The Romance of Industry and Invention Part 5

[Ill.u.s.tration]

CHAPTER V.

GOLD AND DIAMONDS.

GOLD.--How widely distributed--Alluvial Gold-mining--Vein Gold-mining--Nuggets--Treatment of Ore and Gold in the Transvaal--Story of South African Gold-fields--Gold-production of the World--Johannesburg the Golden City--Coolgardie Gold-fields--Bayley's discovery of Gold there.

DIAMONDS.--Composition--Diamond-cutting--Diamond-mining--Famous Diamonds--Cecil J. Rhodes and the Kimberley Mines.

In the getting of gold--the metal--for the purpose of possessing gold--as money--there has always been an element of excitement and romance.

'How quickly nature falls into revolt when gold becomes her object!' as Shakespeare says:

For gold the merchant ploughs the main, The farmer ploughs the manor.

There is a vast difference between the way in which the precious metal is now extracted and the primitive methods which were considered perfect in the earlier part of the century. The miner of fifty years ago never dreamt of machinery, costly and magnificent, capable of crushing thousands of tons of quartz per week. He 'dollied,' or ground, his little bits of rock by means of a contrivance resembling a pestle and mortar, and it was only the very richest stone that repaid him for his labour. In fact, there was very little crushing in those days, quartz not being easily found sufficiently rich to make such work a paying concern, and it was therefore alluvial gold which was chiefly sought for. The gold-seeker having decided on the place where he was to make his first venture, provided himself with a shovel and pick and started for the 'diggings.' Gold-mining was then carried on all over California, and he had his choice of many camps.

[Ill.u.s.tration: The Hand-cradle Method of extracting Gold.]

But what a wild and lawless place was California in those days! Here in these gold-fields were gathered together thousands of the greatest desperadoes that the earth could boast of, and thousands of needy, if harmless, adventurers from every country in the world. Fortunately with them were mixed thousands of honest hard-working men, of every condition in life, from the peer to the peasant, men who had been doing well, or fairly well, at their professions, or in their business offices at home, but for whom the attractions of this El Dorado had proved too powerful.

Gold is perhaps the most widely and universally sought product of the earth's crust. In the very earliest writings which have come down to us gold is mentioned as an object of men's search, and as a commodity of extreme value for purposes of adornment and as a medium of exchange. The importance which it possessed in ancient times has certainly not lessened in our day. Without the enormous supplies of gold produced at about the time when the steam-engine was being brought into practical use it is difficult to imagine how our commerce could have attained its present proportions; and but for the rush of immigrants to the gold-fields in the beginning of the second half of this century Australia might have remained a mere convict settlement, California have become but a granary and vineyard, and the Transvaal an asylum of the Boers who were discontented with the Cape government.

On the score of geographical distribution, gold must be deemed a common metal, as common as copper, lead, or silver, and far more common than nickel, cobalt, platinum, and many others. Theorists have propounded curious rules for the occurrence of gold on certain lines and belts, which have no existence but in their own fancy. Scarcely a country but has rewarded a systematic search for gold, though some are more richly endowed than others, and discoveries are not always made with the same facility. The old prejudices, which made men a.s.sociate gold only with certain localities hindered the development of a most promising industry even within the British sh.o.r.es. Despite the abundant traces of ancient Roman and other workings, the gold-mines of Wales were long regarded as mythical; but recent extended exploitation has proved them to be rich. This is notably the case in the Dolgelly district, where considerable gold occurs, both in alluvial gravels and in well-formed quartz veins traversing the Lower Silurian Lingula beds and the intruded diabasic rocks called 'greenstone' in the Geological Survey. A peculiarity of the veins is the common a.s.sociation of magnesian minerals. The gold is about 20 or 21 carats fine, and often shows traces of iron sesquioxide. So long ago as 1861 some 10,000 worth of gold per annum was taken out of the Clogan mine by imperfect methods. Some samples have afforded 40 to 60 ounces per ton--a most remarkable yield.

There are probably many veins still waiting discovery.

A calculation was made in 1881 that the total gold extracted from all sources up to that date from the creation had been over 10,000 tons, with a value of about 1500 millions sterling. California, to the end of 1888, was reckoned to have afforded over 200 million pounds' worth, and this figure is exceeded by the Australian colony of Victoria.

