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From the 1924 book, A Popular History of American Invention. Original chapter title, “Mining Copper and the Nobler Metals.”
WHAT metal did Man first find and use? It may have been silver or copper; some say iron, others lead, tin, zinc, even steel or brass, which latter are not natural metals. Most probably, gold was the earliest discovered metal.
A miner knows that ancient man was most likely to have used gold first, because, more than any other metal, it is found pure in nature. The archeologist finds gold ornaments in ancient man’s graves, with stone weapons and tools.
Gold was bright and attractive. Ancient man learned to trim and hammer it into ornaments, and later to melt it. In the same way, it is thought, he soon found silver: but that, too, was used chiefly for ornament.
Man’s first working metal was copper. Combining it with tin and melting them together to make bronze, he had a metal with which he built great kingdoms and cities, and through long centuries he fought bloody wars without ever using iron. The wonderful civilizations of Mexico and Peru knew only these three or four metals, and many of their weapons and tools were of stone.
The Greeks and the people of Crete and other Mediterranean islands began to use copper about 3000 B. C. It was not known in western or northern Europe until nearly one thousand years later, when Phoenician traders brought marvellous copper ornaments and weapons to the stone-age people.
The Phoenicians got tin from Cornwall, in England, and mixed it with copper to make bronze, which they found harder and better for their purpose. The Greeks began to use iron in the thirteenth century B. C., but bronze was still popular. Five hundred years after the appearance of iron amongst them, the Greek poet Aeschylus spoke of it as “the stranger from across the sea.” It became common in Greece about 1000 B. C., after a bronze age lasting two thousand years.
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|(Left) PRIMITIVE METHOD OF TRANSPORTING ORE. (Right) EARLY METHOD OF TRANSPORTING ORE BY A WHEELBARROW, ACCORDING TO AGRICOLA, 1550. From drawings in the Deutsches Museum, Munich.|
To-day, we have about fifty metals, some of which are seldom used. Most of us probably have a dozen different metals in our pockets, contained in articles such as money, knives, watches, keys, fountain pens, and so forth. In fact we carry gold, silver, copper, tin, iron, zinc, nickel, lead, aluminum, with a bit of rarer metal like iridium here and there, on the nibs of fountain pens, or in things made of alloy steels. In a bicycle, motor-cycle or automobile, a dozen more of these rarer metals may be found.
Except in the case of iron, mining is a needle-in-the-haystack affair. The haystack is a mountain, and the needle a very small quantity of metal. Sometimes this metal is a vein of gold, silver, or copper, deep in the mountain. Again it may be a very small quantity of metal scattered in streaks through the whole mountain.
The miner’s job is to find the vein and get the metal out, or tear the mountain down and grind it up to get the metal.
Scientists have worked out a theory of the origin of metals; the process which they now believe was followed by nature. They know that most of the rocks on our globe, especially the very hard ones like granite, were once molten and liquid. As they cooled, cracks would form in the granite of a mountain.
Water, escaping from the hardening rock, would rise through these cracks in the form of vapors, which carried atoms of metals. These metals would be deposited along the cracks, and thus ore veins would be created in the mountain.
Nature no sooner raises a mountain than she begins tearing it down. The rains fall upon it and sweep into its crevices and cracks, forming underground streams. These streams may run along a vein which has a very small deposit of metal, but they will wash it loose and carry it down to some deeper crack, and there collect it in a much more valuable form which, some day, miners will find.
Wind, ice, heat, the roots of plants, even animals, help in this work of tearing down the mountain. Its rock is reduced to sand, and this is washed away into streams and rivers miles distant. Metal is also dislodged and carried along by streams, sometimes in particles finer than sand, sometimes in large lumps. The metal sinks into the river beds, and it is in such places that man first found gold and silver in fair-sized lumps.
Copper is not so easily found. Sometimes it can be picked up in lumps of “native” copper, but usually it is mixed with rock. Scientists reason that early Man, probably an Egyptian, banked his camp fire with pieces of copper ore in some place like the Sinai peninsula, at the head of the Red Sea, where copper existed, and the next morning discovered glittering hard drops of the metal that had been melted out.
“Without knowing, this man stood at the dawn of a new era, the Age of Metal,” says Professor James Henry Breasted in his book ‘Ancient Times,’ from which some of these facts about man’s earliest uses of metal have been taken.
“The little bead of shining copper which he drew from the ashes, if this Egyptian could have seen it, might have reflected to him a vision of steel buildings, Brooklyn bridges, huge factories roaring with the noises of thousands of machines of metal, and vast stretches of steel roads along which thunder hosts of rushing locomotives.
Since the discovery of fire over 50,000 years earlier, man had made no conquest of the things of the earth which could compare with this discovery of metal.”
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|TRANSPORTING ORE ON A SLED. ACCORDING TO AGRICOLA, 1550. From a drawing in the Deutsches Museum, Munich.|
These drops were first used for beads until people learned that enough of this new metal could be melted out of rocks to make knives, spear-heads, arrow-heads, axes and working tools.
Copper weapons were so much better than those made out of stone that men armed with them soon gained mastery over their less inventive enemies, just as centuries later, men who invented iron and steel weapons vanquished enemies who had only weapons of bronze. With copper, too, men had better chances in hunting and fighting wild beasts.
Mining really began when people needed more metal than they could pick up from the ground. For hundreds of years a family might go through life with only a few ounces of copper: a knife, an axe, a spear, a chisel. But when armies needed weapons, the need for this metal became more urgent.
Man could not wait for nature to wash the needle out of the haystack. He had to go to the mountain, find the vein, and dig the metal out.
HOW THE PROSPECTOR DISCOVERS THE ORE
The first step in mining to-day is prospecting. When ancient man decided to go and find the metal in the mountain, he was no longer satisfied to sit down in a river bed and look for nuggets of gold, or silver, or lumps of copper ore, but walked up the river, keeping his eyes open, tracing metal to the deposits from which it had come. Every mine, great or small, whether it yields gold, or copper, or zinc, or diamonds, was first found by a prospector in the same way.
The prospector is the most romantic fellow in the mining business. He leads a rugged outdoor life, tramps hundreds of miles into the wilderness, lives partly by hunting and fishing, carries the fewest tools and supplies, and sleeps in a tent or under the stars.
To be a successful prospector, he must know a great deal about technical matters, such as geology, ores, metals, and even natural history. He sees things that would not be noticed by other people, puts two and two together, and makes deductions as subtle as a detective; a Sherlock Holmes, pitting his wits against nature to find the wealth she has hidden in the mountain.
The fascination of the work is so great that many men remain prospectors all their lives, by choice, though settling down and working a mine would usually be much more profitable. It is the independence and change and freedom from routine work, the exciting chance of making a wonderful discovery to-morrow that keeps prospectors roaming the hills, seeking mineral wealth that the engineer and miner may later develop into rich mineral industries.
With his donkey, or “mountain canary,” following along behind with supplies and tools, the prospector walks up a valley, watching for “float,” the name given to pieces of rock containing metal. These “floats” may be found either in a stream, washed down by water, or on the valley floor, having dropped from the mountains above. He may go for days before anything promising turns up.
