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LOOKING See also:EAST mine in the See also:Transvaal, about 300 M. to the east of See also:Kimberley. This, was discovered in 1902 and occupies an See also:area of about 75 acres. In 1906 it was being worked as a shallow open mine; but the description of the Kimberley methods given above is applicable to the washing plant at that See also:time being introduced into the Premier mine upona very large See also:scale. Comparatively few of the pipes which have been discovered are at all See also:rich in diamonds, and many are quite barren; some are filled with " hard See also:blue " which even if diamantiferous may be too expensive to See also:work. The most competent S. See also:African geologists believe all these remark-able pipes to be connected with volcanic outbursts which occurred over the whole of S. See also:Africa during the Cretaceous See also:period (after the deposition of the Stormberg beds), and drilled these enormous craters through all the later formations. With the true pipes are associated dykes and fissures also filled with diamantiferous blue ground. It is only in the more northerly See also:part of 'the See also:country that the pipes are filled with blue ground (or " kimberlite "), and that they are diamantiferous; but over a See also:great part of Cape See also:Colony have been discovered what are probably similar pipes filled with agglomerates, breccias and tuffs, and some with basic lavas; one, in particular, in the Riversdale See also:Division near the See also:southern See also:coast, being occupied by a melilite-See also:basalt. It is quite clear that the occurrence of the See also:diamond in the S. African pipes is quite different from the occurrences in alluvial deposits which have been described above. The question of the origin of the diamond in S. Africa and elsewhere is discussed below. The See also:River Diggings on the See also:Vaal river are still worked upon a small scale, but the See also:production from this source is so limited that they are of little See also:account in comparison with the mines in the blue ground. The stones, however, are See also:good; since they differ somewhat from the Kimberley crystals it is probable that they were not derived from the See also:present pipes. Another S. African locality must be mentioned; considerable finds were reported in 1905 and 1906 from gravels at Somabula near Gwelo in See also:Rhodesia where the diamond is associated with See also:chrysoberyl, See also:corundum (both See also:sapphire and See also:ruby), See also:topaz, See also:garnet, See also:ilmenite, See also:staurolite, See also:rutile, with pebbles of See also:quartz, See also:granite, Zr From See also:Gardner See also:Williams's Diamond Mines of See also:South Africa. FIG. 8. e wo00 SCALE 000 200 600 400 600 I-. See also:chlorite-schist, &c. Diamond has also been reported from kimberlite " pipes " in Rhodesia. Other Localities.—In addition to the South See also:American localities mentioned above, small diamonds have also been See also:mined since their See also:discovery in 1890 on the river Mazaruni in See also:British See also:Guiana, and finc{s have been reported in the See also:gold washings of Dutch Guiana. See also:Borneo has possessed a diamond See also:industry since the See also:island was first settled by the See also:Malays; the references in the See also:works of See also:Garcia de See also:Orta, Linschoten, De See also:Boot, De Laet and others, to Malacca as a locality relate to Borneo. The large Borneo See also: See also:Siberia has yielded isolated diamonds from the gold washings of See also:Yenisei. In North See also:America a few small stones have been found in alluvial deposits, mostly auriferous, in See also:Georgia, N. and S. Carolina, See also:Kentucky, See also:Virginia, See also:Tennessee, See also:Wisconsin, See also:California, See also:Oregon and See also:Indiana. A crystal weighing 231 carats was found in Virginia in 1855, and one of 214 carats in Wisconsin in 1886. In 1906 a number of small diamonds were discovered in an altered See also:peridotite some-what resembling the S. African blue ground, at See also:Murfreesboro, See also:Pike See also:county, See also:Arkansas. Considerable See also:interest attaches to the diamonds found in Wisconsin, See also:Michigan and See also:Ohio near the Great Lakes, for they are here found in the terminal moraines of the great glacial See also:sheet which is supposed to have spread southwards from the region of See also:Hudson See also:Bay; several of the See also:drift minerals of the diamantiferous region of Indiana have been identified as probably of See also:Canadian origin; no diamonds have however yet been found in the intervening country of See also:Ontario. A See also:rock similar to the blue ground of Kimberley has been found in the states of Kentucky and New See also:York. The occurrence of diamond in meteorites is described below. Origin of the Diamond in Nature.