Page:Encyclopædia Britannica, Ninth Edition, v. 10.djvu/768

Rh 744 bearing quartz veins are also common over a large part of California, notably in Grass Valley (vol. iv. p. 702), in strata. that are supposed to be of Triassic age, the associated minerals being iron and arsenical pyrites, galena, &c. In Calaveras county, tellurium ores like that of Tran- sylvania are characteristic of the gold veins. In the aljaeent States of Nevada and Colorado, gold is so intimately associated with silver ores that it is for the ruost part only obtained from the ultimate process of reﬁning the reduced silver. The same remark applies to the most of the mines of Mexico, and on the south-west coast of .rnerica, in Peru, Bolivia, and Chili. See SILVER. Very rich gold quartz has been brought from Carabaya on Lake Titieaea; and recently considerable deposits both alluvial and in veins have been opened at Caratal in Vene~ zucla an-.1 at St Elie in French Guiana, which are interesting as proving the actual existence of Raleigh's Eldorado. In Brazil the principal gold mines are upon veins in clay slate, and a peculiar class of rocks known as Jaeotinga or Itabirite, and which are mixtures of quartz, chlorite, and specular iron ore, the latter often occurring in large mirror- like crystals several inches across. The gold occurs almost entirely in pyritic minerals, being most abundant in ordinary iron pyrites, and less so in magnetic and arsenical pyrites, free gold being rarely seen. See BRAZIL, vol. iv. p. 224. In Africa. the chief gold-bearing localities are on the west coast gold dust derived from alluvial washings forming an article of export from many of the trading stations along the Guinea coast. Latterly, alluvial deposits have been worked in the mountains of Transvaal, in the Leydenburg district ('2-3° S. lat., 31° E. long.), producing coarse nuggetty gold in masses up to 11 lb weight, and in a few cases gold- bearing quartz has been found in veins in talcose schist and quartzite, closely associated with eruptive masses of diorite. The age of these rocks is considered by Dunn‘ to be Silurian or Devonian, and the observed phenomena to be similar to those generally observed in Australia. The upper valley of the Nile produces a little gold in Abyssinia and Nubia, the latter being the land of gold of the old Egyptians. Very extensive ancient mines have been de- scribed by Linant Bey in the district known as Attaki or All-aki on the llezl Sea, situated about 120 miles back from llas Elba, the headland midway between Bereniee and Sauwakin. These are probably the same mines that were described by Diodorus Sieulus, and one of the oldest topographical documents known, a map or itinerary of the route to them from the Nile, is preserved at Turin. In the reign of Setee I., of the 19th dynasty, wells were opened along this route, in order that the mines, that were then of very great antiquity, might be reopened? Similar ancient gold mines have recently been discovered by Burton in the land of Midian, on the east coast of the Gulf of Akaba. The gold districts of Australia cover a very considerable area, extending from the east side of the continent for about 20° of latitude (lS° to 38° S.), the more important deposits being those of Victoria in the south. The principal districts are in Vietoria,——Ballarat, Castlemaine, and Sandhurst, lying west and north from Melbourne, and Beechworth near the Murray river to the north-east. In New South Wales the gold fields are scattered over the entire length of the colony from north to south, the more important districts lying between the 32:1 and 36th parallels of S. lat. on the western side of the Australian cordillera, on the upper tributaries of the Macquarie and Laclrlan rivers, the centre being about the town of Batlrurst. This is known as the western district. Another group, known as ‘ Qurtrlerly Jam-nrtl of the (-'rulogr'cuI Sucit:(_1/, xxxiii. p. 882. 