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The prospector of antiquity looked for just a few metals: gold, silver, copper, tin, lead. To-day he may find riches, not in gold, but in some metal like tungsten, for which the world had little use twenty-five years ago.
In a certain Western silver mine which had proved rich about fifty years ago, when the silver was taken out the miners were bothered by some queer black stuff which they hauled to the surface, sorted out, and threw on the waste heap. It was tungsten, now used to make filaments for electric lamps. It has since been gathered up and sold for more than the silver in that mine was worth.
A time comes when the prospector finds ore-bearing rock, not one or two pieces, but a trail of it leading up the mountain. It may take him days to clear away bushes and plants, working from one spot to another. He may have to clamber back and forth on steep slopes, examining every place from which rock has fallen off.
Finally, if he is lucky, he discovers the place from which this “float” has dropped, and it is an exciting moment when he chops and digs to see if there is more than one outcropping of mineral, and whether it looks like a big vein running into the mountain, and how much metal there is in the ore.
But not once in a hundred such times does he discover a rich mine. His vein may hold a real fortune in metal, but the mining engineer must decide whether it can be taken out at a profit.
The vein may be a hundred miles from a railroad, and the cost of removing the ore may be in excess of its actual value. Some day the railroad will come there, and the ore can be sent to the mills and smelters.
Ore must be crushed to powder and run through separating machinery, and for that a steady supply of water is needed. A discovered vein may be miles from water, in the desert. Separating machinery requires steam or other power, and it would not be profitable to haul coal so far.
Men will be needed to work the mine, and they may be scarce in that region.
There are many other things to be reckoned with besides simply finding a good vein of ore. One “strike” in a hundred may be worth working as a mine, and even then, perhaps only one in a hundred mines prove profitable. Indeed, there are so many chances against success in mining, and so many failures, that experts have said the world puts more money into gold mines than it ever takes out—meaning that though some gold mines pay, the money sunk in those that fail is greater than the value of the gold.
This is rather a gloomy way of looking at mining, but it has a basis of truth. Much of the silver now mined in this country, being mixed with zinc, or lead, or other bulkier metals, can be mined only as a by-product. That is, the cost of getting out the silver alone might be more than it is worth, but the other metals pay expenses.
There are many such combination mines in our West, where the lead or zinc brings good prices one year, and the next lead or zinc may be too cheap to mine, the silver paying expenses.
Occasionally, the prospector finds a small deposit of ore so rich that he can take it out himself and haul it to a mill. Some gold miners search for rich “pockets,” and wash the metal out of the gravel or earth by hand.
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Mark Twain was once a “pocket miner.” He and his partners one day discovered what seemed to be a promising pocket. Mark Twain was carrying water to wash the gravel, which was getting richer and richer. The day was cold, and being chilled, the great humorist refused to carry any more. “Just one more bucket !” pleaded the man who was washing. But the water-carrier struck work then and there, and something took them away from that place. Two other miners came along later, found a rich pocket, and took out $20,000.
It is of gold and the days of “forty-nine,” when a famous discovery lead us to the great wealth of metals locked up in our country, that most Americans think when they hear the magic word “mining.”
In colonial times there was little mining, because, apart from iron and coal, and some zinc in New Jersey, our Atlantic seaboard is poor in metals. Some gold had been found in the Southern States, and it is a little-known fact that one of the first stamp mills in California for breaking gold ore, was set up by a gold miner from Georgia, and still produces small amounts of this metal.
We now produce twenty per cent of the world’s gold, forty per cent of its silver and lead, fifty per cent of its zinc, and sixty per cent of its copper and aluminum.
Except the last metal, which is not mined, but reduced from clay, these metals are mined West of the thirteen original States. Copper is found in Michigan, and lead and zinc in Missouri. But the far Western States produce the bulk of all our nobler metals.
It was the discovery of gold in California that opened up these treasures, and set our inventors at work developing wonderful mining machinery, for it is the natural resources of the country that stimulate inventors. Other countries have perhaps outstripped us in gold production, but through our inventions we lead in metals like copper.
It is not generally known that the value of the copper we mine every year is greater than that of our iron.
“THE DAYS OF OLD, THE DAYS OF GOLD, THE DAYS OF FORTY-NINE”
On January 24, 1848, nine days before California was added to our territory under the treaty with Mexico, a carpenter, named James Marshall, was repairing a mill-race on a branch of the American River in the valley of the Sacramento River, in California. It had been dug to carry water for a saw-mill, but was not deep enough.
The night before he had turned a great volume of water into it and had allowed it to run all night. That eventful morning he saw some bits of bright yellow stuff in the gravel that was left behind. Picking up one of these yellow fragments, he hammered it and found it was a soft metal. He then put it into a boiling kettle, only to discover that it did not dissolve, but came out as bright as ever.
Thinking it might be gold, he took it to his employer, an enterprising Swiss, named John A. Sutter, who owned several thousand acres of land in that neighborhood, with many thousands of horses, cattle, and sheep. Several hundred men worked for him, and they had a fort for protection against the Indians.
Sutter had some nitric acid among his chemicals, an acid that will tarnish nearly all the metals, with the exception of gold. Marshall’s bright yellow stuff remained untarnished. Then Sutter weighed it, compared it with a gold coin, and declared it was gold.
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The news spread. Not only did Sutter’s ranch hands leave him to become gold-seekers, but they also ran away with his horses. The Indians refused to harvest his crops. He was beggared, and neither Sutter nor Marshall ever profited by their discovery, both dying poor, some years later.
Two years afterward, in 1851, more than $80,000,000 worth of gold was mined in California. Men flocked in from everywhere. They left places like San Francisco, then little more than a village, rushing to the region where gold had been found. Sailors deserted ships, the neighboring Mormons came from Utah, people from the Eastern States crossed the prairies and mountains to reach California, and also went in ships by way of Panama, where they rode across the isthmus, taking another ship on the Pacific side.
The rush was so great that a railroad was built across the isthmus to connect profitable steamship lines, opening in 1855. Other gold-seekers came from South America, and even from Australia, where gold was found in 1851 by Edward Hargreaves, an Australian who had been in California and learned where to look for the rare metal, and how to detect it.
With such a rush of adventurous men into a wild country, that to all intents and purposes possessed no government, there was some lawlessness, of course. It is a mistake, however, to think that all “forty-niners” were desperadoes, though this belief has come down as a sort of tradition. The greater number were young, healthy, vigorous, intelligent and enterprising men; only a few were outcasts, gamblers, and criminals.
Though rough in dress and language, they were yet sober and trustworthy, and were not only law-abiding but able to establish government, make laws, and keep order. Had they been otherwise, they would never have founded a great new State, nor the vigorous industry that mining has since become, with its wonderful machinery for handling millions of tons of ore. Keeping the world supplied with metals, even gold, by the hand methods of 1849, would be no better than going back to prairie schooners to haul freight across our vast continent.
