CHAPTER IIISOURCES OF SUPPLY OF PLATINUM METALS(b) FOREIGN COUNTRIES
Platinum metals are not produced in France, but platinum is known to occur at several places. In the Department of Charaste and Deux Sevres it occurs associated with pyrite and limonite; in the Valle du Drae, Hautes Alpes, above Chatalard, platinum occurs in tetrahedrite in metamorphic limestone; at St. Arey, near La Mure (Isere), it occurs in bournonite, in dolomite and altered limestone. Platinum is found in argentiferous tetrahedrite and malachite near Presles, in Savoy[31].
As mentioned below, under Russia (p.36), France controlled the production of platinum in Russia before the war through the Compagnie Internationale du Platine, due to its extensive ownership of platinum deposits and its contracts with Russian companies.
The accompanying table gives a summary of recent imports, with countries of origin, as far as can be obtained.
Recent imports in kilograms (42·87 troy oz.) into France of crude, manufactured and scrap platinum, were as under:
Platinum has recently been discovered in Westphalia, deposits having been found in Freudenberg, Siegen, Meschede, in Siegerland, Sauerland and Westerwald. It occurs in a series of fragmental deposits, including principally slates and graywackes, the latter composed of quartz and slate, with an argillaceous cement; it is also occasionally found in the recemented fragments which are presumably derived from the basal granite formation, underlying the platinum series[46]p. 606. The beds are believed to be of marine origin, and are probably of Silurian and Devonian age. The platinum, which is present in a very finely-disseminated state, is associated with chromium, nickel, arsenic, antimony, iron, copper, lead, zinc, silver and gold, some of which appear to have been introduced by solutions at a stage subsequent to sedimentation. Krusch investigated these deposits in 1914, and is of opinion, in view of the similarity of the chemical associations with those of the Ural and British Columbian formations, that the original source of the platinum was peridotite, or other form of basic igneous rock. A number of samples, analysed by Krusch, yielded values ranging from a trace to 33·5 gm. (1 oz. troy) platinum per ton[47]. At the outbreak of war the capital necessary for exploitation had not been raised, but in 1918 it was stated that treatment works had been erected at Wenden[2].
As mentioned above, about 25 per cent. of the Russian output of platinum before the war was refined in Germany,and it is known that German capital was helping to finance the pre-war platinum operations of that country[2].
The following is a summary of imports into Germany of crude, manufactured and scrap platinum in kilograms (42·87 troy oz.) for the years 1910–13:
Up to the year 1914, Russia produced about 93 per cent. of the total world’s supply of platinum, the metal being derived from extensive deposits of alluvial sands in the Ural Mountains. The platiniferous area extends approximately 80 miles along the central part of the chain of mountains in the Government of Perm, and along the eastern slope, the principal centre of the placers being at Goroblagodat, and on the western side at Nizhni-Tagilsk.
Platinum was first discovered in the Urals in 1823, and exploitation commenced in the following year. In 1828 the Russian Government instituted platinum coinage, which consisted of 3–rouble, 6–rouble and 12–rouble pieces, the coins containing about 2 per cent. iridium. A 3–rouble piece weighed 10·31 gm., and the price paid by the Government to the producers was 16s.10d.per oz.; but owing to the subsequent rise in value of platinum, the coinage was discontinued in 1845[48]p. 606.
The platinum industry began to develop in 1869, the price at that time being under £5 per lb.[49], but from that year onwards the value, although subject to considerable fluctuations, has steadily increased. It has been estimated that since the beginning of the industry in Russia, about 6,000,000oz. of platinum have been recovered from 30,000,000 to 40,000,000 c. yd. of gravel.
As was explained in Chapter I, the official statistics of the Russian output of crude platinum are considered to be low. In the following table, the estimated and official figures of production are given for the years 1910–17:
In the official statistics the Ural mining district is divided into five principal areas. The following table shows the annual outputs by districts in recent years:
Exports of crude platinum from Russia for the years 1911–15 were as follows[15]p. 923:
The platinum industry in Russia has always been mainly in the hands of a few large firms of foreign countries. For a long time Johnson, Matthey & Co., Ltd. controlled the greater part of the trade. In 1898 the Société Anonyme de l’Industrie du Platine was established in Paris, and, by purchasing a large number of mines, and leasing others, was able to secure a large share in the control of the industry.