The origin of gold-bearing mineral veins is inseparably connected with that vexed question, the origin of mineral veins generally. By far the most common matrix of vein-gold is quartz or silica, but it is not the only one. To pa.s.s by the metals and metallic ores with which gold is found, there are several other minerals which serve as an envelope for the precious metal. Chief among them is lime. Some of the best mines of New South Wales are in calcareous veins. Sundry gold-reefs in Queensland, New South Wales, Victoria, and Bohemia are full of calcite.

Dolomite occurs in Californian and Manitoban mines; and apat.i.te, aragonite, gypsum, selenite, and crystalline limestone have all proved auriferous, while in some cases neighbouring quartz has been barren.

Felspar in Colorado and felsite magnesian slate in Newfoundland carry gold.

NUGGETS.

[Ill.u.s.tration: Welcome Nugget.]

The physical conditions under which gold occurs are extremely variable.

Popularly speaking, the most familiar form is the 'nugget,' or shapeless ma.s.s of appreciable size. These, however, const.i.tute in the aggregate but a small proportion of the gold yielded by any field, and were much more common in the early days of placer-mining in California and Australia than they are now. One of the largest ever found, the 'Welcome' nugget, discovered in 1858 at Bakery Hill, Ballarat, weighed 2217 ounces 16 dwt., and sold for 10,500, whilst not a few have exceeded 1000 ounces. One found at Ca.s.son Hill, Calaveras county, California, in 1854, weighed 180 pounds. The 'Water Moon' nugget, found in Australia in 1852, weighed 223 pounds. The origin of these large nuggets has been a subject for discussion. Like all placer or alluvial gold, they have been in part at least derived from the auriferous veins traversing the rocks whose disintegration furnished the material forming the gravel beds in which the nuggets are found.

The famous nugget known as the 'Welcome Stranger' was discovered under singular circ.u.mstances in the Dunolly district of Victoria, which is one hundred and ten miles north-west of the capital, Melbourne, by two Cornish miners named Deeson and Oates. Their career is remarkable, as showing how fortune, after frowning for years, will suddenly smile on the objects of her apparent aversion. These two Cornishmen emigrated from England to Australia by the same vessel in 1854. They betook themselves to the far-famed Sandhurst Gold-field in Victoria; they worked together industriously for years, and yet only contrived to make a bare livelihood by their exertions. Thinking that change of place might possibly mean change of luck, they moved to the Dunolly Gold-field, and their spirits were considerably raised by the discovery of some small nuggets. But this was only a momentary gleam of sunshine, for their former ill-luck pursued them again, and pursued them even more relentlessly than before.

The time at last came, on the morning of Friday, February 5, 1869, when the storekeeper with whom they were accustomed to deal refused to supply them any longer with the necessaries of life until they liquidated the debt they had already incurred. For the first time in their lives they went hungry to work, and the spectacle of these two brave fellows fighting on an empty stomach against continued ill-luck must have moved the fickle G.o.ddess to pity and repentance. Gloomy and depressed as they naturally were, they plied their picks with indomitable perseverance, and while Deeson was breaking up the earth around the roots of a tree, his pick suddenly and sharply rebounded by reason of its having struck some very hard substance. 'Come and see what this is,' he called out to his mate. To their astonishment, 'this' turned out to be the 'Welcome Stranger' nugget; and thus two poverty-stricken Cornish miners became in a moment the possessors of the largest ma.s.s of gold that mortal eyes ever saw, or are likely to see again. Such a revolution of fortune is probably unique in the annals of the human race. Almost bewildered by the unexpected treasure they had found at their feet, Deeson and Oates removed the superinc.u.mbent clay, and there revealed to their wondering eyes was a lump of gold, a foot long and a foot broad, and so heavy that their joint strength could scarcely move it. A dray having been procured, the monster nugget was escorted by an admiring procession into the town of Dunolly, and carried into the local branch of the London Chartered Bank, where it was weighed, and found to contain 2268-1/2 ounces of gold. The Bank purchased the nugget for 9534, which the erstwhile so unlucky, but now so fortunate, pair of Cornish miners divided equally between them. Whether the storekeeper who refused them the materials for a breakfast that morning apologised for his harsh behaviour, history relates not, but the probability is that he was paid the precise amount of his debt and no more; whereas, had he acted in a more generous spirit towards two brothers in distress, he might have come in for a handsome present out of the proceeds of the 'Welcome Stranger.'

