Gold , a precious metal, ranking the first in beauty and value among useful metals from the earliest times to the present day; distinguished for being the only metal of a yellow color, and for possessing in the highest degree the properties of ductility and malleability. In chemistry its symbol is Au, from the Latin au-rum, gold; its equivalent number 98.5, or, in the usage of many chemists, the double of this, 107. Its density varies according as the metal is more or less compressed; it is rated when hammered at from 19.258 to 19.4. In a finely divided state, precipitated from its solution by sulphate of iron, it has proved of specific gravity 20.72. When pure the metal is nearly as soft as lead, and is then susceptible of its greatest extension by beating or wire-drawing. (See Gold Beating.) In thin leaf it is transparent, and the transmitted light is of a green color; by heat the color is changed to ruby red, and this color the metal finely divided imparts under certain conditions to glass. Its melting point is variously given as 2010° F., 2192°, 2518°, and 2590°. In the heat of furnaces it is not volatilized; but gold wire is dispersed in vapor by the oxyhydrogen blowpipe, by the heat of the sun's rays concentrated by a powerful convex lens, or by the electric battery.
As the current traverses it, the vapors produced may be collected upon a sheet of paper placed beneath the wire; the paper is stained a purplish brown by the deposit of finely divided gold, and a sheet of silver may be thus gilded. When gold is fused in large quantity and allowed to cool slowly, cubical crystals are sometimes observed to form, and crystals of native gold have been found in the form of the regular octahedron. Gold is not acted upon by alkalies or simple acids, except selenic, nor by the oxygen of the air even when long exposed in a fused state. Neither does sulphur affect it: but it is dissolved by bromine and chlorine, or by any combination of acids or other substances in which free chlorine is present. This element, as it is generated in mixtures, is a powerful solvent of gold; and to it is due this property of the compound called aqua regia, formed of 4 parts of hydrochloric and 1 part of nitric acid. Gold forms alloys with most of the metals. Silver or copper increases its hardness and renders it better adapted for wear when used for coins, jewelry, or plate. Such compounds are also more fusible than pure gold. The solder for gold trinkets is 1 part of copper to 5 of gold, or to 4 of gold and 1 of silver. With mercury gold unites to form an amalgam.
Mercurial fumes even, coming in contact with gold, instantly combine with and whiten it. The mercury may be driven off by heat. (See Amalgam.) Gold is obtained from its solutions in various forms. The precipitate by sulphate of iron is a dull brown powder, which by pressure acquires the metallic lustre and color. The precipitate by oxalic acid is yellower and more metallic in appearance. The metallic gold which is left on evaporating a solution of its compound with chlorine and heating the residue is of a spongy character and dull hue; by annealing it becomes more dense and yellow, and by percussion is readily welded together. (For modes of preparing sponge gold and its uses, see Dentistry.) - Gold is very widely distributed in nature, and late researches have shown that it is present in appreciable quantities in the waters of the ocean, where it is associated with silver. According to Sonstadt, a ton of sea water yields by a simple chemical process a grain of gold; so that the quantity of the precious metal thus held in solution must be vastly greater than all the gold ever yet extracted from the earth. Gold is very generally diffused throughout the solid rocks, though only here and there accumulated in sufficient quantities to be economically available.
The workable deposits of this metal are in stratified rocks of different formations, from the oldest crystallines to the postpliocene sands and gravels, and also in veins traversing rocks of various geological periods. The most common veinstone of gold is quartz, but it is also found in bitter spar and disseminated in metallic sulphides, such as iron pyrites, which very often contains sufficient quantities of the metal to be extracted with profit. In this as well as in the quartzose gangues the gold is sometimes in large grains or crystalline threads or masses, and sometimes disseminated in particles invisible to the eye. The opinion is entertained by many that in pyrites and in other sulphuretted ores the gold is sometimes chemically combined with the other metals and with sulphur. It has been found that the lead of commerce, from whatever source derived, is seldom or never without a trace of gold. Gold is not, as has been erroneously supposed, confined to rocks of any one geological period. The gold of Colorado is found in veins with metallic sul-phurets traversing crystalline rocks of eozoic age, and the same is the case in Ontario; while the gold-bearing strata of the Appalachians are in large part if not wholly of pre-palaeozoic age, as are those of the Alps and the Ural mountains.
In Nova Scotia, on the contrary, the gold-bearing rocks are slates and sandstones, supposed to be of lower Cambrian age; and the auriferous strata of Wales as well as those of Australia are of that period. The gold-bearing veins extensively worked in Transylvania traverse sandstones of eocene or early tertiary age, and the gold-bearing quartz of California is said to be found in strata of the Jurassic formation. It is probable, however, that a part of the auriferous rocks of that country will be found to be eozoic, while on the other hand it appears that the silicious deposits now forming from the thermal waters in Nevada contain not only metallic sulphurets but small portions of gold; so that the processes which in former times gave rise to gold-bearing veins in that region are still in operation. - By the disintegration and crumbling away of the rocks which contain the auriferous veins, the contents of these are swept down to lower levels, and the gold by its density always seeks the lowest places among the moving materials. Thus are produced the auriferous gravel deposits in alluvial formations, the golden sands of the rivers; and so have they been gathering for long ages past and forming deposits, some of which are now seen in situations apparently out of reach of such agencies.
In these deposits, when stripped of the clay and sands which cover the lower and richer layers, there are found in the irregular-shaped cavities of the surface of the rock, in pockets and in piles against the projecting strata, the accumulated riches of ancient veins, it may be, of vast extent. By washing away the intermixed earthy and stony matters, the metal is obtained in dust, flattened scales, small lumps, and nuggets of all sizes and shapes, the larger pieces rounded by attrition, or ragged from the irregular forms they held in their original hard quartz matrix. Their size is commonly greater than that of gold found in the veins near by, a fact first explained by the late Oscar Lieber of South Carolina to be due to the solution of gold . and its subsequent aggregation. Later observations of Genth and Selwyn go to confirm this view. In these deposits the largest lumps of gold ever met with were discovered, as that of Cabarrus co., N. C, of 28 lbs. avoirdupois, or 37 lbs. troy, found in 1810; the mass weighing 90 lbs. troy in Zlatoust, a district of the southern Ural, in 1842, and now in the imperial school of mines at St. Petersburg; a mass from Victoria in Australia, which was exhibited in London, and weighed 140 lbs. 3 dwts. troy, of which 6 oz. only were estimated as matrix; and the still larger mass found at Bal-larat in that region, and weighing 2,217 oz. 16 dwts., or about 185 lbs. troy.
According to Phillips, the largest piece of gold ever found was probably the great Australian nugget, known as the "Sarah Sands," which weighed 233 lbs. 4 oz. troy. Though in a metallic state, gold is never obtained pure; silver is always alloyed with it, but in no definite proportions. The purest specimen is probably one from the Ural, near Yekaterinburg, analyzed by Rose, which gave, in 100 parts, gold 98.90, silver 0.16, copper 0.35; its specific gravity was 19.099. The product of California is much of it very near the richness of gold of the American and French gold coins, which is 900 parts in 1,000. Its average, however, is stated to be 875/1000 to 885/1000, and that of Australia 960/1000 to 966/1000. A specimen of California gold, containing gold 90.70, silver 8.80, and iron 0.38, was of specific gravity only 14.0, and by fusing this was increased to 17.48. Gold from the Chaudiere, Canada, of specific gravity 17.60, analyzed by T. Sterry Hunt, gave gold 87.77, silver 12.23; another specimen in fine scales, of specific gravity 16.57, produced gold 89.24, silver 10.76. Copper, palladium, and rhodium are also met with as alloys of gold.
In Transylvania veins are worked producing an alloy of tellurium, gold, silver, and antimony; the tellurium commonly constitutes from 55 to 60 per cent., and the gold from 25 to 30 per cent. The same compound has been recognized at Gold Hill, N. C. Gold occurs in a few other combinations also with tellurium. - In the oldest records of the human race mention is made of gold, and like silver it was enumerated as an element of riches. Throughout the Old Testament there are frequent allusions to gold and to fine gold. It was beaten into thin plates, cut into wires, and even woven with threads of linen for the sacerdotal robe of Aaron. It was fashioned into breastplates with chains at the ends of wreath-en work of pure gold; and it was used as the setting of precious stones. By other nations it was made into gods and idols, some of gigantic size. Aaron prepared a golden calf for the children of Israel, which Moses burned with fire and reduced to powder; an operation that might have been effected by first melting and beating it out into plates. In building the temple of Jerusalem the quantities of gold lavishly employed by Solomon for its furniture and decorations implied that it was largely collected, and that the ancients had access to mines of great extent and richness.
