until the year 1892, when it began to increase rapidly, but not to its former level, the values for 1900 and 1905 being £3,142,000 and £3,138,000. There has been an important increase in Queensland, which advanced from £1,696,000 in 1876 to £2,843,000 in 1900, and subsequently declined to £2,489,000 in 1905. There has been no increase, and, indeed, no large fluctuation until quite recently in the output of New Zealand, which averaged £1,054,000 per annum from 1876 to 1898, but the production of the two years 1900 and 1905 rose to £1,425,459 and £2,070,407 respectively. By far the most important addition to the Australasian product has come from West Australia, which began its production in 1887—about the time of the inception of mining at Witwatersrand (“the Rand”) in South Africa—and by continuous increase, which assumed large proportions towards the close of the 19th century, was £6,426,000 in 1899, £6,179,000 in 1900, and £8,212,000 in 1905. The total Australasian production in 1908 was valued at £14,708,000.
Undoubtedly the greatest of the gold discoveries made in the latter half of the 19th century was that of the Witwatersrand district in the Transvaal. By reason of its unusual geological character and great economic importance this district deserves a more extended description. The gold occurs in conglomerate beds, locally known as “banket.” There are several series of parallel beds, interstratified with quartzite and schist, the most important being the “main reef” series. The gold in this conglomerate reef is partly of detrital origin and partly of the genetic character of ordinary vein-gold. The formation is noted for its regularity as regards both the thickness and the gold-tenor of the ore-bearing reefs, in which respect it is unparalleled in the geology of the auriferous formations. The gold carries, on an average, £2 per ton, and is worked by ordinary methods of gold-mining, stamp-milling and cyaniding. In 1899, 5762 stamps were in operation, crushing 7,331,446 tons of ore, and yielding £15,134,000, equivalent to 25.5% of the world’s production. Of this, 80% came from within 12 m. of Johannesburg. After September 1899 operations were suspended, almost entirely owing to the Boer War, but on the 2nd of May 1901 they were started again. In 1905 the yield was valued at £20,802,074, and in 1909 at £30,925,788. So certain is the ore-bearing formation that engineers in estimating its auriferous contents feel justified in assuming, as a factor in their calculations, a vertical extension limited only by the lowest depths at which mining is feasible. On such a basis they arrived at more than £600,000,000 as the available gold contained in the Witwatersrand conglomerates. This was a conservative estimate, and was made before the full extent of the reefs was known; in 1904 Lionel Phillips stated that the main reef series had been proved for 61 m., and he estimated the gold remaining to be mined to be worth £2,500,000,000. Deposits similar to the Witwatersrand banket occur in Zululand, and also on the Gold Coast of Africa. In Rhodesia, the country lying north of the Transvaal, where gold occurs in well-defined quartz-veins, there is unquestionable evidence of extensive ancient workings. The economic importance of the region generally has been fully proved. Rhodesia produced £386,148 in 1900 and £722,656 in 1901, in spite of the South African War; the product for 1905 was valued at £1,480,449, and for 1908 at £2,526,000.
The gold production of Russia has been remarkably constant, averaging £4,899,262 per annum; the gold is derived chiefly from placer workings in Siberia.
The gold production of China was estimated for 1899 at £1,328,238 and for 1900 at £860,000; it increased in 1901 to about £1,700,000, to fall to £340,000 in 1905; in 1906 and 1907 it recovered to about £1,000,000.
| Year. | Australasia. | Africa. | Canada. | India. | Mexico. | Russia. | United States. |
Totals. |
| 1881 | 1,475,161 | .. | 52,483 | .. | 41,545 | 1,181,853 | 1,678,612 | 4,976,980 |
| 1882 | 1,438,067 | .. | 52,000 | .. | 45,289 | 1,154,613 | 1,572,187 | 4,825,794 |
| 1883 | 1,333,849 | .. | 46,150 | .. | 46,229 | 1,132,219 | 1,451,250 | 4,614,588 |
| 1884 | 1,352,761 | .. | 46,000 | .. | 57,227 | 1,055,642 | 1,489,950 | 4,902,889 |
| 1885 | 1,309,804 | .. | 53,987 | .. | 46,941 | 1,225,738 | 1,538,325 | 5,002,584 |
| 1886 | 1,257,670 | .. | 66,061 | .. | 29,702 | 922,226 | 1,693,125 | 5,044,363 |
| 1887 | 1,290,202 | 28,754 | 59,884 | 15,403 | 39,861 | 971,656 | 1,596,375 | 5,061,490 |
| 1888 | 1,344,002 | 240,266 | 53,150 | 35,034 | 47,117 | 1,030,151 | 1,604,841 | 5,175,623 |
| 1889 | 1,540,607 | 366,023 | 62,658 | 78,649 | 33,862 | 1,154,076 | 1,587,000 | 5,611,245 |
| 1890 | 1,453,172 | 497,817 | 55,625 | 107,273 | 37,104 | 1,134,590 | 1,588,880 | 5,726,966 |
