GOLCON'DA. A ruined city and fortress in the Nizam's dominions, India, seven miles northwest of his capital, Hyderabad, in latitude 17° 22' N., and in longitude 78° 25′ E. (Map: India, C 5). The ruins of the ancient city, once the metropolis of the Kingdom of Golconda, the solid mausolea of its former sovereigns, which form a vast group at a distance of 600 yards from and overlooking the fortress, and the fortress itself, are all of great archæological importance and interest. The fort is now used as a State prison and as the Nizam's treasury. Golconda is proverbially famous for its diamonds, which, however, were merely cut and polished here, being generally found near the southern frontier of the Nizam's dominions.

GOLCONDA. A village and the county-seat of Pope County, Ill., 120 miles below Evansville, Ind., on the Ohio River and on the Illinois Central Railroad (Map: Illinois, D 6). It is a great poultry market, and has flour-mills, lumbermills, cooperage works, etc. Pop., 1900, 1140.

GOLD (AS., OHG. gold, Ger. Gold, Goth. gulp; connected with AS. geolu, Eng. yellow, Lat. helvus, grayish yellow, Gk. xλwpóc, chlōros, yellowish green, Skt. hari, yellow). A metallic chemical element, probably the first metal known to man. The alchemists regarded gold as the most perfect metal, compared it to the sun, and designated it by the same symbol by which they represented that orb; their efforts were constantly directed toward the transmutation of baser metals into pure gold. Gold is widely distributed in nature, and is frequently found native, though usually alloyed with silver and containing small quantities of copper or iron; it is also associated with palladium, rhodium, and bismuth. It is sometimes found crystallized, usually as octahedra or tetrahedra, but more commonly in thin lamina or grains in sand or gravel. Its presence in this condition is believed to have been caused by the disintegration of gold-bearing rocks, and it is readily collected from such alluvial sources by washing the auriferous soil. The purest specimens of native gold have yielded from 99.7 to 99.8 per cent. of the pure metal, the average California gold containing 88 per cent., while Australian gold sometimes runs as high as 96 per cent. pure metal. Gold also occurs in combination with mercury as electrum, with silver and tellurium as sylvanite, and with tellurium and lead as nagyagite. It is further found in various sulphides, as those of copper, lead, iron, and zinc; also in other ores, and in sea-water.

Gold (symbol. Au; atomic weight, 197.2) is of a bright yellow color when pure, and has a high metallic lustre. It is the most malleable of all metals, and has been hammered into a leaf 0.00009 millimeter in thickness. In this condition it appears green by transmitted light. Gold is very ductile, and can be drawn into wire so fine that 166 meters weigh but a single gram. Its specific gravity is 19.31, and it melts at about 1075° C. It is a good conductor of both heat and electricity. Whatever the temperature, neither water nor oxygen is capable of attacking it; and it is not affected by fusion with potassium chlorate. It yields, however, to alkalies and nitrates, and especially to sodium or potassium cyanide. It is not dissolved by any single acid, except selenic, but readily passes into

solution when treated with aqua regia (a mixture of nitric and hydrochloric acids), or with other acid liquids in which chlorine or bromine is evolved. Pure gold, being too soft for all ordinary purposes, is generally alloyed with other metals. With copper it yields a reddish alloy, which is quite hard; the standard metal used for coinage is made up of eleven parts of gold and one of copper. With silver it yields so-called 'white alloys,' which are used for jewelry. It combines readily with mercury, forming a white amalgam of a pasty consistency. The most extensive uses of gold are for coinage, for jewelry, for gilding frames, furniture, books, etc., for electroplating, and in dentistry.

COMPOUNDS. With oxygen gold forms a monoxide, or aurous oxide, and a trioxide, or auric oxide. The former is obtained by decomposing aurous chloride with cold dilute potassium hy droxide; the latter by heating a solution of gold trichloride with an excess of magnesia and well washing the precipitate with nitric acid. Auric oxide, which is the more common of the two, combines with bases, forming salts called aurates. Perhaps the most important of the compounds of gold with acids is auric chloride, which is readily obtained by dissolving metallic gold in aqua regia and evaporating the solution to crystallization. The resulting orange-red crystals may be further purified by recrystallization. It is a very deliquescent salt, and is chiefly employed for toning silver prints in photography.

Fulminating Gold, which was originally described in a work published under the name of Basil Valentine, is a green or brown powder that readily explodes when dry; it may be obtained by the action of ammonia on gold hydroxide, or by precipitating gold chloride with ammonia or

its carbonate.

Gold Purple, or Purple of Cassius, which was originally prepared by Andreas Cassius, and described in 1685, is a flocculent purple precipitate obtained by treating a solution of stannous and stannic chlorides with gold chloride. The resulting product is believed to be a mixture of tin oxide and finely divided gold. The color of ruby glass is due to small proportions of this pigment.

