neutralizing. Lime proved to be cheaper and the cyanide consumption dropped. Attempts were made at treating slime by decantation methods, but settling difficulties with the talcy ore, and lack of water limited its application.
Lack of storage capacity at the mill coupled with mine troubles caused many interruptions to smooth operations in the year ending in June, 1907. Other causes contributed to a bad year; coal shortage, power troubles, repairs to shaft, etc., were disastrous to mill results. An attempt was made to leach the oxidized ore alone, but slime troubles prevented satisfactory leaching.
Slimes Plant Installed.
An experimental plant had been built in July, 1906 and experiments were made as to the limit of crushing, solubility of values, strength of solution, ratio of solution to ore, time of treatment, desirability of agitation, settling efficiencies, decanting and filtering. Results submitted to the directors were met with an authorization for a 400-ton slime plant, which began operations in July, 1907, on a small scale, and was completed in September. Results were so good that no ore was treated except in this plant. Tonnage was too low (500), however, so the slime plant was given all it could handle and the remainder of the ore was treated in the old way. The slime plant did not work well on base ores. Very low tailings, 44 to 48 cents a ton, were obtained while treating straight oxidized ore, but when base ore was added to the charge, the losses rose to 90 cents. However, in the months when the slime plant was down the tailings ran over one dollar a ton so that the value of the slime plant became apparent, even for treating base and oxide ores combined. It was deemed more economical, nevertheless, to put the slime plant on fine oxidized ore, and to leach the base and coarse oxidized as before.
In 1908 experiments looking to the adoption of zinc shavings in place of zinc dust for precipitation purposes, led to the decision to retain zinc dust.
On May 8, 1908, the collapse of part of the leaching plant put eight tanks out of commission, so that since then but eighteen tanks have been available for leaching. More tanks and filter frames were then added to the slime plant to make good the loss in capacity.
The scheme of treatment from this time on was to dry screen the oxidized ore into two classes, fine and coarse, the latter making an ideal leaching product. The fine oxidized and the roasted base were then sent to the classifiers, slime going to a filter plant and the sand to the leaching tanks.
Progress has been briefly traced from year to year.
Last Mercur Practice.
The last skip of ore was hoisted on Sunday, March 30, 1913. The practice to be described is that obtaining for the few months preceding that date. The method of hoisting and distributing the ore to the bins is the same as described earlier in these articles. The grizzlies used are ten and sixteen feet long, the bars having a top width of one inch and a bottom width of seven-eighths inch. They are set on a 45 degree slope. Two No. 6 Gates crushers do the coarse breaking. Dimensions of equipment will not be repeated at this time where no change has been made since the erection of the mill.
[Pages 11-15 describe specifics of costs and milling processes, and do not apply to the history of the mine and mill.]
Water.
Water for milling at Mercur is obtained from the Gold Belt Water company, in which the Consolidated Mercur company has a one-half interest, control and management. The company has a water power pumping plant in Ophir canyon, five miles from Mercur, which lifts the water 1,300 feet to the top of the divide between Ophir and Lewiston canyons, from which point it is distributed by gravity. The power plant has one and one-half miles of 18-inch and 15-inch pipes, and ten miles of main distributing pipes.
The Consolidated Mercur company also owns a farm on Ophir creek carrying a water right for twenty acres.
Costs.
[Costs for 1912 and 1913 were about the same.] The tonnage averaged 400 per day.
Among those connected with the Consolidated Mercur company as directors were John Dern, John Heimrich, E. H. Airis, H. A. Cohen, W. H. Cunningham, George H. Bennet, Isaac H. Meserve, Edward T. McLoughlin, William M. Thompson, G. H. Dern, A. N. Chesterson, Henry A. Bingham, W. S. McCornick, Hubbard W. Reed, J. E. Frick and George E. Airis.
On the operating end of the DeLaMar mines, the Mercur Gold Mines company and the Consolidated Mercur are such names as D. C. Jackling, now of Utah Copper, Walter T. Janney, now superintendent of Utah Copper mills, Duncan MacVichie, a prominent Salt Lake mining engineer, George Z. Edwards, George Dern, the late William Orr, who represented the MacArthur-Forrest process in this country and had charge of the Manning mill for a time, Ernest Gayford, now of the General Engineering company, of Salt Lake, Gil S. Peyton and Hal Brown, who were responsible for the original cyanide installation. At the close of the company's operations C. W. Poole was general superintendent and N. N. Bley, metallurgist. From these two much of the information as to the latest practice was obtained, and our thanks are due them. We wish to thank also A. Reeves, secretary of the company, for a complete file of the company's reports.
The Romance Ends.
With the paying of an additional dividend in June, of $30,000, and the dismantling of the plant now under way, the romance of this great property ends, although there may be a sequel coming, in the shape of further small dividends, accruing from the sale of the equipment.
It is doubtful if any other successful company can show a record of so many difficulties overcome, so many disappointments endured and surmounted. Had the company been able to start operations a few years later, when the cyanide process was further advanced, the profits would have been larger, but the romance would have been missing. The romance has had its price as is evident from the rehearsal of troubles met.
The last year or two the company has just managed to live, from hand to mouth. One of the greatest difficulties, to which we have given little attention, has been the condition of the mine. The opening up and development was well planned and executed. As much cannot be said of mining operations. In the beginning an attempt was made to mine a bed of ore in places eighty feet thick by using stulls for timbering. As a result only one-third of the ore was mined in many stopes before caves came to bring down the rest of the ore. The mining methods since used have been called caving systems. The caving method, if such it can be called, was not intentional. The ground caved because of early faulty mining, after which it became a question of mining caved and running ground. In some of the old stopes which had caved, in recovering the remaining two-thirds of the ore, men have shoveled for months in one spot, taking out the ore as it ran down to them. Driving through this kind of ground and keeping the excavation open has meant a very high mining cost. This in connection with the mixture of ore and waste, and the otherwise low grade ore has finally resulted in suspension of operations.
From beginning to end the properties comprised in the present holdings of the Consolidated Mercur, have paid, including the last payment made in June, the impressive total of $3,445,312.97 on a bullion production of over $17,000,000. No one can fairly ask for more romance.
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