The refining of the crude platinum has been, and still is, almost entirely in foreign hands, all but approximately 2 per cent. of the entire output being refined abroad. In 1915 it was reported that the construction of a refinery at Ekaterinburg was completed, which was to be placed under Government control. The principal platinum-refining works were formerly those of Johnson, Matthey & Co., Ltd., of England, but early in the eighties this firm was, to a certain extent, superseded by Heraeus & Co., of Hanau, Germany. They, in turn, in 1909, were compelled to give first place to the Société Anonyme de l’Industrie du Platine, of Paris, which became the chief centre of the platinum-refining industry, a position which it held until the outbreak of war. France at that time had a monopoly of 90 per cent. of the Russian production. This foreign control had an unfavourable effect on the industry, and in 1913 the Russian Government passed a law forbidding the exportation of crude platinum. In July 1915, exportation was again permitted, subject to a 30 per cent.ad valoremexport tax, and at about the same time an order was issued forbidding the exportation of raw platinum in quantities valued above 500 roubles (£53), the price of the metal to be fixed by the State[15]p. 923. In February 1917 the Government further enacted an order prohibiting the importation of drawn and spun platinum. It was hoped by these means to encourage the establishment of domestic refineries. In 1916 the Government fixed the price at £16 10s. per oz. In March 1917 it was reported that the miners were not satisfied, and later sales were reported up to £22 per oz. of crude metal, 83 per cent. fine[50]p. 17.
According to N. Vissotzki[51], the platiniferous belt of the Urals, geologically speaking, consists of four parallel bands striking, roughly, north and south; the westernmostof these, made up of crystalline schists, forms the watershed between Europe and Asia. The next band to the east comprises olivine- and mica-gabbros, diallage-peridotites, diorites and altered syenites—all of which have been erupted from a great depth. The third band is made up of Lower Devonian sedimentary rocks, shattered and buried in places by diabasic eruptive rocks. The eastern portion of this band is formed of eruptive rocks of deep-seated origin which may be gneissose granites. The fourth, or most easterly band, is composed of ancient rocks, which have been eroded by the advancing sea of Lower Tertiary age.
The area emerged from the waves as early as the Carboniferous period; consequently the accumulation of platinum, and in some localities of gold, in the surface-deposits, were not swept away. They were concentrated later on in the alluvia—perhaps at the time of the most intense glaciation, probably in the Pleistocene.
Throughout the Urals, the primary source of the platinum is associated with the eruptive basic rocks, among which the platiniferous and auriferous dunite forms three great masses. The principal outcrops of platiniferous dunite and platinum-bearing alluvia are connected with the second of the four parallel bands mentioned above. Towards the south, the band becomes discontinuous, and finally dies out altogether. Here a few outcrops of platiniferous olivine-rock contain a small percentage of platinum, with osmiridium and other members of the group associated with it.
The two principal platinum-producing districts are in the central Urals, and are: (1) The Shuvaloff Estates, Isov district, on the River Iss, near Goroblagodat. (2) The Demidoff Estates, Nizhni-Tagilsk district, on the Martian River in the South Verkhotur district. Prior to 1879 the latter field furnished the larger part of the platinum, but since then the former has been the most productive, and now supplies about 80 per cent. of the total output. The whole of the platinum is derived from gravel deposits, which are usually auriferous, and associated with dunite.
The Isov district.—Platinum is concentrated in the channels of the Rivers Iss, Veeya and Tura. In the north of this regionit is obtained from the Sosnovki, Kytlymi, and Mala Kosva Rivers; further north again, platinum occurs with gold in the Vagran River, and in the system comprising the Rivers Lobva, Niasma, Lialia, Aktai, Emerlo and Talits, the gold here being predominant. Other sources of supply of platinum and gold in this district are on the Ivdevl River. In the south of the area, platinum deposits are worked on the tributaries of the Tagil, Salda, Imiaun and Tura Rivers[15]p. 921.
