History of precious metals production
People have been mining gold since the Copper Age, about 6 thousand years ago. Egypt was the first gold-mining state in the world. The Ancient Egyptian gold deposit located in Nubia between the Red Sea and the Nile is considered the most ancient. In the Ancient Egypt the first gold has been mined from the placer deposits by the gold-bearing sands washing through the cloth.
During the age of the Roman Empire the gold deposits with low precious metal content in the rock have often been developed. At these deposits the Ancient Romans had to handle the task to process a huge amount of rock to recover as much gold as possible therefrom. Consequently, they invented a fairly simple method of gold production. It consisted, firstly, in making tunnels in the gold-bearing rock and putting supports and bulkheads therein. When the supports were removed the rock collapsed by gravity and crushed. The crushed gold-bearing rock was thoroughly washed with water from artificial ponds.
After the fall of the Roman Empire, during the Middle Ages, very small amounts of gold were produced and the gold production technology did not significantly change. In the 16th century the application of the amalgamation method began. It became possible thanks to the existence of Almadén, a huge mercury deposit, in Spain. This method included mixing the wet crushed rock with mercury and subsequent grinding in the breakers. The gold amalgam, a combination of mercury and gold, was extracted from the produced sludges by washing and after that the mercury was eliminated from the collected amalgam and used again.
With the acceleration of the scientific and technological progress, the gold mining started to grow in intensity anew in the mid-19th century. About since the year 1890 the hydraulic method has been used along with the cyanides application method. This has substantially reduced the cost of production and improved the quality of the produced gold.
Since the 2nd to 3rd millennium BC the gold has already been mined within the modern Russian Federation territory. The metals were extracted from the placer deposits by gold-bearing sands washing on the animal skins with hair trimmed (for gold grain capture) as well as using the primitive channels, trays and ladles. The metals were extracted from the ore by the rock heating until puffing with subsequent crushing of boulders in stone mortars, abrasion in the millstones and washing. Then the product was split by size in the sieve baskets.
Silver is one of the most ancient metals known to man. The history of the silver began with its production which originally was the search of nuggets. Though there is 15 times more of it in the Earth crust than gold, the latter is 5 times more often found in the form of nuggets: it is more chemically inert while the silver is usually a part of chemical compounds.
Due to that silver was more precious than gold in antiquity. Later, however, when the lead, zinc and silver ores processing was mastered, there became more silver in the world than gold and its relative value decreased.
The first items made of silver have been found in the Ancient Egypt. It appeared there in pre-dynastic period about 5 thousand years BC. Afterwards, the silver production began in Greece: the mines of Laurion produced the bulk of the metal over the 6th to 5th centuries BC. Later, since the 4th century BC, the mines of Iberian Peninsula controlled by the Phoenicians, first of all by Carthago, the largest Phoenician place, were on top, and after the Punic Wars and defeat of Carthago Rome took the leadership along with the control over Iberia. The silver mines appeared thereafter in almost all of the countries of Europe.
However, by the end of Middle Ages most of the native silver deposits were exhausted. The silver extraction from the ores began to play the dominant role.
The problem was solved during the Age of Discovery. The New World became an endless source of precious metals from Europe. Mexico became the main production area. 205 thousand tons of silver, about one-third of the world output, were produced there between the years 1521 and 1945. South America, the region of Peru and the Viceroyalty of La Plata the name of which means “silver” in Spanish, were not far behind. The name of Argentina, the state emerged in its territory thereafter, also implies the same meaning (Latin argentum — silver).
However, there were little precious metals by nature in Russia. The situation was so acute that for some time the foreign coins that got into the country as payment for the exported products were remelted to mint its own coin.
But in course of exploration of Siberia and Far East, Russia took control over the lands more rich in precious metals. In 1704 the regular silver mining began at the mines of Nerchinsk in Zabaykalsky territory. The deposits were also found in Altay. However, the full-scale silver mining in Russia only began after the industrialization, in the mid-twentieth century.
“White gold”, “Rotten gold”, “Frogs’ gold”... These are the names of platinum in the literature of the 18th century. This metal is long known, people were finding the white heavy grains of it during the mining of gold. However, it could not be worked and because of that it could not be employed anywhere for a long time.
This most precious metal was thrown out into disposal areas along with the empty rock and in Urals and in Siberia the native platinum grains were used as shot until the 18th century.
In Europe the platinum has been studied since the mid-eighteenth century when Antonio de Ulloa brought samples of this metal from the gold deposits of Peru.
The grains of white metal that people were unable to melt or crack on the anvil were brought by him to Europe as an amusing phenomenon... The studies followed along with the disputes: was platinum a simple substance or a combination of two known metals: gold and iron, as Buffon, a famous naturalist, thought.
The counterfeiters were the first to find a practical application for this metal in the mid-eighteenth century.
The platinum was then twice lower in value than the silver. Its density is high, about 21.5 g/cm3, it can be easily alloyed with gold and silver. The counterfeiters took advantage of it by alloying platinum with gold and silver in jewelry first and in coins afterwards. When the Spanish Government found that out, it declared war against the platinum debasement. The royal decree was issued ordering to destroy all platinum produced together with gold. Pursuant to this decree the officials of mints in Santa Fe and Popayán (Spanish colonies in South America) regularly solemnly drowned the collected platinum in the rivers of Bogota and Cauca in the presence numerous witnesses.
It is believed that Watson, an Englishman, was the first to produce pure platinum in 1750. In 1752, after the studies by Schaeffer, it was recognized as a new element.
During the 70s of the 18th century the first technical products were made of platinum (plates, wires and crucibles). These products were, of course, imperfect. They were prepared by compressing the spongy platinum under intense heat. Janetti, a jeweler from Paris (born in 1790), achieved excellence in manufacturing the products of platinum for the scientific purposes. He alloyed the native platinum and arsenic over the lime or alkali and then kilned the excess arsenic at intense roasting. A malleable metal good for further processing was produced.
In 1808 to 1809 vessels of almost 16 kg in weight were made of platinum in France and England (virtually simultaneously). These vessels were intended for the strong sulfuric acid production.
The emergence of such products as well as discovery of the element’s valuable properties made the demand for it grow, the price of platinum increased, which, in turn, stimulated new researches and searches.
In Russia platinum was first found in 1819 in the Urals, in Verkh-Isetsky district. During the washing of gold-bearing rocks white shining grains were noticed. Even the strongest acids could not dissolve those grains.
In 1823 V.V. Lyubarsky studied those grains and found that the mysterious metal was a special kind of crude platinum. The same year a royal decree followed ordering all the mining chiefs to search for platinum, separate it from gold and send it to Saint Petersburg. In 1828 Russia mined a then-unparalleled amount of platinum: 1,550 kg a year, i.e. 1.5 times more than the whole amount mined in South America from 1741 to 1825...
Before the World War I the platinum production in Russia accounted for 90% to 95% of the world production but 9/10 of the Russian platinum were exported and only few per cent were processed at two small factories.
Immediately after the October Revolution, measures have been taken to establish a strong industry of platinum. In May 1918 the Platinum Studies Institute later integrated into the Institute of General and Inorganic Chemistry of the USSR Academy of Sciences named at present after the academician N.S. Kurnakov, was established. Numerous researches concerning chemistry and technology of platinum and other precious metals have been carried out in the institute under the supervision such eminent scientists as L.A. Chugaev, N.S. Kurnakov and I.I. Chernyaev.
Palladium was discovered by William Hyde Wollaston (1803), a famous English scientist, in the part of the crude platinum soluble in the aqua regia. There is a story related to the discovery of palladium. When Wollaston produced some metal, he did not publish a report on his discovery and distributed an anonymous advertisement in London saying that the new metal, palladium, being by nature the new silver, the new precious metal, was traded in the store of Forster, a minerals dealer. Richard Chenevix, a chemist, got interested in that. He bought a sample of the metal and when he familiarized himself with its properties he assumed that the metal was made of platinum by alloying it with mercury according to the method of A.A. Musin-Pushkin, a Russian scientist. Chenevix expressed his opinion in print media. The advertisement’s anonymous author announced that he was willing to pay 20 pounds to anyone who would manage to artificially produce a new metal. Of course, neither Chenevix nor other chemists were able to do this. Sometime later Wollaston officially announced that he had discovered palladium and described how to extract it from crude platinum. At the same time he announced the discovery and properties of rhodium, another platinum-group metal. Wollaston derived the word palladium from the name of the minor planet, Pallas, discovered not long before that (in 1801) by Olbers, a German astronomer.
Rhodium was discovered in 1804 by Wollaston following the discovery of palladium. Wollaston dissolved crude platinum in aqua regia and then neutralized the excess acid by caustic soda. He distilled platinum from the neutral solution by ammonium chloride and palladium by mercuric cyanide. The filtrate treated by hydrochloric acid to eliminate the excess mercuric cyanide was boiled dry. After the treatment by alcohol the residue was in the form of dark-red powder of 2-sodium-hydrogen chloride. The metal is easily produced from the powder during roasting in the current of hydrogen. The word rhodium is derived from the Greek rose after the color of metal salts solution in the water.
IRIDIUM and OSMIUM
At the beginning of the 19th century analytical chemists from various countries got interested in crude platinum assuming that it contained new elements. As Wollaston studied the crude platinum soluble in the aqua regia, Descotille, Fourcroy and Vauquelin started studying the crude platinum part insoluble in the aqua regia. By alloying it with caustic potash they produced alloys of unknown water-insoluble metals that they could not identify. Tennant took the same path and in 1804 he managed to produce two new metals: osmium and iridium. The name iridium is derived from Greek rainbow and iridescent because the alloys of new metal (chlorides) were dyed various beautiful colors. The name osmium was given because when the alkali osmiridium alloy dissolves in water or acid there is a persistent odor similar to the throat-irritating odor of chlorine or radish (Greek - odor).
This platinum-group metal was discovered in 1844 by K.K. Klaus in Kazan when he had been analyzing the so-called works-supplied platinum residue. When he received about 15 pounds of such residue from the mint of Saint Petersburg, after extraction of some platinum-group metals from the ore Klaus alloyed the residue with saltpeter and extracted the water-soluble part (containing osmium, chromium and other metals). He exposed the water-insoluble residue to aqua regia and distilled it until dry. When Klaus treated the dry residue after distillation by boiling water and added excess potassium carbonate he separated the residue of ferric hydroxide where he found an unknown element by dark purple-red color of the residue solution in the hydrochloric acid. Klaus isolated the new metal in the form of sulfide and suggested to name it ruthenium after Russia (Latin Ruthenia means Russia).