The first gold-seekers in California had only such tools as they could carry with them as they roamed from place to place looking for gold near the surface. First, they had pick, shovel, and “pan”; the latter a wide, shallow dish of metal like a flattened bread bowl. A shovelful of gold-bearing dirt was put into this, and the miner rocked it in his hands, working out over the edge, first the larger stones, then smaller and smaller ones, until a little sand was left at the bottom, from which he skilfully separated the gold.
An early California miner, named Buffam, who washed gold in 1848, the year of the Californian discovery, has written about it:
“I shall never forget the delight with which I first struck and worked out a crevice. It was the second day after our installation in our little log hut—the first having been employed in what is called ‘prospecting,’ or searching for the most favorable place at which to commence operations. I had slung pick, shovel, and bar upon my shoulder, and trudged merrily away to a ravine about a mile from our house. Pick, shovel, and bar did their duty, and I soon had a large rock in view.
“Getting down into the excavation I had made, and seating myself upon the rock, I commenced a careful search for a crevice, and at last found one extending longitudinally along the rock. It appeared to be filled with a hard, bluish clay and gravel, which I took out with my knife; and there at the bottom, strewn along the whole length of this rock, was bright, yellow gold in little pieces about the size and shape of a grain of barley.
“Eureka! Oh, how my heart beat! I sat still and looked at it some minutes before I touched it, greedily drinking in the pleasure of gazing upon gold that was in my very grasp, and feeling a sort of independent bravado in allowing it to remain there.
“When my eyes were sufficiently feasted, I scooped it out with the point of my knife and an iron spoon, and, placing it in my pan, ran home with it much delighted. I weighed it and found that my first day’s labor in the mines had made me thirty-one dollars richer than I was in the morning.”
But not all gravel is as rich as that, and very often the gold in a river bed has worked down to bed rock, making it necessary to dig to some depth.
For washing the poorer gravel, a “cradle” or “rocker,” a box mounted on rockers, with a perforated sheet-iron bottom, was used. This held several shovelsful of dirt, and when water was poured on it and the mixture rocked, the finer particles of dirt, with the gold, fell through the bottom upon a canvas screen. Then it ran over “riffles,” or transverse bars of wood, holding mercury, and the gold formed an alloy with the mercury and was saved.
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|CRADLE AND UTENSILS FOR GOLD-WASHING USED BETWEEN 1849 AND 1856 AND PRESERVED IN SOUTH KENSINGTON MUSEUM, LONDON. The cradle is a rough wooden box on rockers; in the head is a sieve into which is shovelled “pay dirt,” while water is poured over it by the tin dipper, and the cradle is rocked by a handle. The gold, sand, and fine particles carried by the water through the sieve are guided by an inclined frame below the latter to the head of the box, and flow down the sloping bottom. A blanket stretched over the frame retains very fine particles, while coarse gold is caught by transverse ledges or “riffles” on the bottom. The pebbles left in the sieve are picked over by hand, in case a nugget be present, before being thrown aside.|
Another variation of this method was the “Long Tom,” a wooden trough into which ran a stream of water. Into it the miners shovelling earth and “rifles,” with quicksilver, caught the gold at the other end. But among people as inventive as Americans, these crude tools were sure to be improved.
Gold-seekers stopped roving and settled down in camps; for as time went on gold was not so easily won. What little there was on the surface had been found; prospectors now had to dig down to bed rock or tunnel into a hill for it. From the first, this work was very hard. Forced to stand up to their waists in water, as they washed gold in a pan, or compelled to pry and lift up stones so that pay dirt could be shovelled into a rocker, these men were sure to find better methods.
In the past, gold-bearing dirt found far from water had to be carried to streams for washing. Then miners began to carry water to such places in sluices—wooden troughs often miles in length, bringing water from the mountains.
This led to hydraulic mining. Water coming from the mountains was used with great force to wash down whole hills, being spouted through nozzles in powerful streams, the gold caught with quicksilver.
There was one rich hill of gravel into which hundreds of miners had dug holes, the dirt from which they had hauled some distance and washed in a stream. When water was brought to that section in a sluice, the whole hill was soon washed down by the hydraulic method.
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Hydraulic mining in California was begun in 1852 by a Frenchman named Chabot. He had a gold-bearing gravel bank near a stream on higher ground, and brought the water down in a hose, where he intended to wash the gravel after shovelling it into a sluice. His hose was four or five inches in diameter, and about forty feet long.
After a while, instead of shovelling the dirt, he turned the water directly upon it and swept it into the sluice. It was the first use of a powerful stream to wash dirt instead of shovelling it.
In 1853, another California miner, E. E. Matteson, rigged up a hose with a metal nozzle and directed the stream against a gravel bank. By this method he found he could do as much work as a hundred men. Out of his nozzle was developed the “monitor,” a tapering nozzle that concentrated the water and increased its force. With the monitor, and a good supply of water, large streams of terrific force could he thrown hundreds of feet.
In a short time hydraulic mining came into general use wherever there were gravel banks to which water could be brought in sufficient force. In a single season, whole acres of ground would be undermined as much as 200 feet below the surface, washed away and run through sluice boxes, leaving their gold.
These monitors moved dirt so fast and cheaply that they were later used to cut through gravel hills in railroad building.
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|HYDRAULIC ELEVATOR USED IN DRIFT MINING, NOME, ALASKA. The sand and gravel are pumped up with water and the ore separated by the riffle method. Courtesy United States Bureau of Mines.|
THE QUARTZ MINER ATTACKS THE MOUNTAINS
But already gold was being found imbedded in quartz—one such discovery had been made in 1850—and thereby a wonderful new field was to be opened up to the American inventor. Quartz mining is so different from the simple “placer” mining of early California days that placer miners did not always know wealth when they saw it in quartz.
In 1849, a party of Mormons bound for California stopped to pan gold in a little creek in Nevada. Disappointed, they passed on. Yet that little creek was the door to one of the treasure vaults of the world, for the Comstock lode, on the border of Nevada and California, was an ore-body 125 miles long.
Mexicans came two years later and, washing gold up the creek, found the great vein from which most of the gold came, but did nothing with it. In 1856, two brothers named Grosh found that a metal there, about which gold miners complained, thinking it was lead, was really silver, but they died before they could take advantage of their discovery.
Finally, in June, 1859, two miners, Patrick McLaughlin and Peter O’Riley, washing gold in that region, found it in astonishing abundance on some un-worked ground.
Just then a trapper, Henry Comstock, happened along, saw the gold, and insisted that they were trespassing on his ranch of 160 acres. It was pure bluff, but he argued with them until they gave him an equal share in their discovery, and thus the name of a keen-witted rover was given to that ore-body which men had been on the verge of discovering for ten years.
These miners knew nothing about quartz mining. Indeed, the mining of silver in this country was unknown before the Comstock lode was found. They sold their claim for a few thousand dollars, and all died poor, Comstock a suicide.
That brought the inventor, the engineer, and the financier to the aid of the miner. Up to that time the latter had been little more than a wandering prospector, taking only such loose gold as he could find, and separating it from dirt and gravel with the simplest tools.