Atahuallpa, the captured inca of Peru, agreed to bring together for his ransom, in the space of two months, articles of gold which should fill a room 22 ft. long and 17 broad to the height of 9 ft. When this was done and the gold melted, it was found to amount to l,326,539 pesos de oro. The commercial value of the peso, according to Prescott, was equivalent to $11 67, making the sum total $15,480,710. The source whence the Phoenicians and Israelites derived their immense supplies of gold was the land of Ophir, a region still of uncertain locality. Once in three years the fleet of Solomon completed a voyage to it and back. Its other products besides gold brought back to Palestine (1 Kings x. 11 and 22), as ivory, spices, precious stones, ebony, peacocks, apes, and the almug or sandal wood, indicate that it was in the tropics. It is generally presumed to have been either the East Indies or that part of the S. E. coast of Africa called Sofala by the Arabs. The auriferous character of the desert steppes of Gobi was known in the time of Herodotus to the inhabitants about the sources of the Indus; and to this day are to be seen along the southern Ural the works of ancient mining operations, supposed to be those of the nomadic Scythians. Ethiopia and Nubia also were largely productive of gold; and the ancient mines discovered by Belzoni in the Zabarah mountains are supposed to have furnished to the Pharaohs of Egypt their abundant supplies.
Thus many auriferous regions appear to have been known at different times, as productive as those of the prosent period. While the gold of the deposits continued abundant they were vigorously wrought, and each district furnished in its turn the principal share of the production of the world. In the time of the Romans the precious metals were not so abundant, though rich deposits were worked along the foot of the Pyrenees, and in some of the provinces bordering the Alps. Stra-bo (B. iv. ch. 0, sec. 12) refers to the statement of Polybius that in his time the gold mines near Apulia were so productive that the value of gold was reduced one third in Rome. Spain, too, had its deposits worked in ancient times along the Tagus; and the Athenians gathered their supplies of the metals from Thessaly and the island of Thasos. In the middle ages the art of working gold appears to have been little practised. The richness of the known mines was comparatively exhausted, and previous to the opening of the new fields following the discovery of America, the attention of metallurgists was directed to vain attempts to transmute the baser into the precious metals.
It, was estimated that at the time of the discovery of America the gold and silver in the old world, exclusive of the more or less unknown regions of the East, was reduced to about £34,000,000, and that the supply no more than met the loss by wear. The enormous importation of gold and silver from the new world soon made up the deficiencies of the old mining regions, and. reducing the value of the metals in comparison with other products, caused mines which had before been successfully worked to be abandoned as unprofitable. From 141)2 to 1500 the annual amount of gold brought into Europe from America is rated by Humboldt at £52,000; till 1519 gold only was obtained. The same proportion may safely be extended to the year 1521, when Mex-ico was conquered, and the precious metals, but more especially silver, were obtained in vastly larger quantities. The mines of Potosi, discovered in 1545, gave a still greater preponderance to the production of silver, and no data are afforded for afterward distinguishing the relative proportions of the two metals. But in the first 300 years succeeding the discovery, the receipts of American gold were estimated at 3 1/2 times the product of the mines of the old continent, and those of silver at 12 times the product of this metal.
In the time of Queen Elizabeth gold was obtained at Lead-hills in the south of Scotland; and toward the close of the last century, in the county of Wick-low in Ireland, about $50,000 worth of gold was collected in two months. These deposits soon, however, proved unprofitable. The metal was in ancient times collected in Cornwall, and is known to exist in Devonshire. The largest portion of British gold has been the product of Wales, the principal gold-bearing district of which is confined to an area of about 25 sq: m. in North Wales. The mines are still worked, but there has been a great decrease in the production. Upon various rivers of Europe, as the Rhine, the Rhone, the Danube, the Reuss, and the Aar of Switzerland, the sands were known to be auriferous in places, but too poor to pay the expenses of working. In Hungary veins containing gold disseminated in ores of sulphuret of silver are worked in a partially decomposed feldspar of the trachytic formation, and also in syenite and porphyritic greenstone; and gold is also extracted from auriferous pyrites of trap rocks of the most recent formation. The mines of Nagy-Ag and Zalatna in S. W. Transylvania produce the alloy of tellurium and gold before referred to.
Besides gold, the Hungarian mines, worked by the Austrian government, produce copper, silver, mercury, antimony, lead, iron, and cobalt. In the Austrian provinces of Salzburg and Tyrol, at Bockstein and at Zell, gold is extracted from poorer ores than arc elsewhere ever found profitable to work. The quartz gangue of the veins and the argillaceous slates of the walls contain auriferous pyrites, argentiferous mispickel, gray argentiferous copper, and sulphuret of silver. From these the gold is profitably extracted when it amounts to only from 6 to 15 parts in 1,000,000. At Zell it has been stated that the annual product of 50,000 quintals of ore has been only 35 marks of gold, or 4 parts in 1,000,000. The silver, though obtained in six or seven times the quantity of the gold, is still less than half its value. The total production of the Austrian mines for several years past has averaged from 5,500 to 5,800 oz. per annum. In Italy various localities were known to the ancients as producing gold.
At present the only mines of consequence are in Piedmont, in the valleys of Anzasca, Toppa, and Antrona, and to a less extent in those of Ala-gna, Sesia, and Novara. In Lombardy the chief mines are at Peschiera and Minerva di Sotto. The ore is an auriferous pyrites containing about 12 dwts. of gold per ton. The total yield of all the mines does not exceed $100,000 per annum. In France a small amount of gold is produced, chiefly from aurif-erous galena; and there are deposits in Savoy. Gold mines have been worked in Spain from very remote periods, but the present annual production does not exceed about $10,000. The mines of the Asiatic slopes of the Ural extend along the secondary ridges of the chain in a N. and S. direction more than 400 m. The crystalline rocks here contain veins, one of which is successfully worked at Berezov, near Yekaterinburg, by shafts and levels. The gangue is pyritiferous quartz with oxide of iron resulting from its decomposition, and the rock is a partially decayed granite, the quartz remaining in angular grains; the adjoining formations are talcose and chloritic slates. All the other workings of Russia are alluvial mines.
These are not only in the Ural district, where they have been worked for more than a century, but during the reign of Nicholas a region of southern and eastern Siberia, estimated to be as large as all of France, was found to be more rich in gold than that of the Ural. From the great E. and W. chain of the Altai mountains, which lie between Siberia and Mongolia, low ridges are directed toward the north into the governments of Tomsk and Yeniseisk, and these ridges of crystalline rocks are the reposi- , tories of the precious metals. In 1843 this region produced the value of about $11,000,000, while the product of the Ural districts for the same year was only about $2,500,000. Until the discovery of the mines of California it made Russia the greatest gold-producing country of the world. The average production of the Russian mines amounts to about $15,000,000 annually; and their total production from their discovery about 1745 to 1874 may be stated in round numbers at $600,000,000. The product in 1865 was given by Phillips at 09,500 lbs. troy. - Little is known of the other gold regions of the continent of Asia. The metal is possessed, and its deposits are no doubt worked to considerable extent, by all the principal nations; but except from the islands of the Indian archipelago little of it falls into the general circulation of the world.
The river Pactolus of Asia Minor is supposed to have furnished from its golden sands the foundation of the wealth of Croesus. According to Pumpelly, who made geological researches in China, Mongolia, and Japan during 18G2-'5, gold exists in numerous localities in no fewer than 14 of the 19 provinces of China. The richest regions appear to be in the province of Szechuen and along the branches of the Knenlun mountain range, which, extending in a general E. and W. direction, penetrate far into central China, between Szechuen and the Wei river. There are also numerous washings at the base of the watershed between Kweichow and Hunan, and through the centre of Shantung from S. W. to N. E. In these localities placer gold is found, and some of them are mentioned as furnishing nuggets; but little is known of the production of these washings. It is said that extensive sources of gold have long been known in China, but that the working of the mines has been discontinued by the government in accordance with some of their financial theories.
