MISCELLANEOUS.
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MISCELLANEOUS.
SODIUM AMALGAM.
The extraction of gold by amalgamation is attended with some difficulties. Whenever sulphides, arsenic, bismuth or tellurium, are present with the gold, they frequently tarnish the metal, and the mercury cannot act upon it. It either "sickens," that is grows thick, or it "flours" that is, divides into small grains, and, in either case, much of the gold escapes in the tailings, and a large part of the mercury itself is carried off in the washing. A mixture of about one per cent, of sodium with the mercury is stated to entirely prevent this. Two claimants dispute the honor of having made this discovery, viz., Mr. Crookes of England, and Dr. Wurtz of New York, who named his amalgam "Magnetic Amalgam."
Dr. Wurtz prepares two kinds of amalgam, No. 1 with two per cent., and No. 2 with four per cent, of sodium. No. 1 is at any time prepared from No. 2, by melting it in an iron pot with its own weight of quicksilver.
Mr. Crookes supplies three kinds of sodium amalgams, known respectively as A, B, and C amalgams. B and C each contain three per cent, of sodium, in addition to which B has a small quantity of zinc in its composition, and C a little tin. A is of seven times the strength of the above, and is prepared in solid bars for shipment.
These various amalgams are used by dissolving one part in from 30 to 100 parts of mercury, and watching its effects during the operation of treating
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the ores. If it retains its fluidity and brightness to the end, it is a sign that a sufficient amount or too much has been added, and a second experiment should be tried with a less quantity of amalgam. But if it be floured, or sickened, or any loss occur, more amalgam may be added until the best proportion is arrived at.
These amalgams adhere strongly to surfaces of iron, steel, platinum, aluminum, and antimony, an adhesion however which is not a true amalgamation, there being no penetration into the substance of the metal, so that the superficially adherent quicksilver may be readily wiped off, just as water may be removed from glass; but as, whenever the ore is ground or agitated with mercury in contact with iron, there is great liability of particles of abraded iron adhering to the amalgam, the following method of manipulation is necessary. The amalgam, after separation from excess of quicksilver, and before retorting, is fused in an earthen dish, or an iron ladle, and the iron which forms a scum on the surface is skimmed off. It is also possible to remove all the iron from the amalgam, by boiling in water, to remove the sodium, without any previous fusion, particularly if the water be made somewhat acid or alkaline.
The use of sodium amalgam was said to have answered well in the Welsh gold mines, and, early in 1866, Mr. Mosheimer went to California to experiment. He gives the following statement of the results. "I worked the same ore side by side with the same machinery, and the results were as follows:--
1st lot, 500 lbs., --with sodium, 85 p. c. of assay; without, 55 p. c.
2nd lot, do. do. 80 p. c. do. do. 60 p. c.
3rd lot, do. do. 78 p. c. do. do. CO p. c."
With reference to this Mr. J. A. Phillips says:-- "At the date of our leaving the mining districts of
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California, in Deer., 1866, although its use had been extensively experimented upon, it had not become generally adopted, and the evidence with regard to its efficiency was considered to be of a conflicting nature. It may, nevertheless, be regarded as certain that no time was lost in practically testing the efficiency of sodium amalgam, and that, had it possessed all the advantages claimed, its use would have long since become general."
SEYMOUR HUGHES' MACHINE.
The stamps are made to revolve, passing over inclined planes, and acting as mullers as well as crushers, rising and dropping as they pass round the battery. The friction usual in stamp mills is thus used to advantage in this machine, for grinding and amalgamating the ore. The machine is arranged for horse, steam, or water power. It is stated that two horses can grind 500 lbs. per hour. The cost per stamp is no more than ordinary batteries, and only ordinary skill is required to set them up. It would, however, seem that the wear of the stamp heads must be very great.
THE STELEFELDT FURNACE
Consists of a chimney about 25 feet or more high, surmounted by screens of various sizes. Flames from furnaces at the base enter the chimney by holes in the sides near the bottom. The ore to be roasted is placed in the screens, which are kept in constant motion, by which means a slight shower of ore is discharged into the flame, the heat of which is sufficient to accomplish the roasting before reaching the bottom. Below the point at which the flames enter is an orifice through which the roasted ore is discharged. It is estimated that a
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single furnace of this description will do all the roasting work required at an ordinary mill, with a battery of twenty stampers.