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The prospector of to-day seeks veins of metal rich enough for quartz mining. Carrying his samples of ore back to civilization, he has them “assayed,” or analyzed, to find out whether they contain enough metal to be worth mining. If they do, and he can interest men of money, a trained mining engineer is sent to the place from which the samples were taken, where he studies the vein, estimates its probable size, location, and richness, and whether the ore can be mined and its metal taken out at a profit.
He brings pack animals carrying many tools the prospector has probably never heard about, instruments to survey the ground, and with him go helpers to dig and tunnel in different spots for the vein. A surprisingly correct estimate can often be made, because mineral veins generally have certain ways of running, and the mining engineer has learned much about them from study and experience.
His helpers go to work upon the outcroppings with drills and dynamite, and if their findings show it to be a mine really worth working, then the property is sold to a mining company, or more often a new company is formed to work that particular mine.
More machinery is brought in. Air-drills to bore holes rapidly, with air-compressors and engines to furnish power; hoists for cars to get the ore out of the mine; machinery to crush it, and separate the metal from the worthless rock dust.
Very soon a village grows up around the spot where a few months before the lone prospector had chipped and dug in solitude. Miners hurry to the scene with their families. In that out-of-the-way place they will find a store where they can buy their various wants, often a school for their children, and perhaps a moving-picture show for entertainment. The mail-carrier soon makes his appearance.
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Soon there springs up a stage line from the nearest railroad station, or nowadays an automobile stage running on a road built for hauling out ore with motor trucks. If it is a great mine, requiring years of work to extract all its metals, the railroad will come, and the mining village will grow into a permanent town.
Many years of work may be ahead of miners, as is shown by the deepest mine in the world, the No. 3 shaft of the Tamarack copper mine in Houghton County, Michigan, which has reached a depth of 5,200 feet, or practically one mile.
Such very deep mines are warm, for the deeper men go the warmer it gets. Rock temperatures of 158 Fahrenheit have been faced by miners with good ventilating apparatus, without which they would have to stop from sheer exhaustion, even though great wealth lay beneath them.
It may be that, instead of a rich vein and single mine, the prospector and engineer have discovered a great new ore-body like the Comstock lode; or the gold deposits at Cripple Creek, Colorado, and Coolgardie, Australia, which two mines were discovered and opened up on opposite sides of the world at almost the same time, about 1890.
Then there is excitement! Prospectors, miners, and adventurers join in a “rush,” ranging over the new district, exploring, finding new outcrops and veins, staking out claims, and sometimes fighting over disputed discoveries, or getting possession of rich claims by theft and murder. That was more common thirty or forty years ago when, in districts like Cripple Creek, prospectors suddenly found gold in very hard rock, left by an extinct volcano.
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The West was then a new country, and lacking means of preserving order in out-of-the-way places. But times have changed since then. In one of the newer mining regions developed in recent years in a flat desert country, instead of the red-shirted gold-seeker of old days, prospecting is often done by men who work in the mines week-days, and run out into the country roundabout with an old automobile on Sundays and holidays.
In April, 1919, two prospectors in a worn-out “flivver” were bumping over a California road. They were John Kelly and Ramp Williams, the latter a half-breed Piute Indian. Kelly’s hat blew off. Williams got out and found it in a small hole which some prospector had dug years before. Picking up some loose rock, he said: “This looks like silver ore to me,” and he filled Kelly’s hat with the stuff.
“That’s the best hat I’ve got,” objected Kelly. “I wish you would use something else for an ore-sample bag—but we’ll have it assayed.” Thus was discovered California’s largest silver mine, the California-Rand, at Randsburg. In its first year it yielded more than $1,000,000 worth of silver.
WHAT ONE SEES IN A MODERN METAL MINE
Visiting a modern metal mine, and noting its complicated machinery below and above ground, one finds it similar to a modern factory. Many inventors have helped to bring this mining system to a state bordering on perfection, although there is yet room for the more ingenious inventor. But neither machinery nor engineering science have destroyed the thrill of mining.
As the veins of metal-bearing rock are followed into the mountain, they may grow thicker and richer, or else may taper off and become poor. They may widen out again, or they may stop dead.
In many cases where they do stop dead, mining engineers make surveys of the direction in which the veins have been running, and figure that so many hundred feet further on, through solid rock, they may be found again. So they start new tunnels to reach them by the shortest distance.
Sometimes the calculations are correct within a few feet, sometimes it is work for nothing. On the other hand they may run into an entirely new vein. In this and other ways men still find thrills a-plenty in mining, and there will be thrills as long as we are willing to pit our technical knowledge and fortitude against the secrets held by Mother Earth.
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|MINING IN THE SIXTEENTH CENTURY ACCORDING TO AGRICOLA AND LOHNEYSS. .A. Smelting-furnace. B. Windmill for ventilation. C. Drawing out the air by bellows. D. Horse-windlass for raising ore. E. Incline. F. Water-wheel driven by a stream and serving to pump up water in several stages. G. Local fire for heating and thus loosening the ore. H. Windlass for raising the ore. J. Bottom ore bed. Courtesy of Deutsche: Museum, Munich.|
Let us investigate what engineers call the “non-ferrous” mining industry, the mining of metals other than iron, that is, gold, silver, zinc, copper, lead, tin, and the like. Iron mines are described in the chapter written by L. W. Spring, and the great coal-mining industry in the chapter by Floyd L. Darrow.
To start with we must put on “digging clothes”—hobnail boots and khaki—because we are going to walk maybe miles through dark tunnels, climb ladders, pick our way through great boulder-floored caverns, and ride up and down from one level to another in “cages” or “skips,” as the mine elevators for raising ore are called.
Once we would have carried candles or lanterns, but to-day the mine superintendent gives each of us a dazzling little acetylene lamp, or an electric torch. We follow him into the mine. It is dark in a moment, and we are lost in the mazes burrowed through the mountain.
Great timbers support the enormous weight above our heads. As miners tunnel through, the rock and earth above must be supported by timbers, for which reason the lumberman finds the miner one of his best customers. In time, deserted tunnels cave in, and are thus closed by nature.
When all the ore has been taken from a particular tunnel, the miners fill it with the rock blasted out in tunnelling or getting ore, from immediate parts of the mine, and this saves hauling such unprofitable material to the surface.
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We dodge cars of ore hauled by mules or electricity, follow pipes carrying the compressed air for the drills, and presently come to a place where the miners are drilling into the ore itself. There are great piles of broken ore behind them, waiting to be carried out. Climbing over this broken ore, we come right up to the “face” of the vein itself. It may be like ordinary rock, or it may glisten and shine.
“Just look at that ore !” exclaims the superintendent, “Go right up to it—why, that’s good enough to eat !”
But for all we know they might be building a subway or driving a railroad tunnel, and it is difficult to see where the vein ends and the rock begins. Metal mining is just subway and tunnel-building, with a little difference. When the subway or tunnel is bored, the work is practically done; but in mining it is never done until all the ore has been taken out. If all the miles of mine-tunnelling could be used for subways, there would be enough constructed every year to give subways to most of our cities.
It was for driving railroad tunnels that inventors devised much of the machinery used in metal mining to-day. If you are driving a tunnel through a mountain to carry railroad passengers for many years, the quicker you can get the job done and begin earning money, the better; in this case, cost is less important than speed, and for that reason expensive new machinery was first tried on railroad tunnels. But if you are driving a tunnel into a mountain merely to take out metal, cost is the big thing, not speed.