9 Mariette Bey, Ilisloirc Ancicnne (l'Ii'r/3/pt, 1867, p. 96. The oldest notice of the mines goes back to the 12th dynasty. I G O L D the northern district, is on the eastern side of the mountains near the Queensland boundary, in 29° S., 1'iOCl{)' lliver being the principal locality; while the southern district includes Braidwood, Adelaide, Turrrbarunrba, and other localities near the Murray river. In Queensland the chief localities are, cormnerrcing on the south, Gynrpie and Kilkevan near Mary- borouglr, 26’ S. l-.rt.; a group cxteruling about 50 miles north and south of llockhanrpton, in 24° 30' S. l-.rt., all near the coast; Eastern Iliver, Hurley, and Peak llowns, about 300 miles inland on the 23d parallel; and Glonrcnny and Gilbert on a stream running into the Gulf of (‘arpentaria, besides numerous others. In all those localities two principal kinds of deposits are observed, namely, auriferous quartz veins traversing slates of Silurian and Devonian age, which are in intimate relation with masses of diorite and other eruptive rocks; and gold-bearing drifts of Miocene or even newer Tertiary date, derived from the degradation of the older strata. According to Daintree,3 no aurifcrous vein of any kind has been found in any Secondary or Tertiary strata, or in the igneous rocks erupted through any such newer formations; and as a result of his experience the sarrrc observer gives the following as the modes of occurrence of gold in Australia :——(l) In pyritic diorites and felstones in Queensland, and their alluvial drifts; (2) in pyritic granites in New South Vales ; (3) in drifts from auriferous serpen- tine in Queensland, also in the two northern colonies, (4) in more or less regular veins with quartz and calcspar in the preceding rocks; (5) in quartz and other veins in Devonian and Upper Silurian strata in proximity to similar igneous rocks, which is the general character of the Victoria quartz veins; (6) in veins of metamorphic rocks of unknown age in Queensland; and (7) in quartz veins in Lower Silurian strata, without any apparent connexion with igneous masses. The latter occur only in Victoria, and are of comparatively nrinor importance. In the northern territory of South Australia, alluvial gold mining has re- cently been developed to a considerable extent in the neigh- bourhood of Port Darwin in the Gulf of Carpentaria, the export being from 2000 to 3000 oz. monthly. Statistics. —Therc are no means of stating exactly the total gold produce of the world for any particular year, as in many of the larger producing countries no systcrrratic returns are obtained, and in others where such returns are collected their publication is often delayed for a considerable time. The following ﬁgures, mostly derived frorn a recent statistical work, A. Soctbcer, Edclmctull-I’ru¢1ul'lion, 1879. with some additions from late oflicial sources, will give some idea of the relative irnpo1'tance of the different countries. Previous to 1937 the first place was held by Russia, and the estimated average annual yield from all sources was, in the decennial period 1841-50, 1,760,500 ounces. The contributions of the difli.-r'errt countries are as follows 2-- OZ. OZ. OZ. l'nitcd States .... ..1876, 2,050,000‘ llussia .............. ..1876, 1,072,020 1877, 1,281.26‘) New South Valcs..1S76, 126,789 1877, 97,582 Victoria . .......... ..1876, 963,760 1877, 809,653 1878, 758,039 Queensland ....... ..1876, 410,330 1877, 468,418 8 1] 4 New Zr-ala11d.......1876, 322,016 1877, 371,685 1 78, 3 . 39 Venezuela... ...... .. 1873, 150.000 New Granada .... ..1876, 112,500 Africa . . . . . . . . . . . . . ..1875, 110,100 Mexico ............. ..1875, 65,950 Bolivia ............. ..1875, 64,300 Austria-Il1rngary...1876, 61,214 Brazil .............. ..1875, 55,300 Japan ............... ..1876, 21,660 Chili ................ ..1876, 12,860 Nova Scotia...... . 1876, 12,039 Perri ................ ..1876, 11,570 3 Quarterly Journal of the Gcolo_q1'cal Society, vol. xxxiv. p. 435. 4 The two principal mines, on the Cornstock lode, the Corrsolidaterl Virginia and California, produced, apart frurn silver, gold of the value in United States currency as follows: — 1976. 1877. 1878. Consolidated 'irginia...$7.:;7R.l-1.". 36,270,000 2,770,000 Culrfornsa ................ .. 6 645.641 11.3-5'6,74-'3 -5,-';5:l,4lI0