The ordinary process of roasting takes about six to eight hours to roast l,000 1bs. of ore.
SYSTEM EMPLOYED BY THE PORT PHILIP. COMPANY, (CLUNES'), VICTORIA.
The extent of the claim is 160 acres, on lease for 21 years.
The quartz, when brought to the surface, is separated into two lots. The small size is tipped into a large hopper, and from thence drawn and delivered direct to the stamps, and the larger lumps are sent to the stone-breaking machine, to be reduced to the size suitable to the stamps. The number of stamps at work is eighty, as follows:-- Fifty-six heads, of about six cwt. each, including lifter and tongues, driven by a 24-inch engine, giving seventy-five blows per minute, taking about one horse power per head, and crushing an average of about two tons four cwt. per head in twenty-four hours; twenty-four heads of about eight cwt. each, driven by a 24-inch engine, giving seventy-five blows a minute, and taking in the aggregate about thirty horse power. These stamps crush about four tons each per diem, and they have a larger proportion of the small stuff sent to them. The average quantity of quartz crushed per week of five days, is 1,130 tons. The quantity of water required to work the stamps efficiently, is about eight gallons a head per minute, which is 921,600 gallons per diem. The tailings, on leaving the stamps, run into settling boxes, where the current is checked, and the heavier metals settles. These boxes are cleaned out every few hours, and the material sent
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to the buddle, where it undergoes a further concentration, and is dressed up to an average of three or 4ozs. of gold to the ton of material. This is then sent to the roasting furnace, and afterwards ground in Chilian mills with mercury, and an average of about 85 p. c. of the assay contents is thus extracted. The cost of operating on the pyrites, including the buddle, roasting, grinding, loss of mercury, &c, averages about £2 14s. a ton, or about £1 per oz. of gold obtained. Loss in tailings, 2 dwt. to the ton. In 1865, this Company crushed 54,413 tons of quartz, and obtained from it 20,596ozs. 10 dwts. 12grs. of gold, giving an average of 7dwts. 13grs. per ton. The cost of raising the ore is about 14s. 4 1/2d. a ton, and the cost of treatment 6s. 11d. a ton, making a total cost of £1 1s. 3 1/2d. a ton. The value of the gold was £3 15s. 9d. an ounce, or £1 6s. 8d. per ton of quartz, leaving a profit of 5s. 4d. per ton crushed, which that year must therefore have amounted to about £14,600, from which a royalty of about £6,000 must be deducted, leaving a net profit of about £8,000.
ATTWOOD'S SYSTEM.
Mr. Attwood does not use blankets, but the ground ore issuing from the battery flows at once to the amalgamator, whore it is gently stirred by cylinders armed with knife blades, revolving against the current. It then passes on to a riffle board covered with amalgamated copper plates. The amalgamator has a double bottom, through which a current of steam is passed to heat the mercury. From the riffles the ground material passes into a tye, the bottom of which is inclined at a considerable angle, and which is provided at the lower end with a slot for regulating the depth of water within it. In order to catch any globules of soft
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amalgam or mercury which may become detached from the surfaces of the plates, a small cistern, running the whole breadth of the riffle board, is provided, and a revolving agitator, turning with the current, keeps it free from accumulations to the depth of the arms, so as to form a depression in which the mercury and amalgam may be deposited. The tye is double, and fitted with a moveable tongue which can be placed so as to direct the sand into either of them at pleasure, so that when one tye is filled, the tailings are directed into the other, while the first is being emptied. By this means the pyrites is collected in a very concentrated form, and with very little labour. The concentrated pyrites can afterwards be treated by roasting, and grinding with mercury, or by the chlorination process, or by any of the other means usually employed for extracting the gold from it.