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|HEAD-FRAME, BINS, AND LEACHING-TROUGHS, HOME-STAKE MINING COMPANY. Photograph by Kadel and Herbert.|
THE INVENTION OF POWER DRILLS AND HOW THEY EAT THROUGH MOUNTAINS
The tunnel job that did most for mining was the building of the Hoosac tunnel, in Massachusetts. It was not a fast job, because work began in 1850, and twenty-five years passed before the first train ran through. In the first fifteen years, much of the work was done by hand, holes being drilled in the rock with tools held and turned by one man while another struck them with a sledge. Later, the rock was blasted out with black powder.
The year before work on this tunnel was commenced, in 1849, J. J. Couch, of Philadelphia, had invented a power rock-drill, operated by steam. Evidently he did not make it work at the outset, but with the help of J. W. Fowle, a Boston inventor, it was brought to the point where the Hoosac tunnel builders began to use it in 1867.
It struck a blow every second, five to ten times as fast as by hand. Couch and Fowle built their drill in the railroad shops at Fitchburg, Massachusetts, where a machinist, Charles Burleigh, helped them. Burleigh made several improvements, and he finally bought it from the inventors, began to manufacture it, and called it the Burleigh drill.
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|THE FIRST POWER ROCK-DRILL. J. J. Couch, of Philadelphia, in 1849 patented the first power rock-drill ever made in this country. With the aid of J. W. Fowle it was developed so that it played a conspicuous part in driving the famous Hoosac tunnel in 1867. The drill was operated by steam, and it struck a blow every second.|
Other inventors then started experimenting, among them Simon Ingersoll, who invented a power rock-drill in 1871. He was known as a mechanical genius. One day a contractor commented on the ruinous delay of much rock cutting:
“Ingersoll, you have done a good deal of inventing. I wonder whether you could invent a machine to take the place of hand labor in drilling rocks?”
Ingersoll thought a moment, then replied: “I think I see a way by which I can make exactly what you want—a machine driven by power which will drill holes rapidly in rocks.”
“That’s it !” said the contractor. “And if you show me a model that successfully works, I’ll give you $100.”
In two or three weeks, Ingersoll had built not only a model but a drill ready for work which met every test. A few improvements were made, but the fundamental idea of Ingersoll’s drill is still used to-day.
Even before the Hoosac tunnel was finished, miners began using the steam drill in Colorado. Gold had been found there in the fifties, and had been mined with pick, shovel, and hand-drill. In 1879, the discovery of silver-lead ore at Leadville started the great Colorado silver-mining industry. Power drills were needed to mine this kind of ore profitably, and inventors turned to the mines for their customers.
Men like Ingersoll, A. C. Rand, George Githens, Henry C. Sergeant and others made mine drills that were operated with compressed air instead of steam. They also made them small enough for one man to operate, and made the drill turn while running.
Rand’s drill, invented in combination with George Githens, was used in the copper and iron mines of Michigan; in 1875, and it drilled the Hell Gate obstruction in the East River, opposite New York City for the great blast that cleared it away in October, 1885.
Sergeant invented a drill between 1873 and 1878, which was used in driving many Western railroad tunnels, as well as in mining.
One of the leading inventors was J. George Leyner, a Colorado machinist, born and raised in mining towns. He began by repairing miners’ drills, and then proceeded to improve them.
Eventually, about 1897, he made the first “hammer drill,” in which the piston moved up and down, striking the drilling tool, instead of being attached to it. The drilling tool was hollowed, so that water or air could be pumped through while it was working and the rock dust cleaned out of the hole that was being drilled.
From this, inventors have gone on to smaller and smaller drills, until to-day tools of that kind are used for rivetting, hammering, chipping, and many other odd jobs. There are also drills operated by electricity.
Working with hand tools, a miner could drill from one to two feet an hour, striking fifteen to twenty blows a minute. One of the latest power drills, striking 1,750 blows a minute, and operated by one man, will bore holes in granite at the rate of eighty feet an hour. Mining journals constantly report broken records.
In a British Columbian mine not long ago, 932 feet of tunnel, measuring seven by nine feet, was bored through in a month. A crack crew of miners will bore their way through rock, driving a round hole, eight or ten feet across, at the rate of a foot an hour, including all the blasting and hauling out of broken rock—the “cycle,” as miners call it.
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|LEYNER JACK-HAMMER (Left) The modern jack-hammer was invented by J. George Leyner, a Colorado machinist, in 1897. In the jack-hammer the piston acts as a hammer. It is not attached to the drill but strikes it. The drill is hollow, so that water or air can be pumped through it to clear away the rock dust. (Right) The jack-hammer equipped with an auger for drilling horizontal holes.|
Power drills have proved so effective that much now depends upon the machinery by which their cutting tools are sharpened.
A rock-drill is a rod of very hard alloy steel, with a “bit” formed on its cutting end. These bits differ in shape according to the work to be done, but a common one is that of a cross. The cutting tool strikes the rock hundreds of times a minute, and is constantly turned to strike a new place, beating rock to powder, which is blown or washed out so that the bit may always strike clean rock.
The drills are not sharpened by grinding, but heated white hot and new cutting edges formed by hammering. When bits were sharpened by hand, it was hard to make them true, so that in fast work they cut a crooked hole, and sometimes stuck.
Also, if a miner wanted a deep hole one inch in diameter to hold his blast, he might have to start a three-inch hole, then work farther down with a two and a half inch drill, and finally finish with one inch. Much of the force of his explosive was lost in such a hole. With more accurate drills, not nearly so large, a hole is needed at the top.
Machines for sharpening drills make cutting edges of great accuracy, forming them with dies, and the blows of a power hammer, thereby doing the work much faster than is possible by hand, and more cheaply. Thus a better supply of drills can be kept ready for the miner.
Inventors are now intent upon tunnelling machines which, with many drills, will cut either holes in a circle for blasting, or hammer the whole face of the tunnel, eating their way bodily into rock. The first recorded machine of this kind was made for the Hoosac tunnel, in Boston, in 1851, to cut a circular groove in the face of the tunnel thirteen feet in diameter, and twenty-four inches in depth by revolving cutters. The machine was abandoned after cutting only ten feet.
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|East Portal, Hoosac Tunnel.|
Other tunnelling machines have been built for penetrating earth and soft rock. The Beaumont, an English invention, patented in 1864, has a record of more than fifty feet per day. The Brunton tunnelling machine, patented in 1868, and used in the chalk formation under the English Channel, had a system of cutting disks which bored a seventeen-foot tunnel at the rate of two and a half feet an hour, but its inventor died before he could develop and place the machine on the market.
In recent years inventors have been unusually active in this field, but have as yet given the miner no practical tunnelling machine, that is, one that will cut its way through hard rock.
DYNAMITE, THE MINER’S CHEAP HIRED MAN, AND ITS INVENTOR
At the time Burleigh’s drill was used in the Hoosac tunnel, a more powerful explosive supplanted black powder. It was known as nitroglycerine, discovered in 1847, by A. Sobrero. But it was an oily liquid, and very dangerous to handle.