—It appears from the foregoing account that at most localities the diamond is found in alluvial de-posits probably far from the See also:place where it originated. The minerals associated with it do not afford much See also:clue to the See also:original conditions; they are mostly heavy minerals derived from the neighbouring rocks, in which the diamond itself has not been observed. Among the commonest associates of the diamond are quartz, topaz, See also:tourmaline, rutile, See also:zircon, See also:magnetite, garnet, See also:spinel and other minerals which are See also:common See also:accessory constituents of granite, See also:gneiss and the crystalline See also:schists. Gold (also platinum) is a not infrequent See also:associate, but this may only mean that the sands in which the diamond is found have been searched because they were known to be auriferous; also that both gold and diamond are among the most durable of minerals and may have survived from See also:ancient rocks of which other traces have been lost. The localities at which the diamond has been supposed to occur in its original See also:matrix are the following:—at Wajra Karur, in the See also:Cuddapah See also:district, See also:India, M. Chaper found diamond with corundum in a decomposed red See also:pegmatite vein in gneiss. At Sao Joao da Chapada, in See also:Minas Geraes, diamonds occur in a See also:clay interstratifiect with the See also:itacolumite, and are accompanied by See also:sharp crystals of rutile and See also:haematite in the neighbourhood of decomposed quartz See also:veins which intersect the itacolumite. It has been suggested that these three minerals were originally formed in the quartz veins. In both these occurrences the See also:evidence is certainly not sufficient to establish the presence of See also:ari original matrix, At Inverell in New South Wales a diamond (1906) has been found embedded in a See also:hornblende See also:diabase which is described as a dyke intersecting the granite. Finally there is the remarkable occurrence in the blue ground of the African pipes. There has been much controversy concerning the nature and origin of the blue ground itself ; and even granted that (as is generally believed) the blue ground is a much serpentinized volcanic breccia consisting originally of an See also:olivine-See also:bronzite-See also:biotite rock (the so-called kimberlite), it contains so many rounded and angular fragments of various rocks and minerals that it is difficult to say which of them may have belonged to the original rock, and whether any were formed in situ, or were brought up from below as inclusions. Carvill See also:Lewis believed the blue ground to be true eruptive rock, and the See also:carbon to have been derived from the bituminous shales of which it contains fragments. The Kimberley shales, which are penetrated by the De Beers See also:group of pipes, were, however, certainly not the source of the carbon at the Premier (Transvaal) mine, for at this locality the shales do not exist. The view that the diamond may have crystallized out from See also:solution in its present matrix receives some support from the experiments of W. Luzi, who found that it can be corroded by the solvent See also:action of fused blue ground; from the experiments of J. Friedlander, who obtained diamond by dissolving See also:graphite in fused olivine; and still more from the experiments of R. von Hasslinger and J. See also:Wolff, who have obtained it by dissolving graphite in a fused mixture of silicates having approximately the See also:composition of the blue ground. E. See also:Cohen, who regarded the pipes as of the nature df a mud See also:volcano, and the blue ground as a kimberlite breccia altered by hydrothermal action, thought that the diamond and accompanying minerals had been brought up from deep-seated crystalline schists. Other authors have sought the origin of the diamond in the action of the hydrated magnesian silicates on See also:hydrocarbons derived from bituminous schists, or in the decomposition of metallic carbides.
Of great scientific interest in this connexion is the discovery of small diamonds in certain meteorites, both stones and irons; for example, in the stone which See also:fell at Novo-Urei in See also:Penza, See also:Russia, in 1886, in a stone found at Carcote in See also:Chile, and in the See also:iron found at Cation Diablo in See also:Arizona. Graphitic carbon in cubic See also:form (cliftonite) has also been found in certain meteoric " irons," for example in those from Magura in Szepes county, See also:Hungary, and Youndegin near York in Western Australia. The latter is now generally believed to be altered diamond. The fact that H. See also:Moissan has produced the diamond artificially, by allowing dissolved carbon to crystallize out at a hign temperature and pressure from molten iron, coupled with the occurrence in meteoric iron, has led See also:Sir See also: The meteoric iron of Arizona, some of which contains diamond, is actually found in and about a huge See also:crater which is supposed by some to have been formed by an immense See also:meteorite penetrating the See also:earth's crust. It is, at any See also:rate, established that carbon can crystallize as diamond from solution in iron, and other metals; and it seems that high temperature and pressure and the See also:absence of oxidizing agents are necessary conditions. The presence of See also:sulphur, See also:nickel, &c., in the iron appears to favour the production of the diamond. On the other See also:hand, the occurrence in meteoric stones, and the experiments mentioned above, show that the diamond may also crystallize from a basic magma, capable of yielding some of the metallic oxides and ferro-magnesian silicates; a magma, therefore, which is not devoid of See also:oxygen. This is still more forcibly suggested by the remarkable See also:eclogite See also:boulder found in the blue ground of the See also:Newlands mine, not far from the Vaal river, and described by T. G. See also:Bonney. The boulder is a crystalline rock consisting of See also:pyroxene (chrome-See also:diopside), garnet, and a little olivine, and is studded with diamond crystals; a portion of it is preserved in the British Museum (Natural See also:History). In another eclogite boulder, diamond was found partly embedded in See also:pyrope. Similar boulders have also been found in the blue ground elsewhere. Specimens of pyrope with attached or embedded diamond had previously been found in the blue ground of the De Beers mines. In the Newlands boulder the diamonds