The gold-bearing formations of eastern Siberia are believed to extend into Chinese Tartary, and to connect with those of central and southern China. For several centuries Japan has ranked high for its production of gold, which constituted a chief article of the commerce carried on by the Portuguese and Dutch traders. According to a Japanese authority, the value of the gold exported from Nagasaki from 1611 to 1700 amounted to $08,000,000, and of silver to $157,000,000; while Hildreth states that the value of the precious metals exported from Japan during the two centuries beginning with 1540 could not have been less than $200,000,-000. But little is known concerning the present production of gold in the empire, or the localities where it exists. The gold regions on the island of Yesso were surveyed in 1802 by Blake and Pumpelly, while in the service of the tycoon's government. According to Blake, the gold region extends along the Kunui and Pusibets rivers and in the range of mountains dividing Volcano bay from the west coast. Deposits are also supposed to exist in the northern and interior portions of the island. No veins have yet been found, the gold being obtained from washings.
It is in fine scales, and occurs in the gravel along the streams; it is also found in high terrace deposits on the hillsides. The annual product of the island does not probably exceed $25,000. There are also extensive mines upon a large vein of mixed silver and gold ore on the island of Sado, off the N. W. coast, which is supposed to have furnished a large amount, but the facts regarding it are jealously guarded by the Japanese. Gold is largely used in Japan for gilding, for inlaying and overlaying metals, and for alloys with copper and silver of various colors and degrees of fineness. Gold has long been found in abundance in Borneo; according to Kloos, the metal occurs in varying quantities throughout the entire island. Placer gold is found on the river Kapola, associated with iron ores, sulphuret of antimony, and diamonds. The production of gold has also been reported in India, Thibet, Ceylon, Sumatra, Celebes, and the Philippine islands. - Africa is believed to have been the source of a largo proportion of the gold possessed by the ancients, and is reported by modern travellers to be*still rich in it. The unmanufactured gold obtained from that country is in the form of dust, evidently obtained from alluvial washings.
Russegger, who travelled through Nubia in 1838, reported the mountain chain extending across the interior of Africa from E. N. E. to W. S. W., and the streams flowing from it, to be auriferous. In Sennaar and southern Abyssinia gold occurs in placer deposits and in quartz veins traversing granite, gneiss, and chloritic slates. The greatest portion of the gold brought to the coast is from the fields of Bambook, south of the Senegal, the most important mines in Africa. There is a gold district in Kordofan on the upper Nile, between Darfoor and Abyssinia, and it is obtained in small quantities opposite Madagascar. A few years ago the annual production of Africa was estimated by Birkmyre at 4,000 lbs., valued at about $900,000. In 1800 the existence of extensive gold fields in south Africa, between lat. 17° and 21° 30' S., was discovered by Hartley, an elephant hunter, and a German scientific traveller named Mauch. The gold fields occupy the interior region between the Zambesi, W. of Tete, and the middle course of the Limpopo river. The distance to them from the Portuguese settlement of Sofala is about 350 m. The region containing the gold is an elevated table land about 7,000 ft. above the sea; it is chiefly occupied by the Matabele section of the Caffres, a warlike tribe.
The travellers above named found beds of glistening white quartz rock extending over this table land, which were found upon examination to contain gold. Particles of gold were also found along the sandy margins of rivulets. It is supposed by some that these mines were known to the Portuguese as early as the 17th century, and by others that here was the Ophir of Solomon. Although the discovery of the south African gold fields attracted considerable attention, the production hitherto seems to have been unimportant. - The first known discovery of gold in Australia was made by Count Strzelecki in 1839, and by him communicated to Sir George Gipps, then governor of the colony of New South Wales. In deference to the wishes of the latter, who was of opinion that a widely spread knowledge of the existence of gold would prevent the maintenance of discipline among the 45,000 convicts there collected, the discovery was not proclaimed to the world. It was rediscovered in 1841 by the Rev. W. B. Clarke, a geologist, upon whom also silence seems to have been enjoined by Governor Gipps. Without knowledge of these discoveries, it is said, Sir Roderick Murchison in 1844 publicly asserted the high probability of the existence of gold in Australia. It is also said that gold was found at Clunes, Victoria, in 1850. The discovery, however, which led to the extensive working of the mines was made in 1851 by Mr. E. 11. Hargreaves, who had just returned from California, and at once began prospecting near Bathurst on the Macquarie river, New South Wales, where gold was found in considerable quantities.
The announcement of this fact caused much excitement and a sudden immigration of great magnitude to this region. (See Emigration). The government at once laid claim to the land and began to grant licenses to dig for gold. The gold region was soon traced along the range of hills N. and S., and new discoveries were made of deposits surpassing all the rest in richness in the colony of Victoria, near the southern coast, 70 m. N. W. of Melbourne. In October there were 7,000 persons engaged in the new diggings at Balla-rat near Mt. Buninyong, occupying less than a square mile in extent. The next month many of these were drawn off to the still richer deposits about Mt. Alexander in the same region, where it was estimated that 10,000 persons were then employed. In December 63,300 oz. were transported to Melbourne from this locality, which was then valued at £3 19s. 6d. per oz. The whole amount conveyed from the two localities from Sept. 30 to Dec. 31 was 124,835 oz.; the whole product of the colony was 345,146 oz. The immigration the next year of 104,000 more than doubled the population of Victoria; still richer diggings were discovered at Ben-digo, and the total product of the colony for the year 1852 was estimated at 4,263,042 oz.
The estimates made in London of the whole amount of gold exported from Victoria and New South Wales up to the close of 1852 gave for the former a total value of £16,000,000, and for the latter £3,500,000; or for 15 months nearly four times what the annual production of the world was supposed to be five years previously. The richest and most extensive gold fields of Australia are in the colony of Victoria, where the area of the mining region is about 725 sq. m. This is divided into the mining districts of Ballarat, Beechworth, Sandhurst, Maryborough, Castlemaine, and Ararat. In Australia, as in California, gold is directly obtained from three distinct sources, viz.: shallow placers, deep diggings, and quartz veins. The estimated number of quartz veins in Victoria is about 2,000. According to Selwyn, "these veins, traversing lower paleozoic strata and associated with granitic and igneous rocks, are, so far as at present known, the primary source of the whole of the gold raised in Victoria. The thickest and most persistent veins, or lines of reef, are found on the lower or older portions of the series; but the average yield of gold per ton of stone has, I believe, been greater from the thinner veins of the upper beds." The thickness of these veins, which are described as "dikes or reefs," varies from that of a thread to 130 ft.
They have a general meridional direction, and are inclined either east or west at angles varying from horizontal to vertical. Frequently they occur in the planes of cleavage, occasionally between those of the strata, and they often intersect both. These veins have been worked to a depth exceeding 600 ft., and it has been found that the yield does not decrease with increase of depth. Mr. Selwyn has reached the conclusion that at least two distinct sets of quartz veins exist in Australia, one of which is entirely barren, and that they have been formed at two different and remote periods, the barren being the older one. This view is corroborated by the fact, well known to experienced quartz miners in Australia, that in many districts barren and rich quartz ledges are found in close proximity. As this same phenomenon has been noticed in California and the Appalachian gold field, it suggests, according to Blake, the probable existence of quartz lodes of two or more distinct periods in America as in Australia. The greater portion of the gold obtained in Australia is from gravel deposits or placers similar to those in California. They occur in beds of streams, along the banks, and in ancient channels running transversely to the existing drainage of the country.
Rich deposits are found under heavy accumulations of stratified tuffs and lavas overlaid with table mountains of basalt. The thickness of the placer deposits varies greatly in different places, ranging from 100 to 400 ft. The ratio of gold obtained from quartz mines to that of placers is indicated by the production of the two kinds in Victoria in 1866, viz., 521,017 oz. of quartz and 958,177 oz. of placer gold. The most productive gold fields of Victoria have been those of Ballarat and Bendigo. The general description of the gold fields of Victoria will apply to those of New South Wales. The alluvial deposits, however, are not so extensive as in Victoria, and the production of the colony has been less. South Australia and Queensland are also gold-producing, but the amount obtained is small. The Australian gold has a higher color and is finer than that from California. Its fineness ranges from 20 to 23.5 carats, the Ballarat gold being of the highest standard. The Ballarat nugget mentioned above, found in1858, and weighing 2,217 oz. 16 dwts., was exhibited at the Paris exposition of 1867, and valued at nearly £10,000. Gold was first discovered in New Zealand in 1842; further discoveries were made there in 1851, and in 1856 mining operations on an extensive scale were begun.