In 1867, a Swedish chemist, Alfred Nobel, whose father was a nitroglycerine manufacturer, learned how to make it safe to handle. He soaked the explosive in earth or wood pulp, forming a cartridge and thus giving dynamite to the tunnel builder, and soon after to the miner. Dynamite is the strong, cheap hired man of the miner, the engineer, the contractor, and even the farmer.
Nobel also invented blasting gelatine by mixing nitroglycerine with collodion. After making millions of dollars out of explosives for peaceful work, Nobel, of pacifist tendencies, feared that the products of his genius would be used in war. So upon his death, in 1896, he left a fortune of over $10,000,000, the interest of which is distributed in prizes every year to men who have contributed most to the benefit of mankind during the previous year.
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What did man do without explosives? He used his head more than people suppose. He learned to build a hot fire against an ore vein, and then douse it with water, a procedure that usually cracked off a lot of ore. If he mined in a cold climate, he poured water into cracks in the rock; the water froze, expanded, and broke off ore-bearing rock. Another of his methods was to drive soft wooden wedges into cracks, and on soaking these wedges with water the rock was broken off as they swelled.
With one blast of powerful explosive to-day, the metal miner breaks up ten to twenty-five tons of ore, an amount which would have taken several days to smelt before the dawn of dynamite.
In the silver and copper mines of South America there were hundreds of Indian ore-carriers, who, carrying the ore on their backs, climbed notched poles out of the mine long before Columbus discovered America. This they do to the present day in many of their mines.
But in modern metal mines of to-day, there is wonderful hauling and hoisting machinery to do all this back-breaking work.
HOW THE ORE IS SEPARATED
What miners call “separation” is getting the metal out of the rock after it is mined. The first method was to build a fire and achieve “separation” by melting, but the ore had to be rich for that. Modern methods permit metal to be taken out of ores that are very “lean.”
Fire would never melt it out cheaply enough; instead, water does the extraction on the same principle as did the old California gold miner’s pan. On an enormous scale, machinery washes out the lighter dirt and rock. The ore, if in solid rock form, must first be ground to dust, so that the particles of metal may be separated by water. This system yet remains a great field for inventors.
The Egyptians and Romans had crude ways of pounding gold-bearing rock, keeping thousands of slaves at that work. They invented the first stamp mill; a stone mortar with an iron pestle, to break the rock. Somewhat better stamp mills were used in Germany in the fifteenth century, and in the famous mines of Potosi, Peru, in the sixteenth century, where the first stamp milling in the western hemisphere was done.
But the discovery of gold in California marked the real beginning of “separation.” A crude stamp mill had been used at Tellurium, Virginia, in 1865, and later others appeared in Georgia. With labor costly in California, machinery was clearly needed for crushing.
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One of the first mills there was built by William S. Moses, who brought his knowledge of ironwork from Georgia. These early stamp mills were run by water power. California, with its huge mining industry, stimulated inventors, and men like C. P. Stanford, J. Fish, J. Wheeler, and H. B. Angel mechanically improved the stamp mill during the fifties and sixties, developing a machine which has come to be known as the “California’ mill,” the stamp mill of to-day.
Emulating the Egyptian slave, it picks up a weight and drops it, crushing the ore. The modern mill has many stamps, often of great weight, which are lifted and dropped by ingenious cam mechanism, designed to reduce wear and to increase the crushing effect, and run by water-power, steam, or electricity.
Different kinds of ore have to be powdered in different ways, and as ores get leaner and leaner, they must be ground finer. Men have built almost every kind of machine to do this work: pounding, crushing, and rolling-machines, also great steel cylinders in which ore is placed with a lot of flint pebbles or steel balls, or bundles of steel rods that roll over and over, finally pounding it into dust.
Usually, this grinding is done with a series of machines, one kind breaking the ore into small bits, another reducing it to sand, and the last one making it so fine that, ground to powder, it can be sucked out of the mill by vacuum, like dust out of a carpet.
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|GATES ORE-CRUSHER. This is a crusher in which the reciprocating jaw of the ordinary machine is supplanted by a gyratory crusher moving in a vertical conical shell; it was patented in 1881 by P. W. Gates. The machine is capable of breaking two to four tons of compact gold quartz an hour. Courtesy South Kensington Museum.|
For many years California gold ores were rather crudely ground in stamp mills, and washed over tables where mercury caught the gold particles and held them in an alloy. Mercury, among man’s oldest metals, is also called “quicksilver,” because it is liquid until brought down to nearly 38 degrees below zero, Fahrenheit. It is really a metal in molten condition at ordinary temperatures.
The ancients were familiar with mercury at least 700 years before Christ, and they learned that it had the peculiar quality of mixing with many other metals without their having to melt them.
Mercury dissolves gold, silver, copper, tin, lead, and other metals when it touches them. The ancients used it to catch gold in much the same way as the California miners did, later. They also dissolved gold in mercury for gilding. Putting mercury that had caught gold into a bag of chamois or canvas, they twisted and squeezed the bag, forcing the liquid mercury out through the fabric, leaving the gold inside.
The California miner used this method, too. The use of mercury to catch gold is called “amalgamation,” and for centuries it was the only gold-recovering process known, with the exception of simple washing.
Then, inventors developed ways of doing the work better with chemicals. Where the ancients were satisfied with an extraction of forty to forty-five per cent. of gold and silver, the chemist got ninety per cent.
CHEMISTRY AIDS SEPARATION
Chlorination, by which the power of chlorine gas was utilized to turn metallic gold into a chloride, after which it was dissolved out of that chemical by water, was applied by a German, C. F. Plattner, in 1848. An Englishman named Percy made the same discovery in 1849.
The process consisted in grinding the ore to dust and then roasting it in a furnace, a procedure that turned all metals other than the gold or silver into oxide. The chloride failed to affect either the gold or silver, which rare metals were then washed out by water.
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A better system is the cyanide process, developed in South Africa to extract gold from stubborn ore that could not be profitably treated either with mercury or chlorine gas.
In the Middle Ages it was known that cyanide of potassium would dissolve gold in water. No way was found to use the discovery commercially until 1890, when MacArthur and Forrest, in South Africa, took out a patent for a cyanide process, which is now employed in gold and silver mining.
Ore for cyanide treatment must be ground very fine. It is then put into tanks containing cyanide dissolved in water. The chemical takes up the gold and silver; the rock dust and liquor are separated; and electricity is utilized to make the liquor give up its precious metal.
A cyanide plant is a place of enormous tanks, filters, and other contrivances for dissolving gold and silver. The slime of rock dust is easily separated, and tons upon tons of material are daily handled with as little hand work as possible, everything flowing through the different machines like water running down hill.
But this would not do for metals like copper, zinc, lead and tin. For years, they had to be separated by gravity—as most of them are to-day. The fine particles of metal are heavier than the particles of rock, with which they are mixed after grinding. This dust falls into a stream of water, and is carried along over separating tables of so many different kinds that one can hardly remember them all after visiting a milling plant.
