Fabulous wealth has been extracted for centuries from the rich and unseemingly unlimited silver mines of South America and Mexico. The comparatively recent discovery of the metal in the United States and in Canada gave rise to modern scientific methods of refining
AT BROKEN HILL, in New South Wales, there was discovered in 1883 an outcrop of one of the richest silver-lead-zinc ore deposits in the world. The ore has yielded more than 480,000,000 ounces of silver, but only lead and zinc are now yielded in large quantities. Lead concentrations are sent by rail to Port Pirie, South Australia, for refining.
THE greater part of the world’s production of silver is mined in North and South America, and most of it is absorbed by China and India. To hundreds of millions of people in the East silver, not gold, is the standard of money value and of prosperity. When the Indian peasant is prosperous he buys silver ornaments for his womenfolk. The craft of the silversmith is not, however, confined to the East, nor is the use of silver as a medium of exchange.
In the West, although gold has been withdrawn from circulation, silver bridges the gap between paper money and copper coins. From time to time the price of silver has fluctuated so widely that buying power all over the globe has been crippled, causing widespread economic trouble.
The word “dollar” is a money symbol that is almost universal. It originated from the coins minted at Joachimsthal, in Bohemia. The coins were called Joachimsthalers, then thalers and finally dollars. Greece, Spain, France and Great Britain were mined for silver in ancient times, and Germany and Austria in the Middle Ages. In 1519, the year in which, according to tradition, the first Joachimsthalers were minted in Europe, Cortes landed in Mexico. He and his men saw such lavish displays of silver and gold that their cupidity was aroused and they seized the country, overthrowing the Aztec rulers. For similar reasons the Inca civilization in the Andes of South America was crushed by the Spaniards under Pizarro.
During several centuries the Indians of Mexico and of what are now the Republics of Peru, Chile, Colombia and Bolivia were virtually slaves of the silver mines. Nobody will ever know how much silver was mined and sent to Spain during the three centuries she retained her grip on Central and South America. Nor can any one say how the Indians learned to mine and refine silver, and then work the metal with considerable artistic skill, long before the Spaniards arrived. Silver is universally admired as one of the most beautiful of metals. The craft of the silversmith delights all who appreciate the art of worked metal.
Whether as a personal ornament in the East or as tableware at a London banquet, silver is esteemed for its artistic appeal. Its ductility and malleability, exceeded only by that of gold, and its brilliance when polished have attracted the smith from the earliest times. It is the best known conductor of heat and of electricity, although its cost prohibits its use on a large scale for these purposes. In the form of numerous compounds silver has a variety of uses ranging from photography to the dyes industry. For use as money it is hardened by alloys, the proportion of silver varying according to the price of the precious metal.
Sometimes, particularly in Mexico in the early days, huge lumps of pure silver have been discovered. The largest mass ever found was a huge lump weighing 2,750 lb, (over a ton) discovered in Mexico. Another huge mass, weighing nearly three-quarters of a ton, was found at Kongsberg, Norway, where the metal has been mined for about three centuries. Silver is generally found combined with sulphur, arsenic and sulphur, antimony and sulphur, tellurium, chlorine and so forth, and with metals such as lead, copper and mercury. Sometimes the ores are so complex that until recent years they have baffled the refiner. The engineer and the chemist have solved these problems and have transformed mining and refining, so that many mines now in operation would not pay by older methods.
Production of silver varies considerably. In 1936 about 250,000,000 fine ounces were mined; of this total no fewer than 168,000,000 fine ounces were produced by America. Mexico is still the greatest storehouse of silver, despite centuries of large-scale mining. Production has varied greatly in the last century because of civil strife.
So rich was the country in silver when the Spaniards conquered it that they were not concerned with intricate mining problems. If they encountered difficulties in one mine they abandoned, it and opened up another, there being plenty of mines from which to choose. The peons, or labourers, dug shafts down which ladders were fixed. The mined ore was put into a bag made of raw hide. The peon slung this bag on his back and mounted the ladder rung by rung. When water entered the workings it was ladled into raw hide buckets and the peons climbed the shaft with these and tipped the water out. If this human pump failed to keep pace with the inflow of water the mine was abandoned.
The Mexican Process
Considerably more thought was required to evolve a process for crushing the ore and extracting silver from it. The patio, or Mexican process, which was invented in the sixteenth century, was so suitable to the country and the conditions that it was supreme for centuries. It depends on the use of mercury, which amalgamates with silver, thus separating the precious metal from its compounds.