The rock formations and alluvial deposits, which are deep and extensive, are similar to those in Australia. - In the United States there are two extensive auriferous regions or gold belts, one on the Atlantic slope, known as the Appalachian gold field, and the other on the Pacific coast, embracing California and the neighboring states and territories. The Appalachian gold field extends southwesterly from Virginia through North Carolina, South Carolina, and Georgia, and also includes portions of Alabama and Tennessee. The width of the gold range varies greatly; in some places it exceeds 75 m. The metal does not exist in a continuous belt extending through this region; but there are numerous auriferous tracts, occurring at intervals and generally parallel with each other, though often many miles distant. In North Carolina, from which the greatest amounts of gold have been obtained, there are two principal belts extending across the state in a S. W. and N. E. direction; one through Mecklenburg, Cabarrus, Rowan, Davidson, Guilford, and Caswell counties, and the other through' Rutherford, McDowell, and Burke counties.
The latter is the more westerly of the two, being from 10 to 20 m. distant from the base of the Blue Ridge; it is also more elevated, while the placer deposits are richer and more extensive than in the E. belt. In Georgia also the range appears to be divided into two belts, which are separated by unproductive rocks. Quartz veins closely resembling those of California are found in these regions. The gold is either free in coarse grains, or in fine particles disseminated in sulphuret of iron or copper. The gold veins of Virginia extend through Fauquier, Culpeper, Louisa, Fluvanna, Buckingham, and a few other adjoining counties. The production at times has been very large, but the veins have been extremely fluctuating in their yield; and though some of these still continue to be worked, their history on the whole is by no means favorable. Though gold has been found in Maryland, Pennsylvania, and Vermont, on the range of the Appalachian chain, it has proved insufficient to justify mining explorations, except over a limited area in Vermont during the year 1859. The veins of the southern gold region are found in various rocks of a granitic character, and in the horn-blendic rock called diorite, all of which are often in a decomposed condition to the depth of 200 ft. or more.
They are also met with in a variety of slates, as talcose, micaceous, chlo-ritic, and hornblendic. In North Carolina a belt of such crystalline slates several miles wide is traced through several counties on the E. side of another belt of granite and W. of one of hornblendic rock, in all of which the veins are found. In South Carolina the geognostical relations of the gold are very similar. Steatitic strata are met with near the mines, and dikes of intrusive rocks are often found cutting the veins and sometimes disturbing their regularity. The course of the veins is by no means uniform; they run in various directions, and are often tortuous as well as displaced by faults. Their most common general bearing is N. E. and S. W., with a dip toward the N. W. Veins in which the quartz gangue is highly crystalline commonly abound in iron pyrites; as they are explored, pyritous copper is generally met with at some depth. In most instances the gold diminishes with the increase of copper, and the latter metal not proving abundant enough to pay expenses, the mines are at last abandoned. Gold is said to have been discovered in Cabarrus co. in 1799, but until the early part of the present century the gold region of the southern states attracted no attention.
Gold had been gathered to a small extent in various places along the ranges of hills on the E. side of the Appalachian chain, between the Potomac and the Coosa river of Alabama; but there was no regular market for its sale, and no account was kept of the quantities collected. These were altogether of placer gold. In 1825 a gold vein was discovered by Mr. Barringer in Montgomery co., N. C, and attention was directed to this source, which in some instances proved highly productive; but this branch of mining was afterward most successfully prosecuted in Virginia, the coarse gold disseminated through the white quartz being more conspicuous than in the North Carolina veins. In the more broken country of the Carolinas and Georgia also the deposits of the streams were more attractive. In 1824 native gold began to appear in the mint at Philadelphia, and the receipts increased rapidly, so that in five or six years it constituted the chief portion of the supplies of this metal. Up to 1827 North Carolina had been the only state producing gold in notable quantities, and the aggregate amount from 1804 is estimated at about $110,000. The first mint deposits from South Carolina were $3,500 in 1829, and from Virginia $2,500 in the same year.
The first deposits of Georgia gold were in 1880 to the amount of $212,000. In 1837 the production had become so great that a branch mint was established by the government at Charlotte, N. C, and another at Dahlonega, Lumpkin co., Ga., both of which commenced operations the next year. They were suspended in 1861, but in 1869 that at Charlotte was reestablished as an assay office. "When the discoveries of gold in California were announced, the placer deposits and many of the veins in the south were abandoned. The total amount of southern gold deposited at the mints and assay offices of the United States, from the opening of the mines to June 30, 1873, was $1,631,612 from Virginia, $9,983,585 from North Carolina, $1,378,180 from South Carolina, $7,267,784 from Georgia, $79,018 from Tennessee, and $211,827 from Alabama; total, $20,052,006. Of the deposits in 1873, $2,423 came from Virginia, $120,332 from North Carolina, $160 from South Carolina, $35,437 from Georgia, and $599 from Alabama. - The existence of gold in California had been known from the time of the expedition of Drake, 1577-'9, being particularly noticed by Hakluyt in his account of the region.
The occurrence of gold upon the placers was noticed in a work upon Upper California published in Spain in 1690, by Loyola Cavello, at that time a priest at the mission of San Jose, bay of San Francisco. Capt. Shelvocke in 1721 speaks favorably of the appearance of the soil for gold, and of the probable richness of the country in metals. The "Historico-Geographical Dictionary" of Antonio de Alcedo, 1786-9, positively affirms the abundance of gold, even in lumps of 5 to 8 lbs. The favorable appearance of the country for gold, and of Oregon also, was noticed by Prof. J. D. Dana, and recorded in his geological report of the country. In Hunt's "Merchants' Magazine" for April, 1847, is a very decided statement by Mr. Sloat respecting the richness of the country in gold, made from his observations there the two preceding years; and he confidently predicts that its mineral developments will greatly exceed in richness and variety the most sanguine expectations. In these years the Mormons connected with the army were known to have gathered some gold upon the banks of the streams, and the Mexicans and Indians also.
A party of three Americans, two of them Mormons, were on Feb. 9, 1848, at Sutter's mill on the American fork of the Sacramento, near the town of Coloma in El Dorado co., engaged in repairing the race, which had been damaged by the spring freshets, when the little daughter of the overseer, named Marshall, picked up in the race a lump of gold and showed it to her father as a pretty stone. The discovery did not immediately attract much attention; and the Mormons particularly sought to prevent the facts from being made public. The Rev. 0. S. Lyman, in a letter to the "American Journal of Science," of March, 1848, says: "Gold has been found recently on the Sacramento near Sutter's fort. It occurs in small masses in the sands of a new mill race, and is said to promise well." The news spread rapidly, and caused an unparalleled tide of emigration to pour in from Mexico, South America, the Atlantic states, and even from Europe and China. (See California.) In August of that year Governor Mason reported 4,000 men engaged in working gold, and a daily product of the value of $30,000 to $50,000. The earlier diggings were mostly deposits resting upon the upturned edges of argillaceous slates, the gold being found entangled in these under the sand and gravel, and also more or less mixed through the superficial layers.
A large proportion was picked out by hand at many of the diggings, so abundant were the coarse pieces. Attention was early directed to the gold veins, and in 1851 regular quartz mining was commenced at Spring Hill in Amador co. In 1857 numerous mills, most complete and thorough in their construction, were in operation over a great part of the country; and mines were opened at greater depths than gold is often worked in other countries. A shaft of the Mount Hope mining company in Grass Valley was carried to the depth of 241 ft., reaching the vein at 350 ft, following its slope, and the richness of the veinstone at this depth gave full encouragement to the belief that these repositories were permanent and inexhaustible. Many other mines were worked from 150 to 200 ft. in depth. In California, though gold is found E. of the Sierra Nevada, among the mountains of the coast, and in various other localities, the great gold region is on the W. slope of the Sierra, and extends from about lat. 35° N. northerly to Oregon, a distance of about 500 m. The average breadth of this gold belt is about 40 m.