The water with its ore flows from table to table. Each table is jogged up and down or sideways, and its motion causes the heavier metal particles to sink a little lower than the rock dust, which flows one way, while the metal is caught against ridges and flows another. Each table catches some of the metal, and what particles get away are partly caught by the next table, and so on, until, water separation having done its best, the residue flows away to the dump.
Miners, however, knew that there was still wealth in the dump, if they could only get it out. There it lay, after all the work of mining the ore and grinding it up. If some new process could be found, the stuff was ready for the mill, with no more expense for mining or grinding.
Then came the latest marvel of metal mining, a process called “oil flotation”; also the “frothing” or “bubble” process. A great costly dispute has grown up about its invention, and scientists also disagree in trying to explain how it works. By this process, copper, zinc, lead, gold, silver, molybdenum, graphite, and other minerals are extracted or separated from 60,000,000 tons of ore a year in this country alone.
In water separation, the fine particles of metal sink because they are heavier.
In oil separation they float! Powdered ore is churned with oil and water until a froth is made, and in some miraculous way, the fine particles of metal cling to the oil bubbles by what scientists call “surface tension,” and are lifted and floated away as though they were clinging to a life-buoy.
The particles of powdered rock do not cling to the bubbles. Surface tension is the force that enables insects to run on water, and a needle to float on water. It is a kind of skin; an intangible skin of force.
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|SECTIONAL MODEL OF A FROTH FLOTATION PLANT. This is a method of ore concentration of rapidly increasing importance, whereby metallic sulphides in an ore pulp are separated by flotation. The method is based on the property that certain sulphides have of selectively attracting oils and greases, hence the mineral particle becomes surrounded by an envelope which lowers the specific gravity on the whole sufficiently to render it capable of floating on water. Courtesy South Kensington Museum, London.|
Many kinds of oil are used. The process was first developed on a large scale in Australia, and oil from the eucalyptus trees of that country did the work. The United States is a petroleum country, and when oil flotation was introduced here, mineral oils and some vegetable oils, such as are obtained from the pine-tree, in making turpentine, were found satisfactory.
Different oils work best with different metals and different ores. Naturally, the cheapness of the oil is an important point; for although a pint of oil, by its wonderful bubbles, treats many tons of ore dust, the quantity required to treat millions of tons may run into a great deal of money.
A woman had a hand in this invention. She was Carrie J. Everson, of Denver, Colorado, a doctor’s wife, and she took out a patent in 1886. While washing some oily ore sacks, according to one story, she noticed that oil would stick to metal particles and float them. Another account says that she made this discovery by laboratory experiments.
Herodotus, the Greek historian, knew that oil would float particles of metal, and, like him, Mrs. Everson neglected to make a working process out of the discovery. Before she washed those ore sacks, and since that time, other people had noticed this action of oil upon metal particles—so many of them, in fact, that great lawsuits have been fought over the matter.
Oil flotation really went to work for the metal miner when it was found that the bubbles were even more important than the oil, and some people think “froth flotation” a better name than “oil flotation.”
Oil flotation was first actually used on a working scale at a mine in Wales, by Francis E. Elmore, in 1899, and he patented his process in 1901.
Its first use on a large scale was in Australia, in the famous Broken Hill mines, where three English inventors, H. L. Sulman, H. P. Picard, and J. Ballot used a process which they had patented in 1905, by which they extracted eighteen per cent of zinc and seven per cent of lead from 12,000,000 tons of mine waste.
About 1910, it was introduced into the United States. Used in the same way, it recovers from mine dumps the metal thrown away in days of cruder methods, and extracts as high as ninety-eight per cent., from freshly mined ore.
FINDING WEALTH IN OTHER GENERATIONS’ LEAVINGS
A fascinating trend in modern mining is to get wealth out of other generations’ leavings. Inventors are constantly studying its accomplishment. Ancient miners rejoiced if they got even half the metal out of ore or gravel, but a few generations after they were dead and gone, other men, better miners, would work over their heaps of “tailings,” and get more metal.
The Romans mined silver on the island of Sardinia, leaving great piles of waste behind. Balzac, the French novelist, was told about these mine dumps by an Italian merchant, and dreamed of getting rich by extracting the silver the Romans had left.
But before he could go to Sardinia, the merchant, taking the hint, got the right to work over this mine refuse. It yielded ten per cent of lead, and there was ten per cent pure silver in the lead. To-day, oil separation might make it profitable to work over that refuse again.
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In brief, this is the story of mining everywhere. First, the loose metal lying on the ground is picked up, then the richest veins are found and worked, then those not so rich, until a time comes when man must use all his wits, inventing ways to work leaner and leaner ores.
This happened in our own Western country. Finer and finer grinding, better and better separation were needed every year until, toward the close of the nineteenth century, methods had been brought to a point where an American mining genius stepped in and did a startling thing.
Daniel C. Jackling, whom mining engineers declare to be more of a manufacturer than a miner, decided that, instead of digging into a mountain and following a vein of metal, he would pull a whole mountain down and grind it up. Out in Utah there was a whole mountain of porphyry rock which contained a very small proportion of copper, two per cent, and even less. There was a lot of it in the mountain, however.
Jackling proposed to clear away or “strip” the thirty or forty feet of earth off the top of the mountain, drill down into the rock and blast it to break it up into sizeable lumps, shovel it onto railroad cars with steam shovels, and then grind and separate the copper on an enormous scale.
It took several million dollars to build a railroad and an ore mill, but it paid in the end. Mining began in 1904, and Utah Copper has been so successful that other great porphyry copper mines are being similarly worked in this country and South America, as also is gold ore in Alaska, so lean that profit means the difference of ten and fifteen cents a ton in the gold recovered as it passes through the mill.
Jackling was once asked what had given him the most satisfaction in his career, and he answered in figures, saying that when he began pulling down his first mountain, all the copper mines in the United States produced 900,000,000 pounds of copper a year, while to-day the low-grade mines alone, if those in South America are counted too, produce more than that.
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|GENERAL VIEW OF UTAH COPPER COMPANY’S MINE. This is one of the large porphyry mines of the United States. The mine owes its existence to the daring and energy of Daniel C. Jackling. The mountain in the picture is composed of porphyry rock containing two per cent, and less of copper. Jackling conceived the idea of tearing down this mountain and grinding it up into powder from which this almost infinitesimal percentage of metal is recovered. Courtesy United States Bureau of Mines.|
One would think the limit had been reached in this sort of mining. Yet, still more wonderful is the gold-dredging method of placer mining, where a ton of rock and dirt is sorted over to get less than ten cents’ worth of the precious metal.
Placer mining is limited mainly to gold and platinum. Most metal mining is done by piercing mountains or tearing them down. Placer mining deals with mountains that were torn down by nature herself ages ago, carried away by rivers, and heaped up in gravel beds.
Sometimes these beds have rich deposits of gold on top of them that men can wash out by hand. But the rich top soil is soon worked, and it takes mighty machinery to go through the many feet of gravel beneath, gravel that bears only a trace of gold to the ton.