have the See also:appearance of being an original constituent of the eclogite. It seems therefore that a holocrystalline pyroxene-garnet rock may be one source of the diamond found in blue ground. On the other hand many tons of the somewhat similar eclogite in the De Beers mine have been crushed and have not yielded diamond. Further, the ilmenite, which is the most See also:character-See also:late associate of the diamond in blue ground, and other of the accompanying minerals, may have come from basic rocks of a different nature. The Inverell occurrence may prove to be another example of diamond crystallized from a basic rock. In both occurrences, however, there is still the possibility that the eclogite or the basalt is not the original matrix, but may have caught up the already formed diamond from some other matrix. Some regard the eclogite boulders as derived from deep-seated crystalline rocks, others as concretions in the blue ground. None of the inclusions in the diamond gives any clue to its origin; diamond itself has been found as an inclusion, as have also See also:black specks of some carbonaceous materials. Other black specks have been identified as haematite and ilmenite; gold has also been found; other included minerals recorded are rutile, topaz, quartz, See also:pyrites, See also:apophyllite, and See also:green scales of chlorite (?). Some of these are of very doubtful See also:identification; others (e.g. apophyllite and chlorite) may have been introduced along cracks. Some of the fibrous inclusions were identified by H. R. Goppert as See also:vegetable structures and were supposed to point to an organic origin, but this view is no longer held. Liquid inclusions, some of which are certainly carbon dioxide, have also been observed. Finally, then, both experiment and the natural occurrence in rocks and meteorites suggest that diamond may crystallize not only from iron but also from a basic silicate magma, possibly from various rocks consisting of basic silicates. The blue ground of. S. Africa may be the result of the serpentinization of several such rocks, and although now both brecciated and serpentinized some of these may have been the original matrix. A circumstance often mentioned in support of this view is the fact that the diamonds in one pipe generally differ somewhat in character from those of another, even though they be near neighbours. History.—All the famous diamonds of antiquity must have been See also:Indian stones. The first author who described the Indian mines at all fully was the Portuguese, Garcia de Orta (1565), who was physician to the See also:viceroy of See also:Goa. Before that time there• were only legendary accounts like that of Sindbad's " Valley of the Diamonds," or the See also:tale of the stones found in the brains of serpents. V. See also:Ball thinks that the former See also:legend originated in the Indian practice of sacrificing See also:cattle to the evil See also:spirits when a new mine is opened; birds of See also:prey would naturally carry off the flesh, and might give rise to the tale of the eagles carrying diamonds adhering to the See also:meat. The following are some of the most famous diamonds of the See also:world: A large stone found in the See also:Golconda mines and said to have weighed 787 carats in the rough, before being cut by a Venetian See also:lapidary, was seen in the See also:treasury of See also:Aurangzeb in 1665 by See also:Tavernier, who estimated its weight after cutting as 280 (?) carats, and described it as a rounded lose-cut-stone, tall on one See also:side. The name Great See also:Mogul has been frequently applied to this stone. Tavernier states that it was the famous stone given to Shah Jahan by the emir Jumla. The Orloff, stolen by a See also:French soldier from the See also:eye of an idol in a Brahmin See also:temple, stolen again from him by a See also:ship's See also:captain, was bought by See also:Prince Orloff for £90,000, and given to the empress Catharine II. It weighs 1944 carats, is of a somewhat yellow tinge, and is among the See also:Russian See also:crown jewels. The Koh-i-nor, which was in 1739 in the See also:possession of See also:Nadir Shah, the See also:Persian conqueror, and in 1813 in that of the See also:raja of See also:Lahore, passed into the hands of the East India See also:Company and was by them presented to See also:Queen Victoria in 1850. It then weighed 1861-6- carats, but was recut in See also:London by See also:Amsterdam workmen, and now weighs ro61G- carats. There has been much discussion concerning the possibility of this stone and the Orloff being both fragments of the Great Mogul. The Mogul See also:Baber in his See also:memoirs (1526) relates how in his See also:conquest of India he captured at See also:Agra the great stone weighing 8 mishkals, or 320 ratis, which may be See also:equivalent to about 187 carats. The Koh-i-nor has been identified by some authors with this stone and by others with the stone seen by Tavernier. Tavernier, however, subsequently described and sketched the diamond which he saw as shaped like a bisected See also:egg, quite different therefore from the Koh-i-nor. Nevil See also:Story See also:Maskelyne has shown See also:reason for believing that the stone which Tavernier saw was really the Koh-i-nor and that it is identical with the great diamond of Baber; and that the 28o carats of Tavernier is a misinterpretation on his part of the Indian weights. He suggests that the other and larger diamond of antiquity which was given to Shah Jahan may be one which is now in the treasury of See also:Teheran, and that this is the true Great Mogul which was confused by Tavernier with the one he saw. (See Ball, Appendix I. to Tavernier's Travels (1889); and Maskelyne, Nature, 1891, 44, p. 555.).