VAN BUREN RYERSON'S GOLD-SAVING PROCESS
Was tried at the Gold Belt mine. The yield of this mine has rarely exceeded eight dollars per ton, but under the new system the average has been over thirty dollars, which is but three per cent, less than the assay. Twenty tons of ore from the Caroline mine was shipped to the new mill at the Gold Belt works, and the yield, which in Carolina had not exceeded four dollars, by the new process exceeded twelve dollars. The difficulty in treating the Virginia ore was the excess of sulphur, which has generally been the enemy of progress in mining regions, and is the source of both trouble and loss in most gold-fields. Ryerson's patent is for the use of super-heated steam, which is steam heated up to a temperature of 1,200 degrees, and to which the crushed ore is exposed fifteen minutes before the quicksilver is added.
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Mr. Ryerson claimed that his process should overcome all previous difficulties, and enable the amalgamator to extract the entire assay, and the result seems to have justified his expectations. He uses a shaking bath 30 feet in length, and with a very peculiar movement; but the one distinctive feature about the process is the super-heated steam. The crusher used at the Gold Belt mine is Brown's Boston machine, which crushes 15 tons a day. It does not work with stamps, but by a centrifugal movement, makes rock crush rock. The cost of the crusher was about 1,000 dollars; the price of Ryerson's machine was 1,500 dollars, with a royalty of 5,000 dollars.
SMELTING GOLD QUARTZ.
From the great infusibility of silica, of which quartz is almost entirely composed, the process of smelting gold ores, that is to say of extracting from them the metal by direct fusion, has hitherto failed in its operation. A Russian gentleman named Anossow, proposed to smelt the auriferous sands of the Ural Mountains with iron ore, instead of subjecting them to the various processes of washing by which they are at present treated. The auriferous cast iron thus obtained was to be dissolved in sulphuric acid, and the gold would remain in the form of an insoluble residue in the bottom of the vessel. This process, although stated by the inventor to be extremely economical, was never practically applied; and, in spite of the assertions to the contrary, its success, if attempted, would be extremely doubtful.
WATERWORKS IN CALIFORNIA IN CONNECTION WITH GOLD MINING.
The demand for a copious supply of water to work the gold deposits at levels far above those of
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the neighbouring rivers, soon called into existence numerous canal and ditch companies, the shareholders being, for the most part, miners. In this way the Middle Yuba Canal Company was formed, the water being brought from a point on the Middle Yuba, a little below Wolsey's Plat, where the river was dammed. The total expenditure, including the various branches, ditches, reservoirs, and extensions, has amounted to about £120,000, and the works are now capable of supplying 38 cubic feet of water per second, or about 1,500 miner's inches; the miner's inch being the quantity of water that will flow through an opening 1 in. square, under a mean head of 6in., or about 9 gallons a minute.
The Eureka Canal is constructed partly of earth, and partly of wooden fluming. The main flume is 6ft. 8in. wide, and 3ft. deep, and it discharges 96 1/2 cubic feet, or 82 gallons of water per second. The two largest aqueducts in California, the Magenta and the National, are on this line of canal. The Magenta aqueduct is 1,400 feet in length, and its greatest height is 126 feet, while the National is 1,800 feet long, with a greatest height of 65 feet. The total length of all the ditches belonging to the Eureka Canal Company, is about 200 miles, and the cost of constructing them was about £200,000. The charge for water is from 10 cents to 40 cents per miner's inch, per working day of ten hours, but the average charge may be estimated at 16 cents, or 8d.
DEEP MINES IN CALIFORNIA.
The North Star vein is worked on its inclination to a depth of 750 feet, and affords quartz yielding, on an average, gold of the value of £7 per ton of 2,000 lbs. In the upper levels the gross value did not exceed £4 a ton.
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The Allison Rranch mine has reached a depth of 600 feet from the surface, and during the first three months of 1866, yielded a net profit of more than £20,000.
The Eureka mine at 400 feet, produces quartz of a value of £9 12s. per ton, quite equal to its average at any former period. Hayward's mine, in Amador County, is worked on its inclination to a depth of 1,250 feet, and yields quartz of much greater value than that obtained from the same vein at shallower levels.