The principal mining operations have been confined to a central area extending N. and S. about 220 m., between the parallels of 37° and 40°, and embracing Mariposa, Tuolumne, Calaveras, Amador, El Dorado, Placer, Nevada, Sierra, Yuba, Butte, and Plumas counties. According to William P. Blake, gold-bearing veins on the W. slope of the Sierra Nevada occur in or are closely associated with clay states, sandstones, and conglomerates of the secondary period; also in hard and compact granite, in greenstone or dioritic rocks, and in dolomite and metamorphic limestones. In the Coast mountains they are found even in the partially metamorphosed stratified formations of the cretaceous period. The largest and most extensive veins exist in the region of the metamorphosed secondary rocks, varying in width from a few inches to 20 or 30 ft., and generally conforming to the dip and strike of the strata. " The most extensive vein of the state," savs Mr. Blake, " and perhaps in the world, is known among the miners as the 'mother vein,' and extends, but with some considerable breaks and interruptions, from Mariposa northwestward for 80 or 100 m., following a zone or belt of Jurassic slates and sandstones, and closely associated with a stratum of dolomite or magnesian rock, often a magnesite, filled with reticulations of quartz veins and charged with pyrites." The chief production of California gold has been obtained from placers.
The great placer region extends over the central counties from Mariposa to Butte. The deposits occur not only in the beds of the streams, but also upon the hillsides and tops, where ancient watercourses are supposed to have been. Sometimes they are found under enormous accumulations of sand, clay, gravel, and even of tufa and lava; the smoothly worn stones are thoroughly cemented together, and form a solid conglomerate or "cement;" the auriferous deposits consist of gravel and bowlders, varying in size from a grain of wheat to masses weighing many tons. These hills on the W. slope of the Sierra Nevada cover a tract of country in places 50 to GO m. in width, and rise sometimes to the height of 4,000 ft. They are traversed by numerous streams, whoso sources are in the Sierra Nevada. Subject to sudden and extreme freshets from the melting of the snows and from the long continued rains of the wet season, these streams excavate and sweep down the loosely aggregated rocks, and wear deep canons and gulches, which extend toward the valleys of the Sacramento and San Joaquin. Thus it was the same agency which impressed this peculiar feature upon the topography of the region, and spread the gold from the veins in the hills through the ravines and down into the valleys.
Even upon the elevated plains quite to the west of the hills gold is collected in strata of sand and clayey deposits, which cover the surface to the depth of 15 to SO ft. or more. The clay is often seen to be but partially decomposed slate, still retaining the structure of this rock, which was evidently the matrix of the gold. - The general gold formation of California is found in the neighboring states and territories, the entire territories of the United States west of the Rocky mountains being more or less productive. In many parts of this region valuable mines are already worked, and there is little doubt that some of them may in the future contribute more than California to the general gold production of the country. In Nevada gold has been obtained from the quartz and from placers, but the product of the state has been chiefly derived from the auriferous silver ores of the great Comstock vein, discovered in 1859, which yields about one third gold and two thirds silver. Gold has been obtained from Oregon since 1850, and the recent production has been roughly estimated at about $2,000,000 annually.
It was first discovered in Washington territory on the E. slope of the Cascade mountains in 1858. The gold region was traced along the upper Columbia and its tributaries, and in 1860 it was found on the W. slope of the Bitter Root mountains, now in Idaho. There are gold washings in almost all parts of Idaho; the gold contains more silver than that of California, and averages about .760. In Montana there are extensive placers and quartz veins, on the E. slopes of the Bitter Root mountains, and on both sides of the Rocky mountain chain, at the sources of the Missouri river. In Colorado gold occurs in lodes or fissure veins, in a belt about 50 m. wide, extending over the central portion of the territory N. and S. (See Colorado.) Gold is also obtained from Utah and Arizona, and is known to exist in Dakota. The auriferous belt of Oregon, and of Idaho, Montana, and Washington territories, extends N. along the slopes of the Rocky mountain chain into British Columbia. The mining of gold in this latter country dates from 1858, though the existence of the metal had been announced in 1856. Gold has been found on the Eraser river from a point about 45 m. from its mouth to its source in the Rocky mountains, a distance of upward of 700 m. by the meanderings of the river.
It is also found on many tributaries of the Fraser and on Vancouver island. The fields which have been most extensively worked are in the Caribou district, which lies in the X. bend of the Fraser. N. of this district placers have been discovered on Peace river, and still further N. on the Stickeen, which empties into the Pacific S. of Sitka, near lat. 55°. The metal has also been found above that point, but in small quantities. The greater part of the gold from British Columbia is obtained from shallow placers. The production is sent to San Francisco; it amounted in 1873 to $1,250,035. (See British Columbia.) - In the province of Ontario, Canada, gold has been found in small irregular deposits of considerable richness in Madoc. The gangue of the gold was in part a ferriferous bitter spar, and in part a peculiar hydrocarbonaceous coaly matter, the two being associated in the same veins, and alike penetrated by crystalline gold of great purity. The adjacent township of Marmora has since been found to contain gold in quartz veins with mispickel. Though not rich, the ore is abundant, and the deposits there are now worked on a considerable scale.
The rocks of this region are crystalline schists, probably of Huronian age; and rich gold-bearing veins have recently been discovered in rocks of the same period N. of Lake Superior, on Lake Shebandowan. For many years the gold-bearing alluvions of the Chaudiere and the adjacent region in the province of Quebec have attracted attention, and have yielded more or less gold. It is distributed over a large area, but the official returns in 1869 show a production of only 1,050 oz. from the Chaudiere valley, although small quantities are extracted in various other localities in the region. The source of the gold appears to be in part in the adjacent crystalline rocks of Huronian age, and in part in some argillites and sandstones which are perhaps of the lower Cambrian period, but may be more recent. In both of these formations, native gold accompanied with sul-phurets occurs in quartz veins, which have not however as yet been systematically worked. In Nova Scotia the auriferous quartz occurs in uncrystalline slates and sandstones, for the most part in interbedded veins. The workings have been on a small scale and very irregular, but the quartz is often of great richness.
The official returns from 1860 to 1872 show a yield of 215,871 oz., with a value of £863,484. The produce in 1867 was 27,314 oz., but in 1872 only 13,094 oz. - The gold-producing districts of South America are in Brazil, Chili, and all. those countries which lie north of the latter on the line of the Andes. As in Europe and Asia, it is the N. and S. ranges of hills of micaceous and talcose slates, quartz rocks, and granites, which produce this metal. In some instances, as in Peru and Chili, it is obtained from veins commonly worked for other metals as well as gold; but almost universally it is a product of alluvial mines. The yield since the early working of the mines has greatly fallen off, and especially since the commencement of the present century; and South America, from having been the first of the gold-producing countries in the world, has now fallen among those of least importance in this respect. Still it is well known that there are districts of great richness yet comparatively unworked, and which are likely long to continue so from their extreme un-healthiness and the want of means of comfortable subsistence.
Such is the country about the head waters of the Atrato, the Magdalen a, and the Cauca. Similar causes, as well as the political condition of the countries of Central America, have prevented the development of their resources in this metal, which it is well known follows the Cordilleras northward. On the isthmus of Panama discoveries of images of gold in the graves of the aborigines point to the existence of productive mines in Chiriqui, the localities of which are not now known. The gold is very generally alloyed with copper; some of it indeed is only 8-carat gold, while in other samples the proportion is 23 carats. The gold of Mexico has been rather a secondary product of its argentiferous veins; but in Oajaca are true gold veins in the micaceous slates and gneiss. The silver ores which contain the gold are often argentiferous galena, the lead being the prevailing metal. A small quantity of gold is annually obtained from Central America, and gold placers are known to exist in Cuba and Santo Domingo. Although gold has been found in many places in Brazil, the most productive mines have been worked in the province of Minas Geraes in the vicinity of Ouro Preto, and in the district of Turyassu, in the province of Maranhao. The large production of Brazilian gold in the 18th century was obtained almost exclusively from the alluvial washings of Minas Geraes; but these became exhausted, and the metal is now obtained from the veins or beds worked by English capital.