The 'Welcome' nugget above mentioned, found at Bakery Hill, Ballarat, in Victoria, on June 15, 1858, was nearly as large as the one just described, its weight being 2217 ounces 16 dwts. It was found at a depth of one hundred and eighty feet in a claim belonging to a party of twenty-four men, who disposed of it for 10,500. A smaller nugget, weighing 571 ounces, was found in close proximity to it. After being exhibited in Melbourne, the 'Welcome' nugget was brought to London and smelted in November 1859. The a.s.say showed that it contained 99.20 per cent. of gold.

Another valuable nugget, which was brought to London and exhibited at the Crystal Palace, Sydenham, was the 'Blanche Barkly,' found by a party of four diggers on August 27, 1857, at Kingower, Victoria, just thirteen feet beneath the surface. It was twenty-eight inches long, ten inches broad in its widest part, and weighed 1743 ounces 13 dwts. It realised 6905, 12s. 6d. A peculiarity about this nugget was the manner in which it had eluded the efforts of previous parties to capture it. Three years before its discovery, a number of miners, judging the place to be a 'likely' locality, had sunk holes within a few feet of the spot where this golden ma.s.s was reposing, and yet they were not lucky enough to strike it. What a tantalising thought it must have been in after-years, when they reflected on the fact that they were once within an arm's length of 7000 without being fortunate enough to grasp the golden treasure! Kingower, like Dunolly, from which it is only a few miles distant, is a locality famous for its nuggets. One weighing 230 ounces was actually found on the surface covered with green moss; and pieces of gold have frequently been picked up there after heavy rains, the water washing away the thin coating of earth that had previously concealed them. Two men working in the Kingower district in 1860 found a very fine nugget, weighing 805 ounces, within a foot of the surface; and one of 715 ounces was unearthed at Daisy Hill at a depth of only three and a half feet.

A notable instance of rapid fortune was that of a party of four, who, having been but a few months in the colony of Victoria, were lucky enough to alight on a nugget weighing 1615 ounces. They immediately returned to England with their prize and sold it for 5532, 7s. 4d. The place where they thus quickly made their 'pile,' to use an expressive colonialism, was Canadian Gully, at Ballarat, a very prolific nugget-ground. There was also found the 'Lady Hotham' nugget, called after the wife of Sir Charles Hotham, one of the early governors of Victoria. It was discovered on September 8, 1854, at a depth of 135 feet. Its weight was 1177 ounces; and near it were found a number of smaller nuggets of the aggregate weight of 2600 ounces, so that the total value of the gold extracted from this one claim was no less than 13,000. As showing the phenomenal richness of this locality, it may be added that on January 20, 1853, a party of three brought to the surface a solid ma.s.s of gold weighing 1117 ounces; and two days afterwards, in the same tunnel, a splendid pyramidal-shaped nugget weighing 1011 ounces was discovered; the conjoint value of the two being 7500.

A case somewhat similar to one already described was that of the 'Heron'

nugget, a solid ma.s.s of gold to the amount of 1008 ounces, which was found at Fryer's Creek, Victoria, by two young men who had only been three months in the colony. They were offered 4000 for it in Victoria; but they preferred to bring it to England as a trophy, and there they sold it for 4080.

The 'Victoria' nugget, as its name suggests, was purchased by the Victorian government for presentation to Her Majesty. It was a very pretty specimen of 340 ounces, worth 1650, and was discovered at White Horse Gully, Sandhurst. Quite close to it, and within a foot of the surface, was found the 'Das...o...b..' nugget, weighing 330 ounces, which was also brought to London, and sold for 1500.

Just as a book should never be judged by its cover, so mineral substances should not be estimated by superficial indications. A neglect of this salutary precept was once very nearly resulting in the loss of a valuable Victorian nugget. A big lump of quartz was brought to the surface, and, as its exterior aspect presented only slight indications of the existence of gold, it was at first believed to be valueless; but as soon as the ma.s.s was broken up, there, embedded in the quartz, was a beautiful nugget of an oval shape.

New South Wales, the parent colony of the Australian group, has produced a considerable quant.i.ty of gold, but not many notable nuggets. Its most famous nugget was discovered by a native boy in June 1851 at Meroo Creek, near the present town of Bathurst. This black boy was in the employ of Dr Kerr as a shepherd, and one day, whilst minding his sheep, he casually came across three detached pieces of quartz. He tried to turn over the largest of the pieces with his stick; but he was astonished to find that the lump was much heavier than the ordinary quartz with which he was familiar. Bending down and looking closer, he saw a shining yellow ma.s.s lying near; and when he at last succeeded in lifting up the piece of quartz, his eyes expanded on observing that the whole of its under surface was of the same shining complexion. He probably did not realise the full value of his discovery; but he had sufficient sense to break off a few specimens and hasten to show them to his master. Dr Kerr set off at once to verify the discovery; and when he arrived at the spot, his most sanguine antic.i.p.ations were fulfilled by the event. He found himself the possessor of 1272 ounces of gold; and he rewarded the author of his wealth, the little black boy, with a flock of sheep and as much land as was needed for their pasture.