The Nizhni-Tagilsk district.—The richest placers occur in the valleys of the Visim, Martian, Sisim, Chaush and Cherna Rivers. Further south, platinum is found with gold in the gravels of the Nevian, Verkhne-Iset, Bilenibaev, Alapaev, Sysert, Kyshtym and Mias areas, and also in the Tanalyk, Sakmar and Urtazym Rivers.
Other localities of smaller importance are the Nikolae Pavdinsk and Rastes districts in the northern Urals, and the Systersk mining district.
The placers are derived from country rock, made up of serpentine gabbro, diallage and olivenite, the principal associated minerals being quartz, zircon, ilmenite, chromite, magnetite, spinel, native gold and palladium. Gold is present in the concentrate in very variable quantities, and sometimes contains silver, but the latter generally occurs in combination with palladium. The crude platinum usually includes some iridium, rhodium, ruthenium and iron.
The basic igneous rocks, from which the platinum is derived, are exposed in the form of discontinuous elliptical outcrops near the summits of the Urals, particularly on the western side of the mountains. These outcrops attain larger dimensions in the northern and central Urals than further south. The process of concentration of platinum in the gravels has clearly extended over a very long period of time, and it is probable that the richer gravels have been reconcentrated, perhaps several times[52]p. 299. Platinum nuggets are rarely found, but three of large size were discovered in the Nizhni-Tagilsk district, their weights respectively being 25½ lb., 21 lb., and 11½ lb.
Duparc, in a brief description of the geology of the deposits, states that they are essentially of magmatic origin. Thestructure of the rock is in the nature of concentric bandings; the felspathic rocks at the outer edge gradually grade into the intermediate stage of pyroxenes, until the central dunite is reached, composed of olivine and chromite. The richness of the gravels is in proportion to the size of the dunite deposits, and to the extent of erosion of these rocks. According to Duparc, platinum ore derived from a pyroxenite source usually contains high percentages of platinum and palladium, but low percentages of osmium and iron. The same writer estimated in 1916 that the reserves were sufficient for about twelve years, provided that the same methods of working and rate of extraction were employed during that period[53].
The amount of the platinum in the wash is very variable. The average yield was formerly over ½ oz. per c. yd., but latterly, owing to the gradual exhaustion of the richer deposits, the average returns have not exceeded from 2 to 3 dwt. per c. yd. The crude metal assays about 83 per cent. platinum, from 5 to 7 per cent. osmium and iridium, with small amounts of ruthenium, palladium, and gold, and about 10 per cent. impurities, mostly iron and copper[54]. The thickness of the pay gravels varies from 3 to 6 ft., and about 4 ft. may be taken as the average width, the overburden running from a few to over 60 ft. The extent of the productive area is about 170 sq. miles, and from 15,000 to 20,000 miners were employed before the war[4]p. 558. It has been noticed that the platinum deposits are characterized by their uniformity, of course not being so sinuous in direction as gold deposits.
In former times mining was entirely carried on by primitive methods with hand labour, but the utilization of dredges has steadily increased, since their introduction in 1900. In 1909, 13 per cent. of the total production was obtained by dredging, and in 1914 this percentage rose to one-third of the total output. The season during which dredges may be employed extends on the average from the middle of April to the middle of October. In the South Verkhotur and Perm areas dredges have been used in the large enterprises; but at the small mines the working is very primitive, and carried on largely with the help ofstarateli, or tributers. In 1914 amodern 7½ c. ft. dredge was installed on the Nikolaie-Pavdinsk Estate.
In mines where dredging is not in use, the gravels are mined by open cuts, or, if the overburden is thick, shafts are employed. The former method is much preferred, both on account of its relative cheapness, and also because it is possible to obtain a better clean-up of the bedrock.
The usual types of stationary plant in use include thebotchka, or conical revolving screen; thetchaska, or puddling machine, with a bottom of perforated iron plates; and theboronka, or conical screen, on which the stones and clay are turned over by a double rake[55]. The gold is removed by amalgamation with mercury in wood, iron or porcelain bowls. Special methods are in use in certain parts of Russia for working the deposits during the winter. The workings are allowed to freeze, and the frozen ground is mined after being partially thawed by means of wood fires. The method is simple, but care must be taken to ensure that the thawing does not proceed too far, otherwise the ground collapses, and the workings become flooded. The method is suitable for depths to 30 ft., and in localities where the snowfall is comparatively slight.