The gold found in Brazil, instead of being enclosed in regular veins, is disseminated in metalliferous beds. The rock formations are supposed to belong to the pa-laeozoic period. - The total production of gold in the world has never been determined with more than an approximate degree of accuracy. There are no statistics showing the exact annual yield of the different gold-producing countries, and the amount produced has been subject to computations by different authorities, whose results have presented no little variance. It is true that in each country an accurate record is kept of the amount coined, and of the exports and imports, but these results only indicate approximately the extent of the production. In 1830 it was estimated that for the preceding 19 years the average annual production of the precious metals had fallen off about $31,000,000 from what it had been before that time, the estimated product being as follows:
Europe and Asia................
By the estimate of M. Chevalier, in his work on money, the total amount of gold and silver existing in various forms in 1848 appears to have been £1,727,000,000, or $8,500,000,000, of which one third was supposed to be gold. The annual product of this metal from 1800 to 1850 had been £3,258,000. By other authorities the whole amount of gold coin and bullion in Europe in 1847 was estimated to be about £250,000,000, and in the world in 1850 £600,-000,000. According to Phillips, the annual production at the beginning of the century was about 53,040 lbs. troy, of which New Granada furnished 23 per cent., Brazil and southern Asia 18 per cent. each, Chili 13, Mexico 8, Austria 6, and Peru 4 per cent. In 18G0 the production had increased to 585,370 lbs. troy, of which the chief countries contributed in the following ratio per cent.: Australia, 37; California and neighboring states and territories, 31.9; Russia, 11.3. In 1865 the yield amounted to 559,587 lbs. troy, of which 37.5 per cent. was the product of California and the neighboring states and territories, 27.9 of Australia, and 12.4 of Russia. The following approximate statement of the value of the gold produced in the principal gold-producing countries in 1867 is given by Blake in his "Production of the Precious Metals:"
Ratio per cent.
Oregon and Washington..............
Utah, Appalachians, and other sources.
Total United States..............
Canada and Nova Scotia........
Venezuela, Colombia, Central America, Cuba, and Santo Domingo.........
Borneo and East Indies.. ........
China, Japan, Central Asia, Roumania, and other unenumerated sources..
The production of Australia above given is thus distributed by Blake : "Victoria, $20,510,-000; New South Wales, $4,500,000; Queensland, $400,000; South Australia, $140,000. Since about 1850, by for the greater portion of all the gold obtained in the world has been the product of the Australian mines and those on the Pacific coast of the United States. The extent of the Australian production is indicated by the following table, from the official "Statistical Abstract of the several Colonial and other Possessions of the United Kingdom," giving the value of the exports of bullion and coin from New South Wales and Victoria, from the opening of the mines. It should be observed, however, that it does not represent the exact production of each colony. The coin was issued from the branch of the royal mint at Sydney, New South Wales. A branch mint wa9 established at Melbourne, Victoria, in 1872.
NEW SOUTH WALES.
Exclusive of coin.
Exclusive of coin.
The exports from New Zealand began in 1857, and to the beginning of 1872 had amounted to £24,492,149. They increased from £40,084 in 1857 to £2,897,412 in 1866, then gradually decreased till 1870, when they amounted to £2,103,910, but in 1871 increased again to £2,788,308. The accurate determination of the amount of gold produced in the United States since the discovery of this metal in California is not practicable. As J. Ross Browne, W. P. Blake, R. TV. Raymond, and others have shown, neither the manifests of export, nor the mint receipts, nor the bullion shipments of the express companies, nor any direct combination of these data, will give the required amount. This is particularly the case with regard to earlier years. The following table, compiled by R. W. Raymond, United States commissioner of mining statistics, is offered as an approximate estimate, the result of careful study of numerous treatises and partial statistics, in the light of much personal observation of the principal producing districts.
Down to 1862 it follows the table compiled by J. Arthur Phillips, and published in his "Gold and Silver." From 1862 to 1866 the production of California is calculated by deducting from the express receipts of uncoined treasure at San Francisco, from " the northern and southern mines," the receipts from Nevada, and adding 10 per cent. to the remainder, to cover amount shipped in private hands. From 1866 to 1872 inclusive the reports of the United States mining commissioner have been followed as a general authority; but as these do not separate the product of gold from that of silver, the division has been made by estimate, based on the known conditions and relations of the industry of different localities. The figures for 1873 are based on the express shipments, with arbitrary allowances for product otherwise transported. Under the head of "Other States and Territories" is included the product of gold from Oregon, Washington, Idaho, Montana, Colorado, etc, and one third the product of the Comstock lode in Nevada, that being the average proportion of gold by value in the Corn-stock bullion.
The values are given in United States gold coin.
• and territories.
55 000 000
55 000 000
50 000 000
43 000 000
40 000 000
53 225 000
51 725 000
48 000 000
40 500 000
36 000 000
Other authorities have made the production of California in recent years somewhat larger, as will appear by reference to the article California. - It is estimated that about three fourths of the gold produced is used for coinage, and about one fourth in the arts. Thus, estimating the entire product of the world in 1873 at $100,000,000, it is supposed that the consumption in the arts, which has greatly increased in recent years, approximated $25,-000,000. There has also been a recent increasing demand for gold for coinage, attributed to the fact that several countries which formerly used gold and silver as the double or alternate standard of value, have reformed their monetary laws, and adopted the gold standard, that metal being less variable than silver. Among the countries which have recently made this change are the United States, Germany, Denmark, Sweden and Norway, and Japan. Great Britain adopted the gold standard in 1816. France, Belgium, Italy, Switzerland, and Greece still adhere to the double standard.
The total gold coinage of the world from 1848 to 1872 has been stated in round numbers at £602,116,-000. Of this amount France coined £259,801,-000, the United States £185,579,000, England £123,608,000, and Australia £32,128,000. According to the latest report of the director of the mint, the entire gold coinage of the United States to June 30, 1873, amounted to $816,-905,878, in addition to $285,358,663 manufactured into bars, making the total issue from the mints and assay offices $1,102,264,541. (See Coins.) Of this amount coinage to the value of $35,249,337 and bars valued at $20,495,616 were issued during the year ending June 30, 1873. The amount of gold of domestic production, exclusive of coins, deposited at the various mints and assay offices of the United States from their establishment to June 30, 1873, with the sources of production, has been as follows:
$71, 662 41
Parted from silver......
Contained in silver......
The localities given in this table are merely those from which the mint deposits were declared or inferred to come; hence they do not represent correctly the actual origin of production. A considerable amount, for example, is attributed to Kansas, which really produces no gold. The gold coinage of Great Britain and Australia for 10 years has been as follows:
The exports of domestic gold from the United States during the year ending Dec. 31, 1873, amounted to $55,178,229 in coin, and $12,754,-257 in bullion. - Gold Mining. Gold occurs principally in metallic form, as threads, scales, spangles, films, grains, monometric crystals, nuggets, etc. Such native gold always contains from 1 to 40 per cent. silver, and often also small quantities of iron, copper, mercury, palladium, platinum, or iridium. Gold ores proper are rare; the undoubted species are tellurides. More commonly gold occurs associated with other minerals, chiefly (in decomposed ores) the oxides of iron, and (in solid ores) iron and copper pyrites, galena, blende, mispickel (all of which may be auriferous), bismuth, stib-nite, magnetite, hematite, various spars, and quartz. It is believed by many that auriferous pyrites often contains its gold in chemical combination with antimony, arsenic, or sulphur; but this is probably not the case with all pyrites, or with all the gold in any variety of pyrites. Gold is classified further as quartz gold (found in veins, &c), and wash gold (found in placers, gravel and cement deposits, &c). The methods of extraction are mechanical, chemical, or both, according to circumstances. Mechanical methods involve the agency of air or water.
Air separation is the rude process of winnowing, occasionally practised in localities where water is wanting. The dry pulverized material is repeatedly thrown into the air, allowing the wind to carry off the lighter portions, the remainder being caught as it falls in a hide or blanket, or a shallow wooden basin called a batea. The process is concluded by blowing the last residuum with the mouth. Washing-is the almost universal method of mechanical separation. In exploring for gold, the earth or pulverized rock suspected to contain it is washed on the blade of a shovel, or in an iron pan, wooden batea, or horn scoop. The operation is commonly called panning. It consists essentially in stirring and shaking under water the contents of the vessels employed in such a way as to suspend the finer earthy particles and allow them to escape over the edge, while the gold, with the larger stones or lumps of clay, remains behind. The stones are removed with the fingers, and the lumps of clay are rubbed between the hands and reduced to a slime, the process being skilfully continued until nothing is left except gold and heavy black sand, usually titaniferous iron, which accompanies native gold in most localities and cannot be separated by washing.
When perfectly dry, a part of it can be removed by blowing and a part by the magnet. It is common to melt the finer dust with fluxes and collect it in buttons. Quicksilver may also be introduced in panning, to take up and secure the fine gold. The cradle, or rocker, is an apparatus somewhat resembling a child's cradle. The box is usually about 40 in. long and 20 wide, and from 15 in. to 2 ft. high at the upper end, upon which is set a hopper or riddle, a box 20 in. square and 6 in. deep, having a bottom of sheet iron perforated with half-inch holes. Under the riddle is placed an inclined apron of canvas, and across the bottom of the main box are nailed two bars or riffles, about three fourths of an inch high. In washing, the dirt is shovelled into the hopper, and the workman ladles water upon it with one hand, rocking the cradle with the other. The sheet-iron bottom retains the larger stones; the disintegrated earth, passing through the riddle, falls upon the apron, which carries it to the head of the cradle box, whence it flows along the bottom and escapes at the lower end, leaving behind the riffle bars the gold, black sand, and heavier particles of gravel, which are cleaned up two or three times a day.
This apparatus is both slow and wasteful in operation; but it is cheap and portable, and requires little water, since the same water can be used in it over and over again. The long torn is a wooden trough, about 12 ft. long, 20 in. wide at its upper end, and 30 in. at the other. It terminates below with an inclined riddle of punched sheet iron, through which the material is carried by a stream of water entering at the other end, and falls upon a riffle box below. A fresh supply of dirt is continually shovelled in at the head of the trough. This arrangement works faster than the rocker, and is not so liable to become packed with sand; but the sluice, which has now generally superseded it, is capable of washing still greater quantities and with less loss of gold. This is generally a long inclined wooden trough, into which the dirt is shovelled, and through which a rapid stream of water continually flows. The ordinary sluice is a series of rough wooden boxes, each 12 ft. long, 16 by 20 in. wide, and 10 in. to a foot deep. The grade is commonly 10 to 18 in. on each box. False bottoms are employed to retain the gold and prevent the wearing out of the boxes. Sluices are sometimes paved with stones or wooden blocks, in the crevices of which the gold is caught and retained.
Riffles are also inserted, and quicksilver is very generally employed to assist in catching the gold. The dirt or gravel containing gold is shovelled into the sluices at the head of the series. Mercury is usually poured, an hour or two after the commencement of sluicing, into the head of the apparatus, and smaller quantities are also introduced at various places along the boxes. When the gold is exceedingly fine, amalgamated copper plates are sometimes set in the sluices, and are considered as effective for saving tine gold as an equal surface of pure mercury, while they are both cheaper and more easily managed. Another arrangement for obtaining fine gold consists in allowing a current carrying suspended gold, sand, etc., to pass over tanned hides, laid with the hairs directed against the course of the stream, or over rough baize or blanket, such as is now manufactured for the purpose in California. The blankets are frequently removed and washed in tanks. Where skins are used, as in Brazil, they may be dried and beaten over a cloth, placed to receive the fallen particles. Sluice washing is generally carried on during the day only; but when water is abundant and cheap, the work may be continued throughout the whole twenty-four hours.
The sluices are cleaned up once a week, or more seldom, according to the rate at which gold and amalgam accumulate. The amalgam and mercury taken from the sluice are panned, to separate them from sand, etc., and then strained through buckskin or canvas to remove the liquid quick-silver. The auriferous amalgam is removed from copper plates by first warming and then scraping them. This, together with the solid amalgam from the strainers, is retorted; the quicksilver passing over from the retort is condensed in water and thus recovered; while the gold is left in the form of a light yellow porous mass, called retort gold, and usually constituting 35 to 40 per cent. of the weight of amalgam retorted. The length of the sluices employed in this process is limited only by the cost of their construction and maintenance, and the control of the necessary grade. Ground sluices are natural gullies, answering the purpose of wooden sluices in localities where water is abundant for short periods only, and the construction of permanent sluices would not be judicious. In river mining, the current of a stream is turned aside, and sluices are erected in its bed for washing the dirt there accumulated.
In beach mining, as carried on along the northern part of the California coast and the southern part of the Oregon coast, the sands on the seashore are explored, and certain portions of them, which are found to be sufficiently auriferous, are transported to some neighboring stream and washed. The origin of this gold is the natural concentration by tides and currents of a bluff of auriferous sand, which in stormy weather is undermined by the waves. The position of the deposits is frequently changed, and mining must therefore be carried on in a new place every day. - Hill diggings and bank diggings are names which explain themselves. Many deposits of auriferous clay and gravel have been subsequently overlaid by barren alluvium; and the ordinary operations of shovelling or blasting would be too expensive for the removal of such enormous masses of unprofitable material. Tunnels and drifts are frequently employed for the purpose of extracting the richer strata. They are particularly necessary in those deep placers in which the drift materials are united by sili-cious or calcareous matter, constituting a hard, solid cement. This material is usually mined by drifting, and, if too hard for sluicing, is subjected to a treatment similar to that employed for quartz gold.
Water for sluicing operations is frequently brought from great distances through canals, ditches, or flumes, the proprietors of which sell the water to miners at so much the miners1 inch, a miners' inch being in most localities the quantity flowing in a given time through an aperture one inch square under a head of six inches. - The celebrated hydraulic process, invented in Placer co., Cal., in 1852, consists in washing down the whole surface and underlying mass of auriferous deposits, preparatory to sluicing. This is effected by streams of water under great hydraulic pressure. The first apparatus of the kind had a head of 40 ft. From a barrel situated this distance above the mining claim the water was drawn through a hose 6 in. in diameter, made of common cowhide and ending in a four-foot tin tube, the nozzle of which was one inch in diameter. From this simple beginning has grown in 20 years one of the most remarkable mechanical industries of mining. Hundreds of miles of ditches, canals, and flumes are now employed in conducting water for these operations from the high streams of the Sierra; canvas and iron hose have replaced the original cowhide; blasts of from 5 to 50 tons of powder at a time are fired, to prepare the ground for the action of water; nitro-glycerine and the diamond drill are used in running preparatory tunnels for drainage; chasms of 1,000 ft. in vertical depth are successfully crossed by huge iron pipes, to convey water to isolated points, thus obviating the ancient high, costly, and perishable flumes; and from ingeniously contrived and regulated nozzles streams as much as 6 in. in diameter are discharged under pressures sometimes exceeding 400 ft. of hydraulic head, with a velocity of 140 ft. and upward per second, delivering more than 1,600 lbs. of water in that unit of time.
The water issuing from the nozzle seems to the touch as rigid as a bar of steel, and strikes the gravel bank in the same cylindrical, condensed shape, boring into it with immense power. The heavy bowlders are thrown about like pebbles; and the clay, earth, and gravel, disintegrated by the torrent, are swept along into the system of sluices. It has been estimated that, taking the miners' wages in California at $4 per day, the cost of handling a cubic yard of gravel would be nearly as follows: in the pan, $20; in the rocker, $5; with the long torn, $1; by hydraulic process and sluices, 5 cts. This method has rendered valuable many California placers that were esteemed worthless or exhausted; and its employment would doubtless revive the importance of abandoned gold fields in other parts of the world. - Quartz gold (that is, gold contained in veins, whether native in the quartzose or other gangue, or associated more or less intimately with metalliferous minerals) is extracted in most cases by first pulverizing the material, and then washing and amalgamating. Stamp mills, iron rollers, revolving plates, drums containing iron balls, Chilian mills, arrastras, and jaw crushers are among the machines employed in pulverizing rock.
The arrastra consists of a circular pavement of stone, about 12 ft. in diameter, surrounded by a rough curb and forming a kind of tub about 2 ft. in depth. An upright shaft, working on a pivot in the centre of this circle, carries arms to which large stones or mullers are attached by chains or thongs. The arms, being revolved by horse or mule power, drag the mullers over the pavement, upon which the ore, previously broken into pieces of about the size of pigeons' eggs, is distributed. Water is added from time to time, until the quartz has become reduced to a finely divided state, and the contents of the arrastra assume the consistency of thick cream. Quicksilver is then sprinkled over the surface, and the grinding is continued until amalgamation is complete. An ordinary twelve-foot arrastra will grind and amalgamate 450 lbs. of quartz in about seven or eight hours. The amalgam is obtained by diluting and agitating the mixture, and allowing the turbid liquid to run off. The arrastra is slow in operation and wasteful of power, but an excellent amalgamator. Hence the principle has been very generally adopted in amalgamating, while the preliminary pulverization is effected by other machinery.
The Chilian mill consists of a stone or iron basin, around which one or two vertical wheels or runners, frequently of granite, are made to travel. It is generally considered less efficient for amalgamation and scarcely more so for crushing, while it is more expensive to construct than the arrastra. Jaw crushers, of which Blake's well known stone breaker is the type, are widely employed for the preliminary reduction of rock to a size suitable for rollers or stamp mills. Stamping is usually regarded as the most economical and efficient means of pulverizing the ore. The mills constructed for this purpose are run by steam or water power, with the exception of occasional rude contrivances in which single stamps have been operated by horse power, and of the experiment now making, it is believed for the first time, in the island of Arruba, where wind is to be employed as a motive power. The best stamp mills in the world are believed to be those of California and Nevada. These are made up of batteries containing three, four, five, or six stamps each; five is the usual number. Each battery works in a cast-iron box or mortar, in the bottom of which are laid blocks of hardened iron, called dies, to receive the shock of the falling stamps.
The broken rock is fed in suitable quantities into the mortar, and crushed between the dies and the stamps. Each stamp consists of a stem, a collar, a stamp head, and a shoe. The stem was formerly made of ash or other hard straight-grained wood, about 6 in. square, to the lower end of which a square iron stamp head was fastened. At present, in California, stems of 3 or 3 1/2 inch round iron, some 12 ft. in length, are universally employed. The collar is secured upon the upper part of the stem, and forms a projection 3 or 4 in. wide, under which the cam of the horizontal driving shaft catches and lifts, and at the same time turns, the stamp. The stem fits below into the stamp head, a cylinder of tough cast iron, furnished on its lower face with a hard iron shoe, which can be replaced when worn out. The stamps are dropped 6 to 12 in., at the rate of from 25 to 90 drops per minute. Water flows into the mortar with the ore; and the finely divided product is splashed by the stamps through screens of wire cloth or perforated sheet iron, set in the walls of the mortar. Loose quicksilver and amalgamated copper plates are sometimes used inside the mortar. The mixture of crushed ore and water is differently treated in different places for the extraction of gold.
Sometimes it is run over amalgamated copper plates; sometimes it is first concentrated by means of blankets; sometimes it is introduced into pans, somewhat on the principle of the arrastra, or into various other ingenious forms of apparatus, for the purpose of amalgamation. In the most suecessful establishments, the current conveying the sediments is led through a succession of apparatus, each machine, sluice, or other contrivance being intended to catch a portion of the gold carried past the preceding one. The refuse finally escaping is called tailings, and usually contains : native gold, so finely divided that it has been swept by the current through all the apparatus employed; minute particles of amalgam and "floured" quicksilver, carried off in the same way; coarser particles of gold adhering to fragments of rock; and, finally, gold associated mechanically or chemically with iron or copper pyrites, blende, galena, and mispickel. The tailings are usually run into reservoirs, allowed to settle, and then stored in heaps. Sometimes these heaps are again amalgamated, with or without a preceding concentration by washing. It has been found in many instances that some kinds of pyrites slowly decompose by exposure and thus set free fine gold.
The metallic sulphu-rets are, however, in many cases, separated from other tailings by washing immediately after the first amalgamation of the ore, and various devices have been employed for the treatment of such concentrated pyrites, which is often the richest in gold of all the constituents of the vein stuff. Following the analogy of natural decomposition, it has been repeatedly attempted, by roasting the pyrites in reverber-atory furnaces, to drive off the sulphur and oxidize the metallic bases, so as to obtain a product containing fine particles of free gold. The objection brought against this treatment, that the vapors of roasting carry off mechanically fine particles of gold, seems to be ill-founded. More serious objections are the cost of the roasting process, and the circumstance that the roasted product does not contain the gold in a condition suitable for amalgamation. It is supposed that the particles when thus artificially and rapidly reduced become coated with a film of oxide of iron, preventing the intimate contact with quicksilver upon which amalgamation depends.
Very careful roasting in cylinders, with the addition of salt, is said to have obviated this difficulty; but the question of expense remains. - The present methods of treatment for pyritous gold ores are: 1, the extremely fine pulverization of the ore, liberating, as far as this is mechanically possible, the particles of gold; 2, the amalgamation of the pyritous residues in pans, with the addition of chemicals intended to facilitate decomposition; 3, chlorination; 4, smelting. The chlorination process was introduced by Prof. Plattner of Freiberg, Saxony, for the treatment of auriferous residues in Silesia. As improved by Deetken, it has been employed in this country for about 15 years. The principle involved is the transformation of metallic gold by means of chlorine gas into soluble chloride of gold (the aurum potabile of the alchemists), which can be dissolved in cold water and precipitated in the metallic state by sulphate of iron. This precipitate may then be filtered, dried, and melted with suitable fluxes, to obtain a regulus of malleable gold. It is necessary that all the gold, and if possible nothing else, shall be obtained in the final solution. If this is secured, the precipitation and melting are easy.
To render the gold in the ore accessible in a metallic state to the chlorine gas, and at the same time to convert the base metals into oxides which will not unite with the chlorine, the raw ore is finely pulverized and (if sulphurets or arseniurets are present) roasted. The cost of this treatment, amounting in the Pacific states and territories to from $12 to $25 a ton, excludes its use for low grade ores; and hence it cannot supersede the stamp mill and amalgamation process, though it is acknowledged to be metallurgi-cally the most complete method of gold extraction on a large scale. Ores containing iron, copper, gold, and silver may be roasted and deprived of their copper and iron by leaching with dilute sulphuric acid, of their silver by boiling with concentrated sulphuric acid, and of their gold by treating the auriferous residuum with aqua regia. If lead is present, the whole residuum after the removal of copper must be melted with lead and cupelled. This process is not now used in the United States, though it is recommended by high authority. Telluric ores are treated in Transylvania in a somewhat similar way. The smelting processes for the extraction of gold are the same as those for silver.
Since the two minerals always occur in nature together, the final result of smelting is argentiferous gold or auriferous silver. The separation of the two metals is effected : 1, by dissolving the silver in nitric acid or boiling sulphuric acid, which leaves behind a brown powder of gold; 2, by treating the alloy with aqua regia, in which gold is dissolved as chloride, while the chloride of silver is but slightly soluble; or 3, by passing a current of chlorine gas through the alloy while in a melted state. For separation with nitric acid, the alloy should contain 2 1/2 parts of silver to 1 part of gold. For the separation with sulphuric acid, the best results are obtained with alloys containing not much less than 3 or more than 4 parts of gold in 16 parts, the remainder being silver and copper. It is usually necessary in treating native gold to melt it with at least 2 1/2 times its own weight of silver, and then to separate by the action of acids the silver thus added, and also that originally contained in the gold. It is said that the chlorine process effects a complete separation of the silver in one operation, at the time the gold is melted, and thus saves much time, material, machinery, and interest on capital.
Nitric acid and sulphuric acid processes are used in the mints of the United States, and the chlorine process is employed in some of the British colonial mints. - Among the most recent authorities on this subject are : Phillips, "The Mining and Metallurgy of Gold and Silver"
(London, 1867); J. Ross Browne, "Mineral Resources of the Pacific Slope" (New York, 1808); Blake, "Production of the Precious Metals" (New York, 1869); R. W. Raymond, "Silver and Gold" (New York, 1873). See also Sel-wyn's "Notes on the Physical Geography, Geology, and Mineralogy of Victoria" (Melbourne, 1866), and the reports on the geology of California by J. I). Whitney.