The ore from the mine is sorted and broken into lumps by men and women with hammers. The next step is to crush the ore in stamping mills, the motive power for these being supplied by mules. At this stage the ore is taken to a crushing mill to be reduced still further by being ground. Then water is added gradually until a t hick mud is formed.
The mud is taken to the patio, a carefully paved floor, where a process lasting for many weeks begins. Salt, acid, lime and mercury are added and the mixture is trampled by mules for weeks until the overseer decides that the mercury has amalgamated with the silver. The mixture is taken to water troughs and the dross is washed away, leaving the amalgam of mercury and silver. This is distilled, the mercury being used again for the process and the silver cast into ingots.
The efficiency of the patio method depends largely on the skill of the overseer. It is claimed that from 75 to 90 per cent of the silver can be recovered. The earlier workers were not exacting. The mud that they had discarded was used for building houses for the peons. In recent years companies have bought up these buildings, knocked them down and extracted sufficient silver from them to yield handsome profits.
Those miners who had engineering ability reaped fabulous rewards. In the middle of the eighteenth century two men went into partnership and drove a great adit, or drainage tunnel, through the side of a hill until it tapped old workings which had been abandoned because of the water which had flooded them. One of the partners, Pedro Terreros, afterwards the Count of Regla, became one of the richest men in the world.
The mine, the Real del Monte, became famous. The adit was about 9,000 feet long and was a wonderful work for those days. The count made millions of pounds. After his death, however, the newer workings reached far below the level of the adit and water began to flood them. Those in charge adopted a crude system of pumping the workings by drawing the water in skins to the adit, with mules as the motive power; but gradually the cost almost equalled that of the value of the silver. Then came the Mexican War of Independence, and after this Mexican silver mining entered a new phase.
3,000 FEET BELOW THE SURFACE miners drill holes for blasting silver-bearing ore in the mines near Butte, Montana, in the United States. Silver was discovered in the United States in 1859 by prospectors in the State of Nevada.
At this period the British engineer was beginning to alter the world, and British money was seeking an outlet. Many people had the idea that they would make easy fortunes out of Mexican mines and they subscribed a total of about £10,000,000, which was eventually lost. The Real del Monte absorbed about £4,000,000 of this. The chief cause of loss was the cost of pumping water. Instead of following the excellent example of the two Mexicans and driving an adit to tap the workings, the British cleaned the old adit and tried to pump water into it from the bottom of the workings with steam engines. They also sank a new shaft and drove new galleries, but the water won.
Although they did all they could the men failed, because the steam engines of a century ago could not pump out the vast quantities of water. The company sold all the machinery for a small sum. The British engineer of the new company then drove a new adit over a mile, mostly through hard rock, far below the original one, and tapped the flooded workings. The water flowed down the gradient of the adit and the workings were drained. Once again the great Mexican mine began to yield silver at a profit.
In the Mexican mines the extraction of the ore and its dispatch to the refinery were only part of the problem. Because of the unsettled state of the country each refinery had to be turned into a fortress guarded by armed men, ready to beat off the attacks of bandits. Armed guards had to accompany each convoy of silver to the coast ports from which it was shipped.
Few chapters in the story of mining are as remarkable as the discovery of silver in the United States. In 1859, ten years after the California gold rush, two men, named McLaughlin and O’Riley, were prospecting in the State of Nevada.
Silver Rush in the U.S.A.
They found gold mixed with “black stuff”, which puzzled them. Another adventurer named Henry Comstock joined forces with them. Their work was hindered by a seam of black rock. Soon the “black stuff” came into the hands of an assayer, who found that it was silver ore. The news spread and the silver rush began.
Adventurers swarmed over the mountains late in 1859, but had to wait until the following spring before they could get to work in that bleak area. They dug out the ore but could not refine it. An enterprising engineer, however brought plant over the mountains and set it up in the district at Washoe, Nevada. He reduced the ore by an amalgamation process which became generally known as the Washoe process.
By the time that the miners’ diggings became deeper as they followed the lode into the earth, they were confronted with engineering difficulties which stopped them. Then they halted until a skilled mining engineer arrived and taught them a system of timbering which enabled them to work without the risk of being buried alive. Meanwhile roads were built across the mountain ranges.
Stage coaches raced over the mountains from Virginia City, Nevada, to Sacramento, California, and a colourful period began. Individual mining gave way to planned mining and vast fortunes were made in a few years — until the deep workings became flooded and the old problem which had arisen in Mexico presented itself in Nevada.