METHODS OF MINING.

The more common form of alluvial gold is as grains, or scales, or dust, varying in size from that of ordinary gunpowder to a minuteness that is invisible to the naked eye. Sometimes indeed the particles are so small that they are known as 'paint' gold, forming a scarcely perceptible coating on fragments of rock. When the gold is very fine or in very thin scales, much of it is lost in the ordinary processes for treating gravels, by reason of the fact that it will actually float on water for a considerable distance.

From what has been already said it will be evident that gold-mining must be an industry presenting several distinct phases. These may be cla.s.sed as alluvial mining, vein-mining, and the treatment of auriferous ores.

In alluvial mining natural agencies, such as frost, rain, &c., have, in the course of centuries, performed the arduous tasks of breaking up the matrix which held the gold, and washing away much of the valueless material, leaving the gold concentrated into a limited area by virtue of its great specific gravity. Hence it is never safe to a.s.sume that the portion of the veins remaining as such will yield anything like so great an equivalent of gold as the alluvials formed from the portion which has been disintegrated. As water has been the chief (but not the only) agent in distributing the gold and gravel const.i.tuting alluvial diggings or placers, the banks and beds of running streams in the neighbourhood of auriferous veins are likely spots for the prospector, who finds in the flowing water of the stream the means of separating the heavy grains of gold from the much lighter particles of rock, sand, and mud. Often the brook is made to yield the gold it transports by the simple expedient of placing in it obstacles which will arrest the gold without obstructing the lighter matters. Jason's golden fleece was probably a sheepskin which had been pegged down in the current of the Phasis till a quant.i.ty of gold grains had become entangled among the wool. To this day the same practice is followed with ox-hides in Brazil, and with sheepskins in Ladakh, Savoy, and Hungary. This may be deemed the simplest form of 'alluvial mining.' If the gold deposited in holes and behind bars in the bed of the stream is to be recovered, greater preparations are needed.

Either the river-bed must be dredged by floating dredgers, worked by the stream or otherwise; or the gravel must be dug out for washing while the bed is left dry in hot weather; or the river must be diverted into another channel (natural or artificial) whilst its bed is being stripped. The first-named method is best adapted to large volumes of water, but probably is least productive of gold, pa.s.sing over much that is buried in crevices in the solid bed-rock. The second plan is applicable only to small streams, and entails much labour. The third is most efficient, but very liable to serious interference by floods, which entail a heavy loss of plant.

In searching for placers it is necessary to bear in mind that the watercourses of the country have not always flowed in the channels they now occupy. During the long periods of geological time many and vast changes have taken place in the contour of the earth's surface. Hence it is not an uncommon circ.u.mstance to find beds of auriferous gravel occupying the summits of hills, which must, at the time the deposit was made, have represented the course of a stream. In the same way the remains of riverine acc.u.mulations are found forming 'terraces' or 'benches' on the flanks of hills. Lacustrine beds may similarly occur at alt.i.tudes far above the reach of any existing stream, having been the work of rivers long since pa.s.sed away.

Another form of alluvial digging occurs in Western America and New Zealand, where the sea washes up auriferous sands. These are known as 'ocean placers' or 'beach diggings,' and are of minor importance.

Whilst most placers have been formed by flowing water, some owe their origin to the action of ice, and are really glacial moraines. Others are attributed to the effects of repeated frost and thaw in decomposing the rocks and causing rearrangement of the component parts. Yet another cla.s.s of deposits is supposed to have been acc.u.mulated by an outpouring of volcanic mud. And, finally, experts declare that some of the rich _banket_ beds of the Transvaal became auriferous by the infiltration of water containing a minute proportion of gold in solution.

In all cases the recovery of alluvial gold is in principle remarkably simple. It depends on the fact that the gold is about seven times as heavy, bulk for bulk, as the material forming the ma.s.s of the deposit.