The See also:Regent or See also:Pitt diamond is a magnificent stone found in either India or Borneo; it weighed 410 carats and was bought for £20,400 by Pitt, the See also:governor of See also:Madras; it was subsequently, in 1717, bought for £80,000 (or, according to some authorities, £135,000) by the See also:duke of See also: The See also: Many large stones have been found in South Africa; some are yellow but some are as colourless as the best Indian or Brazilian stones. The most famous are the following:—the Star of South Africa, or See also:Dudley, mentioned above, 831 carats rough, 461 carats cut. The See also: This extraordinary diamond weighed 302s1 carats (111b) and was clear and water white; the largest of its surfaces appeared to be a cleavage See also:plane, so that it might be only a portion of a much larger stone. It was known as the See also:Cullinan Diamond. This stone was See also:purchased by the Transvaal See also:government in 1907 and presented to King See also:Edward VII. It was sent to Amsterdam to be cut, and in 1908 was divided into nine large stones and a number of small brilliants. The four largest stones weigh 5162 carats, 3093 carats, 92 carats and 62 carats respectively. Of these the first and second are the largest brilliants in existence. All the stones are flawless and of the finest quality. and See also:Precious Metals (1883) ; M. E. Boutan, Le Diamant (1886) ; S. M. Burnham, Precious Stones in Nature, See also:Art and Literature (1887) ; P. See also:Groth, Grundriss der Edetsteinkunde (1887); A. Liversidge, The Minerals of New South Wales (1888) ; Tavernier's Travels in India, translated by V. Ball (1889); E. W. Streeter, The Great Diamonds of the World (1896); H. C. Lewis, The See also:Genesis and Matrix of the Diamond (1897) ; L. de Launay, See also:Les Diamants du Cap (1897) ; C. Hintze, Handbuch der Mineralogie (1898); E. W. Streeter, Precious Stones and Gems (6th ed., 1898) ; See also:Dana, See also:System of See also:Mineralogy (1899) ; Kunz and others, The Production of Precious Stones (in See also:annual, Mineral Resources of the See also:United States) ; M. See also:Bauer, Precious Stones (trans. L. J. See also:Spencer, .1904) ; A. W. See also:Rogers, An Introduction to the See also:Geology of Cape Colony (1905); Gardner F. Williams, The Diamond Mines of South Africa (revised edition, 1906); See also:George F. Kunz, " Diamonds, a study of their occurrence in the United States, with descriptions and comparisons of those from all known localities" (U.S. Geol. Survey, 1909) ; P. A. See also:Wagner, See also:Die Diamantfuhrenden Gesteine Sudafrikas (1909). Among papers in scientific See also:periodicals may be mentioned articles by See also:Adler, Ball, Baumhauer, See also:Beck, Bonney, See also:Brewster, Chaper, Cohen, Crookes, See also:Daubree, See also:Derby, See also:Des Cloizeaux, Doelter, Dunn, See also:Flight, See also:Friedel, Gorceix, Gtirich, Goeppert, Harger, Hudleston, Hussak, Jannettaz, Jeremejew, de Launay, Lewis, Maskelyne, See also:Meunier, Moissan, Molengraaff, Moulle, Rose, Sadebeck, Scheibe, Stelzner, See also:Stow. See generally Hintze's Handbuch der Mineralogie. (H. A. Additional information and CommentsThere are no comments yet for this article.
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