| 1891 | 1,518,690 | 729,268 | 45,022 | 131,776 | 48,375 | 1,168,764 | 1,604,840 | 6,287,591 |
| 1892 | 1,638,238 | 1,210,869 | 43,905 | 164,141 | 54,625 | 1,199,809 | 1,597,098 | 7,102,172 |
| 1893 | 1,711,892 | 1,478,477 | 44,853 | 207,152 | 63,144 | 1,345,224 | 1,739,323 | 7,772,585 |
| 1894 | 2,020,180 | 2,024,164 | 50,411 | 210,412 | 217,688 | 1,167,455 | 1,910,813 | 8,813,848 |
| 1895 | 2,170,505 | 2,277,640 | 92,440 | 257,830 | 290,250 | 1,397,767 | 2,254,760 | 9,814,505 |
| 1896 | 2,185,872 | 2,280,892 | 136,274 | 323,501 | 314,437 | 1,041,794 | 2,568,132 | 9,950,861 |
| 1897 | 2,547,704 | 2,832,776 | 294,582 | 350,585 | 362,812 | 1,124,511 | 2,774,935 | 11,420,068 |
| 1898 | 3,137,644 | 3,876,216 | 669,445 | 376,431 | 411,187 | 1,231,791 | 3,118,398 | 13,877,806 |
| 1899 | 3,837,181 | 3,532,488 | 1,031,563 | 418,869 | 411,187 | 1,072,333 | 3,437,210 | 14,837,775 |
| 1900 | 3,555,506 | 419,503 | 1,348,720 | 456,444 | 435,375 | 974,537 | 3,829,897 | 12,315,135 |
| 1901 | 3,719,080 | 439,704 | 1,167,216 | 454,527 | 497,527 | 1,105,412 | 3,805,500 | 12,698,089 |
| 1902 | 3,946,374 | 1,887,773 | 1,003,355 | 463,824 | 491,156 | 1,090,053 | 3,870,000 | 14,313,660 |
| 1903 | 4,315,538 | 3,289,409 | 911,118 | 552,873 | 516,524 | 1,191,582 | 3,560,000 | 15,852,620 |
| 1904 | 4,245,744 | 4,156,084 | 793,350 | 556,097 | 609,781 | 1,199,857 | 3,892,480 | 16,790,351 |
| 1905 | 4,159,220 | 5,477,841 | 700,863 | 576,889 | 779,181 | 1,063,883 | 4,265,742 | 18,360,945 |
| 1906 | 3,984,538 | 6,449,749 | 581,709 | 525,527 | 896,615 | 1,087,056 | 4,565,333 | 19,620,272 |
| 1907 | 3,659,693 | 7,270,464 | 399,844 | 495,965 | 903,672 | 1,282,635 | 4,374,827 | 19,988,144 |
| 1908 | 3,557,705 | 7,983,348 | 462,467 | 504,309 | 1,182,445 | 1,497,076 | 4,659,360 | 21,529,300 |
Alloys.—Gold forms alloys with most metals, and of these many are of great importance in the arts. The alloy with mercury—gold amalgam—is so readily formed that mercury is one of the most powerful agents for extracting the precious metal. With 10% of gold present the amalgam is fluid, and with 12.5% pasty, while with 13% it consists of yellowish-white crystals. Gold readily alloys with silver and copper to form substances in use from remote times for money, jewelry and plate. Other metals which find application in the metallurgy of gold by virtue of their property of extracting the gold as an alloy are lead, which combines very readily when molten, and which can afterwards be separated by cupellation, and copper, which is separated from the gold by solution in acids or by electrolysis; molten lead also extracts gold from the copper-gold alloys. The relative amount of gold in an alloy is expressed in two ways: (1) as “fineness,” i.e. the amount of gold in 1000 parts of alloy; (2) as “carats,” i.e. the amount of gold in 24 parts of alloy. Thus, pure gold is 1000 “fine” or 24 carat. In England the following standards are used for plate and jewelry: 375, 500, 625, 750 and 916.6, corresponding to 9, 12, 15, 18 and 22 carats, the alloying metals being silver and copper in varying proportions. In France three alloys of the following standards are used for jewelry, 920, 840 and 750. A greenish alloy used by goldsmiths contains 70% of silver and 30% of gold. “Blue gold” is stated to contain 75% of gold and 25% of iron. The Japanese use for ornament an alloy of gold and silver, the standard of which varies from 350 to 500, the colour of the precious metal being developed by “pickling” in a mixture of plum-juice, vinegar and copper sulphate. They may be said to possess a series of bronzes, in which gold and silver replace tin and zinc, all these alloys being characterized by patina having a wonderful range of tint. The common alloy, Shi-ya-ku-Do, contains 70% of copper and 30% of gold; when exposed to air it becomes coated with a fine black patina, and is much used in Japan for sword ornaments. Gold wire may be drawn of any quality, but it is usual to add 5 to 9 dwts. of copper to the pound. The “solders” used for red gold contain 1 part of copper and 5 of gold; for light gold, 1 part of copper, 1 of silver and 4 of gold.
Gold and Silver.—Electrum is a natural alloy of gold and silver. Matthiessen observed that the density of alloys, the composition of which varies from AuAg6 to Au6Ag, is greater than that calculated from the densities of the constituent metals. These alloys are harder, more fusible and more sonorous than pure gold. The alloys of the formulae AuAg, AuAg2, AuAg4 and AuAg20 are perfectly homogeneous, and have been studied by Levol. Molten alloys containing more than 80% of silver deposit on cooling the alloy AuAg9, little gold remaining in the mother liquor.
Gold and Zinc.—When present in small quantities zinc renders gold