REAL DEL MONTE SILVER MINE, near Pachuca, in the province of Hidalgo, Mexico. This mine was reopened in the middle of the eighteenth century by Peter Terreros, later Count of Regia, who became one of the richest men in the world. His first adit was driven to a length of about 9,000 feet and was a remarkable engineering feat for the period.
It was proposed to drain all the mines by a great adit. The drainage tunnel would have to be driven four miles from the Carson Valley. At first the owners of the various mines saw the logic of building one tunnel to drain all the mines by gravity instead of trying to pump the water vertically out of each mine by separate pumping plants.
With imperfect tools the work was extremely arduous. The tunnel was planned to enter the lode about 2,000 feet below the surface and the heat was exhausting, the temperature of the rock sometimes being 114 degrees. The rock was put into trucks which were pulled along a tramway-track by mules, and the air was so bad that even these hardy animals had to be forced into the far end of the tunnel. Air was blown into the tunnel through canvas hoses, and sometimes a mule put his head into the opening of a blower and had to be pulled away. When the tunnel was completed in 1878 it was one of the engineering wonders of the world. But so many years had been wasted by opposition that by the time it was completed most of the ore had been mined.
While the men were driving the tunnel into the hill a fortune was dug out of one mine alone. Four men spent £40,000 on sinking a shaft and were nearly bankrupt when at last they came to rich ore. Each of the four was a millionaire in a few months, and the mine was producing ore worth millions of pounds for a number of years.
Silver was discovered on War Eagle Mountain, Idaho, after the discovery of the Comstock Lode. This discovery led to serious fighting between two rival mines and the disturbance had to be quelled by troops. The Government proclaimed martial law and sent troops to restore peace.
Farthest North
Further discoveries of silver were made in Nevada. One party of prospectors found a mine which they sold for £100,000. Soldiers, pursuing Red Indians, discovered other mines. California, Arizona and New Mexico soon began to yield the metal.
The discovery of silver at Cobalt, Canada, is described in the chapter “Canada’s Mineral Wealth”. Canada’s silver is produced chiefly by British Columbia, new processes having made it possible to refine the complex ores of the great Sullivan Mine. Silver is often so associated with other ores that it is one of a number of products of one mine.
Perhaps the most remarkable mine of this character is the new one on the shores of the Great Bear Lake at a point a few miles south of the Arctic Circle, where a little community of a hundred men has arisen to work in America’s farthest north mine. Silver, copper and silver-radium ores are being raised at the Eldorado Mine.
Although the silver is profitable the main reason for the mine is radium. A few years ago two prospectors landed in the neighbourhood by aeroplane, and pitchblende was discovered. Before this discovery the largest known deposits of pitchblende were near Katanga, in the Belgian Congo. Development of the Canadian deposits has enlarged the world supply of radium and greatly reduced the cost. The silver and copper concentrates from the mine are sent to Tacoma, Washington, to be smelted, and the silver-radium to Port Hope, Ontario.
In what is now Bolivia, but was formerly Peru, the silver mines of Potosi, at an altitude of over 13,000 feet, have produced silver worth millions of pounds. Peru is the third largest producer of silver, much of which is extracted from the copper ores of the Cerro de Pasco region and from lead ores at Morococha and Casapalca. Cerro de Pasco is on a railway, at an altitude of 14,380 feet.
This railway carries the ore to one of the largest refining plants in the world, at Oroya, from which runs the railway to Callao, described in the chapter “Across the Andes”. The Incas mined silver in the Cerro de Pasco region and smelted it in small furnaces. The Spaniards took over £100,000,000 of silver from the mines. They sent it to the coast, then shipped it to Panama, where it was sent over the isthmus to the Atlantic shore and loaded into ships which sailed to Spain.
Broken Hill, the mining town on the western border of New South Wales, brought Australia into prominence among producers of silver. In 1883 was discovered the outcrop of what later proved to be one of the greatest deposits of silver-lead-zinc ore in the world. Ore mined at Broken Hill has yielded about 480,000,000 ounces of silver, apart from huge quantities of lead and zinc, but silver is no longer mined there. Lead concentrates are sent 254 miles by railway to Port Pirie, South Australia, where there is one of the most modern refining plants in the world. Some of the zinc concentrates are sent to Risdon, Tasmania, for treatment, and some to Great Britain.
AT AN ALTITUDE OF 14,380 FEET, in the Cerro de Pasco region of Peru, silver is extracted from copper ores. This open mine was worked by the Spaniards and the Incas whom they subjugated. To-day a railway (see page 259) carries the ore to the refining plant at Oroya.