Mosaic Gold is a fine flaky yellow variety of tin bisulphide; it is prepared by heating a mixture of seven parts of sulphur, six parts of ammonium chloride, and eighteen parts of a powdered amalgam consisting of two parts of tin to one of mercury. When the odor of hydrogen sulphide is no longer perceptible, the heat is raised to low redness, and the mercurous chloride, ammonium chloride, and mercuric sulphide are volatilized. The mosaic gold thus obtained is used as an imitation bronze in the arts.

PRODUCTION OF GOLD. The supply of gold in ancient times was derived mostly from surface deposits of sands and gravels which yielded their values by simple processes of washing. Gold was thus mined at a very early period in India, Central Asia, the southern Urals, and in the region bordering the eastern Mediterranean. With the progress in metallurgical knowledge attention was directed to the exploitation of auriferous veins, a branch of the industry which seems to have attained to some importance before the opening of the Christian Era. Ancient workings of this character, ascribed to the Egyptians, have been found in the mountains of Nubia; and

Dr. Karl Peters has described recently extensive mines in the interior of South Africa, not far from the gold-fields of Rhodesia-a locality believed by Dr. Peters to be the Ophir of the Israelites. The Romans operated mines in Hungary, Spain, and Great Britain at various periods. During the Middle Ages the mining industry seems to have made little progress. It is estimated that the total stock of gold in Europe when America was discovered did not exceed $225,000,000. From this time on, however, there has been a gradual though not uninterrupted increase in production, as may be seen from the following table:

WORLD'S PRODUCTION OF GOLD SINCE 1492

These statistics have been compiled by the late Adolf Soetbeer and by the United States Mint from the most authoritative sources. The total output for the entire period of 413 years is equivalent at the coinage value of $20.67 per ounce to 565,287,000 troy ounces, or approximately to 18,840 short tons. The production since 1850 has exceeded that of the preceding three and a half centuries. Along with the discovery of new gold-fields have come improved processes for treating low-grade and rebellious ores, such as the cyanide and chlorination processes, and a more systematic adaptation of mining and metallurgical establishments to the varying natural conditions. It is specially noteworthy to observe that during the last decade the yearly production of gold in the world has doubled."

The important gold-producing countries at the present time are the United States, the Transvaal Colony, Australia, Russia, Canada, and Mexico. In 1905 their combined output was about 85 per cent. of the world's total. The distribution of the production in 1905 by countries is shown in the table following, compiled by The Mineral Industry.

UNITED STATES. In the United States, as elsewhere, the occurrence of gold is limited to areas of crustal and volcanic disturbances, these apparently being the prime factors that govern the formation of ore bodies the world over. There are thus two distinct regions in which gold is produced, the eastern region along the Appalachian Mountains, and the western or Cordilleran region. Gold has been found at numerous localities on

Africa:

Rhodesia. Transvaal West Coast

Asia:

Korea...

Malay Peninsula..

Australasia

Other Countries...

Total

1 The Mineral Industry, Vol. XIV. (1906). quartz and surface deposits are worked, but the former are the most important at present. The veins cut through slates and schists, and carry iron and copper pyrites. Dahlonega, Ga., and Haile Goldmine, S. C., are the chief mining centres. The Western gold-fields are scattered over the whole region between the eastern foothills of the Rocky Mountains and the western slopes of the Sierra Nevada and Cascade Ranges.

The auriferous belt of California extends through the northern and central parts of the State, and from the summits of the Sierras to the San Joaquin and Sacramento valleys. Its wonderful richness has furnished the incentive for the exploration and rapid development of the whole Far West. From the first discovery in 1848 to

United Kingdom.

13,584

280,781

348,518

7,203,864

58,055

1,200,000

1905 the output has amounted to $1,435,000,000, or about one-eighth of the entire output of the world since 1492. The gold occurs in three types of deposits: River gravels or placers, high gravels, and veins. The river gravels, found in the beds of the numerous streams that flow down the western slopes of the Sierras, have been derived from the higher levels, where the erosive processes have cut deeply into the auriferous rock formations. Most of the gold is generally found near bed-rock, and it is necessary to remove a heavy overburden before the values can be obtained. The gold particles vary from minute pellets or dust to nuggets of considerable size. The high gravels represent the work of ancient rivers whose channels are more or less parallel to those of the present day, but have been filled in with detrital materials and frequently buried beneath lava flows. They lie along the higher slopes of the Sierras up to 5000 feet above sea-level, and sometimes attain a thickness of 500 feet. The veins, which have furnished the gold found in both the placers and high gravels, occupy fissures in slates, schists, and igneous rocks, and are, of variable extent and richness. Quartz is generally the gangue material, while the gold occurs in a free state or combined with sulphides, most commonly pyrites. A great series of these veins, called the 'mother lode,' extends across Tuolumne, Calaveras, Amador, and El Dorado counties; for a number of years it has been the source of much of the gold mined in the State. The Comstock Lode (q.v.) is situated on an eastern spur of the Sierras, extending into Nevada. Placers and veins similar to those of the Sierras are found also in Oregon and Washington.