The medium for effecting the separation is water in motion. The apparatus in which it is applied may be a 'pan,' a 'cradle,' or a 'tom,'

for operations on a very small scale, or a 'sluice,' which may be a paved ditch or a wooden 'flume' of great length, for large operations.

The method is the same in all: flowing water removes the earthy matters, while obstructions of various kinds arrest the metal. As a rule, it is more advantageous to conduct the water to the material than to carry the material to water. In many cases a stream of water, conveyed by means of pipes, and acting under the influence of considerable pressure, is utilised for removing as well as washing the deposit. This method is known as 'piping' or 'hydraulicing' in America, where it has been chiefly developed, but is now forbidden in many localities, because the enormous ma.s.ses of earth washed through the sluices have silted up rivers and harbours, and caused immense loss to the agricultural interest by burying the rich riverside lands under a deposit that will be sterile for many years to come. The plan permits of very economical working in large quant.i.ties, but is extremely wasteful of gold. The water-supply is of paramount importance, and has led to the construction of reservoirs and conduits, at very heavy cost, which in many places will have a permanent value long after gold-sluicing has ceased. These large water-supply works are often in the hands of distinct parties from the miners, the latter purchasing the water they use. To give an example of the results attained in alluvial mining, it may be mentioned that in a three-months' working in one Victorian district in 1888, over 33,500 tons of wash-dirt were treated for an average yield of 18-1/2 grains of gold per ton, or, say, one part in 700,000. Where water cannot be obtained recourse is had to a fanning or winnowing process for separating the gold from the sand, which, however, is less efficacious.

[Ill.u.s.tration: Hydraulic Gold-mining.]

Vein-mining for gold differs but little from working any other kind of metalliferous lode. When the vein-stuff has been raised it is reduced to a pulverulent condition, to liberate the gold from the gangue. In some cases roasting is first resorted to. This causes friability, and facilitates the subsequent comminution. When the gold is in a very fine state, too, it helps it to agglomerate. But if any pyrites are present the effect is most detrimental, the gold becoming coated with a film of sulphur or a glazing of iron oxide. The powdering of the vein-stuff is usually performed in stamp batteries, which consist of a number of falling hammers. While simple in principle, the apparatus is complicated in its working parts, and is probably destined to give way to the improved forms of crushing-rolls and centrifugal roller mills, which are less costly, simpler, more efficient, and do not flatten the gold particles so much. One of the most effective is that by Jordan. When the vein-stuff has been reduced to powder, it is akin to alluvial wash-dirt, and demands the same or similar contrivances for arresting the liberated gold and releasing the tailings--that is, mercury troughs, amalgamated plates, blanket strakes, &c.; but, in addition, provision is made for catching the other metalliferous const.i.tuents, such as pyrites, which almost always carry a valuable percentage of gold. These pyrites or 'sulphurets' are cleansed by concentration in various kinds of apparatus, all depending on the greater specific gravity of the portion sought to be saved.

Of the metals and minerals with which gold is found intimately a.s.sociated in nature are the following: Antimony, a.r.s.enic, bis.m.u.th, cobalt, copper, iridium, iron, lead, manganese, nickel, osmium, palladium, platinum, selenium, silver, tellurium, tungsten, vanadium, and zinc, often as an alloy in the case of palladium, platinum, selenium, silver (always), and tellurium. The methods of separation vary with the nature of the ore and the conditions of the locality.

TREATMENT OF ORE AND GOLD IN THE TRANSVAAL.

The method of treatment of ore and gold in the Transvaal, the most perfect and effective known at the present time, has thus been described by Arthur Stenhouse:

The rock when hoisted out of the mine is first a.s.sorted, the waste rock being thrown on one side and the gold-bearing ore broken into lumps by a stone-breaker. The lumps of ore now pa.s.s by gravitation and feeders through a battery (or stamp mill), each stamp of which weighs about 1150 pounds, every stamp being lifted and dropped separately by the cam shaft at a speed of about 95 drops a minute. A stream of water is introduced, the ore is crushed into fine sand, and is carried by the water over a series of inclined copper plates, which are coated with quicksilver. The free gold in the sand at once amalgamates with the quicksilver on the plates, and the sand-laden stream continues on its course.

The sand, having now pa.s.sed over the plates, is carried by launders on to the concentrators, or frue vanners. These concentrators separate and retain the heavy sand (or concentrates), whilst the lighter sand is carried by gravitation through a trough (or launder) to the cyanide vats.