Latest reports from Russia indicate that no dredges are now working there, the platinum being produced by hand methods only.
Some interesting experiments were recently carried out by V. N. Chorzhevski in the Nizhni-Tagilsk district, with a view to testing the commercial possibility of mining platinumin situ. The metal here occurs, in association with chrome iron ore, in dunite rock, which in this region extends over an area of 11½ sq. miles. The platinum appears to be present in quantities directly proportional to the amount of chromite in the rock. The dunite is first ground under runners; the chromite slack is separated from it; and after this has undergone a second grinding, the metal is separated by washing[56]. An experimental test, carried out in March 1917, is stated to have produced over 200 oz. platinum from 9,720 lb. chromite slack. Another experiment with 3,600 lb. of grey slack, “or fines,” consisting chiefly of undecomposed dunite obtained from the dredges, is reported to have yielded ⅓ oz. of platinum.
Lapland.—Platinum occurs associated with chromite and diamonds, in alluvial deposits on the Ivalo River. It is believed to be derived from serpentine rock, of which the neighbouring country is largely composed[4]p. 556.
Finland.—Platinum has been found in the south in a lode-formation containing quartz, siderite, calcite and dolomite. Gold and carbonate of copper are also present in small quantities.[4]p. 557.
In a dispatch to the Great Powers on February 26, 1920, the Soviet Government promised to withdraw the decree annulling Russia’s foreign debt, to pay arrears of interest, and giving as a guarantee to an Anglo-American syndicate certain important platinum and silver-mining concessions, in return for which the abandonment of intervention in Russia’s internal affairs was demanded. To be used in payment of foreign purchases, the Government was about to issue “platinum” credit notes of 50, 100, 500, and 5,000 roubles, the issue to be limited to 65,000,000 roubles, and backed by platinum reserves of 37,500,000 roubles. The Government would be ready to convert the platinum reserves into coin if required[57].
Promising deposits of platinum have recently been reported at Ronda, in the province of Malaga. Domingo de Orueta, a Government geologist, having noticed the similarity of the geology of this district to that of the platiniferous deposits of the Urals, proceeded, a few years ago, to explore the area systematically, and was soon rewarded, in the discovery of the metal. The deposits, which are alluvial, extend along the Verde and Guadaiza rivers, and are derived from serpentine and peridotite rocks, the latter composed principally of rhombic pyroxene, with some spinel and some dunite. Chromite occurs in association with the platinum. The pay gravels contain about 8 gr. platinum per ton, and are stated to have an average thickness of 5 ft., the depth of overburden in the Guadaiza area, where apparently the richer gravels are found, being about 33 ft., as compared with 49 ft. in the Verde locality[10]p. 547. The Spanish Government have taken over the exploitation of these deposits, and no public prospecting, without Government permission, is allowed.
Platinum is known to exist in a number of other localities in Spain, especially in the northern districts; but so far as is known, it occurs in very small quantities of no commercial importance. The metal has been recognized in the following rivers: Minho, Luna, Sil, Orbigo, Gallego, Cinca Darro and Lower Jenil, where it occurs in the concentrate sands, accompanied by magnetite, ilmenite, zircon and, frequently, gold[58].
Platinum, in association with gold, is reported to occur in the district of Batum and Sasun, on the Charokh River[46]p. 610.
Platinum was discovered in south-eastern Borneo in 1831, in the gravels of Gunung Lawack, but for a long time the natives were ignorant of its value. In recent years it has been obtained on a small scale as a by-product in the process of gold-washing, carried on in the province of Tanah-Laut, in the south-eastern extremity of the island[59]. The deposits occur in streams, which rise in the Bobaris Mountains, where the country rocks are composed of schists and gneisses, intruded by serpentine gabbro and diorite dykes[52]p. 298. Platinum has, however, not yet been locatedin situ. In addition to gold, the platinum is associated with osmiridium in the gravels, the two former being frequently found intimately intergrown. The platinum content of the native metal has been found by a number of analyses to vary from about 57 to 83 per cent., and that of osmiridium from 0·18 to 10·07 per cent.[60].