The Rocky Mountains and the outlying ranges, which were first prospected by Californian miners in the early sixties, include an immense area of gold-bearing territory. Rich gravels have been worked near Leadville, Fairplay, and in San Miguel County, Colo.; near Helena and Butte, Mont.; along the Snake River, Idaho; near Deadwood, S. D.; and at Santa Fé, N. M. Leadville was originally settled by gold-miners, but the chief industry for a long time has been the mining of lead-silver ores; it is now coming to the front again as a gold-producer. About 1890 important discoveries of telluride ores were made in the granite hills surrounding Pike's Peak, and since then Cripple Creek has become the centre of the richest gold field in America. In 1905 approximately $18,000,000 in gold was taken from these deposits. The Black Hills of Wyoming and South Dakota have a well-developed mining in dustry which is based largely upon the occurrence of extensive but low-grade ore bodies. Much of the ore is refractory, yielding only a portion of its gold to amalgamation, so that large cyanide plants have been installed here. In Nevada the Tonopah and Goldfield districts have recently been developed into active mining camps, which produce the greater part of the State's out put. The ore is chiefly of high grade. There are numerous small fields in Montana, Utah, Idaho, Arizona, and New Mexico, which in the aggregate yield considerable amounts of gold annually. See Map with UNITED STATES.

Alaska, the seat of the most recent discoveries, gives promise of great future importance. With the exhaustion of the rich placers and beach deposits, such as were found at Cape Nome and in the interior districts, attention will be directed to

quartz mining, which affords a more permanent basis for the industry. It is noteworthy that the Territory was a producer of gold several years before the surface deposits were discovered; the quartz mines on Douglas Island, near Juneau, have yielded a large output from ore that averages only $2 per ton.

CANADA. The rich alluvial deposits of Yukon Territory furnish the larger part of the output, the remainder coming from British Columbia, Ontario, and Nova Scotia. In the Yukon region the gold is concentrated in the recent gravels along the rivers and in the terraces on the sides of the valleys. A few quartz veins have been found, but so far the production from this source is small. See YUKON GOLD-FIELD.

RUSSIA. Most of the gold is derived from placer workings on the eastern slope of the Urals. Little progress has been made in the introduction of improved methods and appliances, and only the richer deposits can be exploited at a profit. There are small quartz mines in the interior districts of Siberia.

TRANSVAAL COLONY. The Witwatersrand goldfield, near Johannesburg, is one of the most remarkable and productive in the whole world. The deposit is a conglomerate, commonly called 'banket,' varying from a few inches to several feet in thickness and averaging about $10 per ton in gold. It can be traced for several miles along the strike, and, as it retains its auriferous tenor with depth, there is an enormous reserve of ore for future working. The output of the Transvaal mines in 1905 was $101,225,558, the largest output in the world. The amount of gold ore for future working runs into billions of dollars.

AUSTRALIA. Gold-mining holds a prominent place among the industries of the Commonwealth. The rich alluvial deposits that first attracted the attention of miners are largely exhausted, but there are still considerable areas of surface gravels which repay working with modern methods. An increasing proportion of the output each year comes from quartz veins. The most productive fields are those of Murchison and Coolgardie in Western Australia; Charters Towers and Mount Morgan in Queensland; and Ballarat, Sandhurst, and Beechworth in Victoria.

GOLD-MINING. Gold-mining operations may be divided into two classes, which are commonly called placer mining and quartz mining. The deposits of gold first mined were called placers, and were the river-bed deposits of gold-bearing sand and gravel. These deposits are known as dry placers when they are ancient river-beds from which the water has gone, and as wet placers when they are the beds of existing streams. The process of dry-placer mining consists in excavating the gold-bearing sand and separating the gold from it by washing, according to one of the methods described in the succeeding section on Metallurgy. Dry-placer workings are divided into surface placers and deep placers. The most important method of placer mining is the hydraulic method, which was first attempted in a crude way in 1852 in Placer County, Cal., and is now practiced on an immense scale. Briefly described, hydraulic mining consists in directing a powerful stream of water from a pipe against the gold-bearing gravel bank, which breaks down the material and washes it away through sluices, where the separation of metal is accomplished as described below. Wet-placer mining from the