Gold may be found all the way down to depths of fifty or a hundred feet, and even more. It is possible to build dredges that will bring it up from such depths, but below sixty or seventy feet these machines must be so big and costly that it would probably not pay.
This kind of mining has its prospector. He is not like the prospector who seeks mineral veins in the mountains. In this case, prospecting is done by a crew of men and horses with a well-drilling machine.
They go to an old river bed, where gold has already been found, and begin drilling holes about six inches across, and examining the gold found in each foot of ground as they go down to depths of twenty-five or fifty feet. They are thus able to find where there is gold enough to pay for dredging, and also to reject ground where rocks and boulders would make dredging too expensive, if not impossible.
The gold dredge is then built in. It is a great barge or scow, sometimes of wood, but more often steel, upon which is erected machinery for turning an endless belt of massive steel buckets. Through the West where there is plenty of water-power, electricity—generated by a waterfall—is used to run the machinery.
Gold dredges were first tried, with success, in New Zealand as early as 1865, and steam-shovel dredging was attempted in California as early as 1888. The first successful gold dredge in this country was used on Grasshopper Creek, Montana, in 1894.
At first, “spoon” dredges were used, iron spoons weighing a thousand pounds, at the end of a long pole, being dragged along the river bottom with rope and windlass. The dirt they brought up was washed by hand in rockers. Modern dredges have huge steel buckets in an endless belt, an idea first used by an inventor named Scott, in New Zealand, in 1882.
The first successful dredge in this country, a bucket-lift dredge, was used in Montana. California quickly developed gold dredges. The first California Yuba dredge—so called after the place where it was first tried—cost $25,000. The biggest and latest dredge to-day costs $600,000.
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|THE YUBA GOLD DREDGE. Huge dredges, such as this, make it profitable to dig up the soil of ranches and orchards in California in order to recover a few grains of gold in a ton of dirt. The gold dredge is a great barge or scow upon which is erected machinery for driving an endless belt of steel buckets by which a steady stream of material is dumped on separating screens. A complex system of riffles and sluices then separates the gold. Such a dredge may cost $600,000. Profit means the difference of ten or fifteen cents a ton in the gold recovered as it passes through. Courtesy United States Bureau of Mines.|
The dredge is a boat, but it does not need a river to float in at the beginning. Almost any creek will do. It is brought to the spot in pieces, and set up on dry land. When ready, it reaches out and down to the ground, and begins digging a hole with its line of manganese steel buckets, each weighing two to three tons.
The dirt and stones are piled up to make a dam behind it, and before long the water from the creek has filled the hole, and the dredge is afloat. After that, it can go anywhere through dirt or gravel by simply digging its own channel.
These dredges handle dirt and gravel at a cost as low as two cents a ton. Their buckets bring in a steady stream of material and dump it upon screens. The big stones are fished out, then the smaller ones, until finally nothing but the gold-bearing sand is left. That goes to a complex system of riffles and sluices, where quicksilver catches the almost invisible particles of the rare metal.
With electricity for power, a big dredge can be operated by only four or five men, and in a region large enough for profitable gold-dredging, may have twenty or thirty years’ work ahead of it. Very often it strikes a place where trees had grown over the ground, and then men are sent ahead to cut them down.
Placer mining, both by giant streams of water and dredges, at first left the ground so tossed and tumbled with stone piles and boulders that, although the soil was fertile enough in the beginning, it was useless to the farmer who might come later.
This led to so many complaints against placer mining that now the latest gold dredges have “stackers” similar to the stacker of a threshing machine, that carry off the gravel and dirt, and spread them evenly behind as it slowly moves along. In this way the incoming farmer finds the soil ready-made for him.
Gold is the chief metal secured by dredging, but machines also bring up small quantities of platinum and other scarce metals, and have even been used in tin mining. A gold dredge in Brazil was found to be on diamond-bearing ground, which set the dredgers excitedly watching for precious stones amongst the pebbles sorted out.
Diamonds were first found in river beds, then traced back to the “pipes” of earth and stone where they had come from, and these “pipes” are developed as diamond mines. For several centuries diamonds had been found in the streams of Brazil, but no prospector ever followed them up. Not long ago an American geologist showed that Brazil has diamond pipes just like the famous ones in South Africa.
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THE SCIENTIST AIDS THE MINER
The geologist believes that his science will be most important in the mining of to-morrow. Already, this is being proved correct. The inventor gave the miner marvellous machinery for getting ore out of the ground and extracting its metal. The engineer brought steam-shovels and railroads on the job, making it possible to mine on an enormous scale. The chemist has helped with his cyanide and other processes, among which is the interesting “tin can” process, used to take copper out of mine water.
It was learned that water pumped from the great copper mines in Butte, Montana, contained copper which would be valuable if there were any way of getting it out. Chemists knew that water liked iron better than copper, and that when iron was put into water carrying copper, it would drop the copper and take away the iron.
So the water from these mines is pumped into great troughs in which old scrap iron— anything from a battered tin can to a discarded steel rail—is dumped. Little by little this old iron changes into a soft, rusty-looking substance, which is later turned to copper metal by heat, at the copper smelting plants. The water drops copper worth fifteen to twenty-five cents a pound, and takes away old iron worth perhaps a cent.
Much of the metal won from ore must finally be smelted and refined, for it is usually mixed with impurities or other metals. This is done at smelting plants, far from the mine as a rule, because the metal dust, or “concentrate,” washed out of rock dust, can be hauled long distances.
Some metals, such as lead, silver and zinc, though mixed together, are separated by heat, for they have different melting points: lead, 621 degrees Fahrenheit; zinc, 787 degrees; silver, 1,761 degrees.
There may be very small amounts of other metals mixed in copper, such as gold, silver, or platinum. These are too small to melt out, so they are extracted by electrical refining, in which the crude copper pig from the smelter is used as an anode in an electric battery, and, gathering on the cathode as pure copper, drops its gold, silver, platinum or other metals in the battery solution from which they are afterward recovered.
The geologist feels that his science will take out of mining many of the failures, losses, and false moves. Studying the rocks as nature has placed them around the world, he believes that he has learned how some of the valuable metals are put away in her storehouse; in other words, he knows where to look for the needle in the haystack.
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Investigations are constantly being made by government scientists connected with the United States Geological Survey and Bureau of Mines, as well as government scientists in other countries, to discover general principles for mining engineers to follow.
Geology is a new science, hardly a hundred years old. Mining geology is even younger. Thirty or forty years ago miners paid little attention to geology, and geologists could tell them almost nothing about mining. But by studying the arrangement of different kinds of rocks, and observing how nature places metals in them in the same way in different parts of the world, gathering a great many facts, and putting two and two together, the geologist is already able to aid the miner with truly scientific knowledge.
He cannot yet say positively that one mountain contains copper, and that it will be a waste of time and money to look for copper in another. But he can say with probable accuracy, that a certain mountain contains copper, that it is likely to be found in a certain kind of rock running through the mountain, and that it runs in such and such directions because the mountain was built in such and such a way.
Already he has learned enough to know that mining can be made a science instead of a gamble, and its development on scientific lines depends upon gathering still more facts, and learning the lessons that facts always teach when they are studied intelligently.