The rare minerallaurite, a sulphide of ruthenium and osmium, was discovered in these deposits.
According to L. Hundeshagen[61], the platinum occurring in the diamond placers of western and south-eastern Borneois in the form of thin scales, ranging from 0·1 to 1·0 mm. in length. These platinum scales contain from 3·8 to 4·5 per cent. of copper, evidently as an alloy.
In the Uryanchai district of Mongolia, situated on the Russian border, deposits of auriferous gravels have been worked on a fairly extensive scale for some time past. It was announced a few years ago that platinum and iridium had been found in appreciable quantities, associated with the gold, some large platinum nuggets being obtained from this region in 1911. Although no attempt at commercial development has yet been made, the prospects of profitable extraction appear to be hopeful. Extensive outcrops of olivine rocks have been noticed in the vicinity, and the nature of the occurrence is stated to bear some resemblance to that of the platiniferous fields of the southern Urals[8]p. 107.
Platinum occurs in the Yubari-garva, Pechau and other rivers in the province of Hokkaido. It is also found in Nishi-Mikawa, province of Sado. In the former locality gold and iridosmine are associated with the platinum, and in the latter gold and iron sands are present[62]. In no case has the metal been traced to its parent source. In the Hokkaido deposits the average quantity of platinum present is only 2 or 3 per cent. of the iridosmine content. It is possible that further exploration in these areas will reveal occurrences of greater importance[9]p. 597.
Platinum is obtained at Sipongi, where it occurs with wollastonite and grossularite in limestones and schists, near intrusions of granodiorite and augite diorite. Gold is also present.
L. Hundeshagen[61]is of opinion that the present ore deposit was originally a layer, or a big lens, of limestone embeddedin the old schists, which has, by apophyses of granite, been altered into garnet and wollastonite, being at the same time, or very soon afterwards, mineralized by hot solutions carrying copper, gold, platinum, etc. A sample of slightly decomposed wollastonite with no copper, or only minute traces of that metal, proved to be richest in platinum, the assay showing 6 gm. of platinum per 1,000 kg., while samples with 2 to 10 per cent. of bornite and malachite contained only traces of platinum; and none could be detected in auriferous garnet, poor in wollastonite. About 10 to 25 metres from the outcrop the concentrated river sand shows small particles of whitish crystalline gold and rounded grains of white platinum, the latter varying from 0·1 to 0·3 mm. in size.
In the Katanga district, platinum and palladium have been reported to occur in certain alluvial gravels, accompanied by gold and silver. One sample from this locality is stated to have yielded the following amounts per metric ton: 3·4 gr. platinum, 12·3 gr. gold, 8·3 gr. silver. It has also been locatedin situin sandstones containing gold.
Platinum is produced on a small scale as a by-product in alluvial gold mining on the Vatana River, near the village of Ambia, in the Vatomandry district. Traces of the metal have also been found in auriferous gravels in the regions of Fenerive, Marolambo, and Vandrozo, over an area extending along the eastern side of the island for a length of about 450 miles. The platinum is apparently derived from the decomposition of pegmatite. It is rarely found pure, being usually coated with iron oxide, and strongly magnetic, a property which is utilized in the process of separation from the gold[63].
NORTH AMERICA
Platinum has been shown to exist in the states of Guerrero and Hidalgo in deposits of ferrous clays, which are of undoubted sedimentary origin, and are apparently laterites. The metal exists in a very finely disseminated state, invisible to the naked eye[64].
At the beginning of the war there was a considerable shortage of platinum in the country, caused partly by the falling-off of the imports, and in part owing to the increased demand in connexion with munition manufacture.
California is the principal producer of crude platinum, and in 1917 this State supplied 460 oz. out of the total output of 605 oz.; with the exception of a few ounces from the State of Washington, Alaska and Oregon provided the balance.
A considerable quantity of foreign crude and manufactured platinum is imported annually, as shown in the following tables: