GOLD—WHAT IT IS AND WHERE IT COMES FROM.
Road-mending is pretty general at this time of the year, and upon roads now being newly macadamized we may pick up a good many differing specimens of granite. On the newly-broken surface of one of them, four substances of which it is composed can be perceived with great distinctness. The more earthy-looking rock, in which the others seem to be embedded, is called felspar; the little hard white stones are bits of quartz; the dark specks are specks of hornblende, and the shining scales are mica. Felspar, quartz, hornblende, and mica are the four constituents of granite. These are among the rocks of the most ancient times, which form a complete barrier to the power of the geologist in turning back the pages which relate the story of our globe. Layer under layer—leaf behind leaf—we find printed the characters of life in all past ages, till at last we come to rocks—greenstone, porphyry, quartz, granite, and others—which contain no trace of life; which do not show, as rocks above them do, that they have been deposited by water; but which have a crystalline form, and set our minds to think of heat and pressure. These lowest rocks are frequently called "igneous," in contradistinction to the stratified rocks nearer the surface, which have been obviously deposited under water. Between the two there is not an abrupt transition; for above the igneous, and below the aqueous, are rocks which belong to the set above them, insomuch as they are stratified; while they belong to the set below them—insomuch as they are crystalline, contain no traces of life, and lead us by their characters to think of heat and pressure. These rocks, on account of their equivocal position, are called metamorphic.
Under the influence of air, combined with that of water—water potent in streams, lakes, and seas, but not less potent as a vapor in our atmosphere, when aided by alternations in the temperature—granite decomposes. We noticed that one of the constituents of granite—felspar—was a comparatively earthy-looking mass, in which the other matters seemed to be embedded. In the decomposition of granite, this felspar is the first thing to give way; it becomes friable, and rains or rivers wash it down. Capital soil it makes. When the constituents of granite part in this way, quartz is the heaviest, and settles. Felspar and the others may run with the stream, more or less; quartz is not moved so easily. Now, as our neighbors in America would put it, "that's a fact;" and it concerns our gossip about gold.
Below the oldest rocks there lie hidden the sources of that volcanic action which is not yet very correctly understood. Fortunately, we are not now called upon for any explanation of it: it is enough for us that such a force exists; and thrusting below, forces granite and such rocks (which ought to lie quite at the bottom), through a rent made in the upper layers, and still up into the air, until, in some places, they form the summit of considerable mountains. Such changes are not often, if ever, the results of a single, mighty heave, which generates a great catastrophe upon the surface of the earth; they are the products of a force constantly applied through ages in a given manner. In all geologic reasoning we are apt to err grossly when we leave out of our calculation the important element of time. These lower rocks, then—these greenstones, porphyries and granites, sienites and serpentines—thrust themselves in many places through the upper strata of the earth's crust, in such a way as to form mountain ranges. Now, it is a fact, that wherever the oldest of the aqueous deposits—such as those called clay-slates, limestones, and greywacke sandstones—happen to be superficial, so as to be broken through by pressure from below, and intruded upon by the igneous rocks (especially if the said igneous rocks form ranges tending at all from north to south), there gold may be looked for. Gold, it is true, may be found combined with much newer formations; but it is under the peculiar circumstances just now mentioned that gold may be expected to be found in any great and valuable store.
In Australia, the gold discoveries, so new and surprising to the public, are not new to the scientific world. More than two years ago, in an "Essay on the Distribution of Gold Ore," read before the British Association, to which our readers will be indebted for some of the facts contained in the present gossip, Sir Roderick Murchison "reminded his geological auditors that, in considering the composition of the chief, or eastern ridge of Australia, and its direction from north to south, he had foretold (as well as Colonel Helmersen, of the Russian Imperial Mines) that gold would be found in it; and he stated that, in the last year, one gentleman resident in Sydney, who had read what he had written and spoken on this point, had sent him specimens of gold ore found in the Blue Mountains; while, from another source, he had learnt that the parallel north and south ridge in the Adelaide region, which had yielded so much copper, had also given undoubted signs of gold ore. The operation of English laws, by which noble metals lapse to the crown, had induced Sir Roderick Murchison to represent to Her Majesty's Secretary of State that no colonists would bestir themselves in gold-mining, if some clear declaration on the subject were not made; but, as no measures on this head seemed to be in contemplation, he inferred that the government may be of opinion, that the discovery of any notable quantity of gold might derange the stability and regular industry of a great colony, which eventually must depend upon its agricultural products." That was the language used by Sir Roderick Murchison in September, 1849; and in September, 1851, we are all startled by the fact which brings emphatic confirmation of his prophecy.
But it is not only about the Blue Mountains, and in other districts, where the gold is now sought, that the geologic conditions under which gold may be sought reasonably are fulfilled. Take, for example, the Ural Mountains. In very ancient times the Scythian natives supplied gold from thence; and gold was supplied also by European tribes in Germany and elsewhere. Most of those sources were worked out, or forgotten. Russia for centuries possessed the Ural, and forgot its gold. Many of us were boys when that was rediscovered. The mountains had been worked for their iron and copper by German miners, who accidentally hit upon a vein of gold. The solid vein was worked near Ekatrinburg—a process expensive and, comparatively, unproductive, as we shall presently explain. Then gold being discovered accidentally in the superficial drift, the more profitable work commenced. It is only within the last very few years that Russia has discovered gold in another portion of her soil, among the spurs of the Altai Mountains, between the Jena and the Lenisei, and along the shores of Lake Baikal. This district has been enormously productive, and, for about four years before the discovery of gold in California, had been adding largely to the gross amount of that metal annually supplied for the uses of society. The extent of this new district now worked is equal to the whole area of France; but all the gold-bearing land in Russia is not yet by any means discovered. The whole area of country in Russia which fulfills the conditions of a gold-bearing district is immense. Eastward of the Ural Chain it includes a large part of Siberia; and also in Russian America there is nearly equal reason for believing that hereafter gold will be discovered.
Before we quit Asia, we may observe, that the Chinese produce gold out of their soil; and although many of the mountain ranges in that country tend from east to west, yet the conditions of the surface, and the meridional directions of the mountains too, would indicate in China some extensive districts over which gold would probably be found in tolerable abundance. Gold exists also in Lydia and Hindostan.
Now to pass over to America, where, as we have already said, the Russians have a district in which gold may some day be discovered. In many districts along the line of the Rocky Mountains, especially in that part of them which is included in the British territory, gold may be looked for. The gold region of California has been recently discovered. Gold in Mexico, where the conditions are again fulfilled, is not a new discovery. Gold in Central America lies neglected, on account of the sad political condition of the little states there. There is gold to be found, perhaps, in the United States, some distance eastward of the Rocky Mountains. Certainly gold districts will be found about the Alleghanies. Gold has been found in Georgia, North and South Carolina, and Virginia; it exists also in Canada, and may, probably, be found not very far north, on the British side of the St. Lawrence. In the frozen regions, which shut in those straits and bays of the North Pole, to which early adventurers were sent from England on the search for gold, gold districts most probably exist, although the shining matter was not gold which first excited the cupidity of our forefathers. Passing now to South America, New Granada, Peru, Brazil, La Plata, Chili, even Patagonia, contain districts which say, "Look for gold." There are one or two districts in Africa where gold exists; certainly in more districts than that which is called the Gold Coast, between the Niger and Cape Verd; also between Darfur and Abyssinia; and on the Mozambique Coast, opposite Madagascar. In Australia, the full extent of our gold treasure is not yet discovered. In Europe, out of Russia, Hungary supplies yearly one or two hundred thousand pounds worth; there is gold in Transylvania and Bohemia; the Rhine washes gold down into its sands from the crystalline rocks of the high Alps. The Danube, Rhone, and Tagus, yield gold also in small quantities. There are neglected mines of gold in Spain.
To come nearer home. In the mining fields of Leadhills, in Scotland, gold was washed for busily in the time of Queen Elizabeth. It is found also in Glen Turret, in Perthshire, and at Cumberhead, in Lanarkshire. Attempts have been made to turn to account the gold existing in North Wales and Cornwall. About sixty years ago, gold was found accidentally in the bed of streams which run from a mountain on the confines of Wicklow and Wexford, by name, Croghan Kinshela. A good deal of gold was collected by the people, who, having the first pick, had soon earned about ten thousand pounds among them by their findings. Government then established works, and having realized in two years three thousand six hundred and seventy-five pounds by the sale of gold, which it cost them more than that amount to get, they let the matter drop, judiciously.
Let nobody be dazzled, however, by this enumeration of gold districts, which is not by any means complete. It is quite true that there is no metal diffused so widely over the world's surface as gold is, with a single exception, that of iron. But with regard to gold, there is this important fact to be taken into account, that it is not often to be obtained from veins, but is found sprinkled—in many cases sprinkled very sparingly; it is found mixed with quartz and broken rock, or sand and alluvial deposit, often in quantities extremely small, so that the time lost in its separation—even though it be the time of slaves—is of more value than the gold; and so the gold does not repay the labor of extraction. It is only where a gold district does not fall below a certain limit in its richness, that it yields a profit to the laborer. Pure gold in lumps, or grains, or flakes, is to be found only at the surface. Where, as is here and there the case, a vein of it is found deep in connection with the quartz, it is combined with other minerals, from which it can be separated only by an expensive process; so that a gold vein, when found, generally yields less profit than a field. As for gold-hunting in general, the history of every gold district unites to prove that the trade is bad. It is a lottery in which, to be sure, there are some prizes, but there is quite the usual preponderance of blanks.
The villages of gold-seekers about Accra and elsewhere, on the Gold Coast, are the villages of negroes more squalid and wretched than free negroes usually are. The wretchedness of gold-hunters in the rich field of California is by this time a hackneyed theme. Take, now, the picture of a tolerably prosperous gold-seeker in Brazil. He goes into the river with a leathern jacket on, having a leathern bag fastened before him. In his hand he carries a round bowl, of fig-tree wood, about four or five feet in circumference, and one foot deep. He goes into the river at a part where it is not rapid, where it makes a bend, and where it has deep holes. Be pleased to remember that, and do not yet lose sight of what was before said about the heaviness of quartz. The gold-seeker, then, standing in the water, scrapes away with his feet the large stones and the upper layers of sand, and fishes up a bowlful of the older gravel. This he shakes and washes, and removes the upper layer; the gold being the heaviest thing in the bowl, sinks, and when he has got rid of all the other matter, which is after a quarter of an hour's work, or more, he puts into his pouch the residual treasure, which is worth twopence farthing, on an average. He may earn in this way about sevenpence an hour—not bad wages, but, taken in connection with the nature of the work, they do not look exceedingly attractive. Here is a safe income, at any rate—no lottery. A lump of gold, combined with quartz, like that which has been dragged from California by its lucky finder—a lump worth more than three thousand pounds—is not a prize attainable in river washing. That lump, its owner says, he got out of a vein, which vein he comes to Europe to seek aid in working. Veins of quartz containing gold, when they occur, directly they cease to be superficial, cease generally to be very profitable to their owners. But of that we shall have to say more presently.
By this time we have had occasion to observe more than once that gold and quartz are very friendly neighbors. Now, we will make use of the fact which we have been saving up so long, that when granite decomposes, quartz, the heaviest material is least easily carried away, and when carried away is first to be deposited by currents. Gold also, is very heavy; in its lightest compound, it is twelve times heavier than water, and pure gold is nineteen times heavier; gold, therefore, when stirred out of its place by water, will soon settle to the bottom. Very often gold will not be moved at all, nor even quartz; so gold and quartz remain, while substances which formerly existed in their neighborhood are washed away. Or when the whole is swept away together, after the gold has begun sinking, quartz will soon be sinking too; and so, even in shingle or alluvial deposits, gold and quartz are apt to occur as exceedingly close neighbors to each other.
How the gold forms in those old rocks, we have no right to say. Be it remembered, that in newer formations it occurs, although more sparingly. How the gold forms, we do not know. In fact, we have no right to say of gold that it is formed at all. In the present state of chemistry, gold is considered as an element, a simple substance, of which other things are formed, not being itself compounded out of others. In the present state of our knowledge, therefore—and the metals may really be elements—we have nothing to trouble ourselves about. Gold being one of the elements (there are somewhere about forty in all) of which the earth is built, of course existed from the beginning, and will be found in the oldest rocks. It exists, like other elements, in combination. It is combined with iron, antimony, manganese, copper, arsenic, and other things. But it is one great peculiarity of gold that it is not easily oxydized or rusted; rust being caused in metals by the action of oxygen contained in our air. When, therefore, gold, in a compound state, comes to be superficial, the air acting on the mass will generally oxydize the other metals, and so act upon them, more especially where water helps, that in the lapse of time this superficial gold will have been purified in the laboratory of nature, and may be finally picked up in the pure, or nearly pure, state; or else it may be washed, equally pure, from the superficial earth, as is now done in the majority of gold districts. But deep below the surface, in quartz veins contained within the bowels of a mountain—though, to be sure, it is not often found in such positions—gold exists generally in a condition far from pure; the chemistry of the artisan must do what the chemistry of nature had effected in the other case; and this involves rather an expensive process.
Surface gold is found, comparatively pure, in lumps of very various sizes, or in rounded grains, or in small scales. In this state it is found in the Ural district, contained in a mass of coarse gravel, like that found in the neighborhood of London; elsewhere, it is contained in a rough shingle, with much quartz; and elsewhere, in a more mud-like alluvial deposit. The water that has washed it out of its first bed has not been always a mere mountain torrent, or a river, or a succession of rains. Gold shingle and sand have been accumulated in many districts, by the same causes which produced our local drifts, in which the bones of the mammoth, the rhinoceros, and other extinct quadrupeds occur.
The nearly pure gold thus deposited in very superficial layers, may be readily distinguished from all other things that have external resemblance to it. Gold in this state has always, more or less, its well-known color, and the little action of the air upon it causes its particles to glitter, though they be distributed only in minute scales through a bed of sand. But there are other things that glitter. Scales of mica, to the eye only, very much resemble gold. But gold is extremely heavy; twelve or nineteen times heavier than that same bulk of water; mica is very light: sand itself being but three times heavier than water. Let, therefore, sand, with glittering scales in it, be shaken with water, and let us watch the order of the settling. If the scales be gold they will sink first, and quickly, to the bottom; if they be mica, they will take their time, and be among the last to sink. It is this property of gold—its weight—which enables us to obtain it by the process called gold-washing. Earth containing gold, being agitated in water, the gold falls to the bottom. Turbid water containing gold, being poured over a skin, the gold falls and becomes entangled in the hairs; or such water being poured over a board with transverse grooves, the gold is caught in the depressions. This is the reason why the Brazilian searcher looks for a depression in the bottom of the river, and this is also the origin of those peculiar rich bits occasionally found in the alluvium of a large gold-field. Where there has been a hollow, as the water passed it, gold continually was arrested there, forming those valuable deposits which the Brazilians call Caldeiraos. Sometimes, where the waters have been arrested in the hollow of a mountain, they have, in the same way, dropped an excessive store of gold. This quality of weight, therefore, is of prime importance in the history of gold; it determined the character of its deposits in the first instance; it enables us now to extract it easily from its surrounding matter, and enables us to detect it in a piece of rock, where it may not be distinctly visible. There are two substances which look exceedingly like gold;—copper and iron pyrites, substances familiar to most of us. We need never be puzzled to distinguish them. Gold is a soft metal, softer than iron, copper, and silver, although harder than tin or lead. It will scratch tin or lead; but it will be scratched with the other metals. That is to say, you can scratch gold with a common knife. Now, iron pyrites is harder than steel, and therefore a knife will fail to scratch it. Gold and iron pyrites, therefore, need never be mistaken for each other by any man who has a piece of steel about him. Copper pyrites can be scratched with steel. But then there is another very familiar property of gold, by which, in this case, it can be distinguished. Gold is very malleable; beat on it with a stone, and it will flatten, but not break; and when it breaks, it shows that it is torn asunder, by the thready, fibrous nature of its fracture. Beat with a stone on copper pyrites, and it immediately begins to crumble. No acid, by itself, can affect gold; but a mixture of one part nitric, and four parts muriatic acid, is called Aqua Regia, because in this mixture gold does dissolve. A common test for gold, in commerce, is to put nitric acid over it, which has no action if the gold be true. There is, also, a hard smooth stone, called Lydian stone, or flinty jasper, by the mineralogists, and touchstone by the jewelers, on which gold makes a certain mark; and the character of the streak made on such a stone will indicate pretty well the purity or value of the gold that makes it.
We have said that when the gold occurs in a deep-seated vein, combined with other minerals, its extraction becomes no longer a simple process. Let us now point out generally what the nature of this process is, and then we shall conclude our brief discussion; for what else we might say, either lies beyond our present purpose, or has been made, by the talking and writing of the last two years, sufficiently familiar to all listeners or readers. Mr. Gardner, superintendent of the Royal Botanic Garden of Ceylon, thus describes the process of extracting gold out of the mine of Morro Velho. This mine, when St. Hilaire visited it, was considered as exhausted; it is now one of the richest in Brazil. Thus Mr. Gardner writes of it:
"The ore is first removed from its bed by blasting, and it is afterward broken, by female slaves, into small pieces; after which it is conveyed to the stamping-machine, to be reduced to powder. A small stream of water, constantly made to run through them, carries away the pulverized matter to what is called the Strakes—a wooden platform, slightly inclined, and divided into a number of very shallow compartments, of fourteen inches in width, the length being about twenty-six feet. The floor of each of these compartments is covered with pieces of tanned hide, about three feet long, and sixteen inches wide, which have the hair on. The particles of gold are deposited among the hairs, while the earthy matter, being lighter, is washed away. The greater part of the gold dust is collected on the three upper, or head skins, which are changed every four hours, while the lower skins are changed every six or eight hours, according to the richness of the ore. The sand which is washed from the head skins is collected together, and amalgamated with quicksilver, in barrels; while that from the lower skins is conveyed to the washing-house, and concentrated over strakes of similar construction to those of the stamping-mill, till it be rich enough to be amalgamated with that from the head-skins. The barrels into which this rich sand is put, together with the quicksilver, are turned by water; and the process of amalgamation is generally completed in the course of forty-eight hours. When taken out, the amalgam is separated from the sand by washing. It is then pressed on chamois skins, and the quicksilver is separated from the gold by sublimation."
Let us explain those latter processes in more detail. If you dip a gold ring or a sovereign into quicksilver, it will be silvered by it, and the silvering will not come off. This union of theirs is called an amalgam. On a ring or sovereign it is mere silvering; but when the gold is in a state of powder, and the amalgamation takes place on a complete scale, it forms a white, doughy mass, in which there is included much loose quicksilver. This doughy mass is presently washed clear of all impurities, and is then squeezed in skins or cloths, through the pores of which loose quicksilver is forced, and saved for future operations. The rest of the quicksilver is burnt out. Under a moderately strong heat, quicksilver evaporates, or—to speak more scientifically—sublimes; and gold does not. The amalgam, therefore, being subjected to heat, the quicksilver escapes by sublimation, leaving the gold pure. The quicksilver escapes by sublimation; but its owner does not wish it quite to escape out of his premises, because it is an expensive article. Chambers are therefore made over the ovens, in which the mercury may once again condense, and whence it may be collected again afterward. But, with all precaution, a considerable waste always takes place. Other processes are also in use for the separation of gold from its various alloys. We have described that which is of most universal application. Let us not omit noting the significance of the fact, that a quicksilver mine exists in California.