MINING LECTURE.

Te Aroha News, Volume IV, Issue 183, 18 December 1886, Page 2

MINING LECTURE.

On last evening Mr 11. 11. Ada.ns gave a public lecture in tlio Waiorongomai Public Hall. Subject: My recent trip to the mining districts of Anierica, and what I saw there. There was a largo attendance, and Mr G. Wilson presided, and opened the proceedings by introducing the lecturer with a few remarks suitable for the occasion. Mr Adams, on coming fdrward, Said ; 1 have boen requested by a number of miners and others, rcsideiit in this district to make known by means of a. public lecture what I saw during m j recent trip to the mining districts of America. It is in response to that request that I have asked you here to-night, to impart to you in my own plain and simple way, information that I hope will prove both interesting and useful. I think the most interesting information I can give you will be respecting the manner of treating the various ores in the different places I visited, and to assist me in so doing 1 have prepared a number of diagrams, etc., of different plants I saw atwoik, and havealsosamplesofdifferentoreSjto which I shall refer f:om time to time whilst! speaking to you this evening. The first plant Ipurposcspeakingol u thatkuown aa the Omaha Grand {Smelting Works, situated at Denver. Afc these works ores are purchased for treatment from all the surrounding mining distiicts within a radius of say 800 miles, and they (reat on an average about 2500 tons of ore per week, and provide employment lor about -100 men. These works are very complete, and are in fact looked upon, I believe, as about the best smelting works in the country. They purchase all classes of ores and concentrated pyrites. The success of this concern is in a great measure due to its central position, whereby they are able to obtain ores of every description for treatment. I believe some of the ores I saw there contained fully 75 per cent of lead. Lime and iron stone are also found within a short distance of the works. Part of this plant consists of large calcining funuces, through which all ore sent for treatment is passed which contains a large pur centage of sulphur, prior to its being smelted. The ores are also sampled by means of an elevator, after having been reduced to about the size of an egir. All the ore is made to pass over this elevator, a small per centage fall in"into a box specially consti acted for the purpose, and this is taken as a fair sample of tlie whole for assay purposes. Nine wet jacket smelting furnaces are hero kept at work, very similar to the furnaces introduced into this piovinceby Mr La Monte. Some other smelting works arj also situated at this town, being smaller than that I have been just speaking of, and there is also a small plant, specially for testing ores and showing in addition to their value the method of treatment most suitable, and this is made uso of as a check and guide with regard to the purchase of ore for the furnaces. I will next refer to the .Black Hawk district, where about 700 stampers are kept employed. The stampers used are about 600 pounds each, and are run at a ppeed of from 29 to 33 drops per minute, the drop being twelve inches. The following is the mode of woiking : The stone is fed into the stamper boxes by hand labour, after which it passes over copper tables, veiy similar to what wo use only they are electro-plated, and is ti.en concentrated by means" of Cornish buddies. Quicksilver is used in all the boxes. The only grinder used in theso batteries is a small arastor for the purpose of cleaning the amalgam with. The concentrated pyrites are sold to the smelting companies. The number of stampers in any one battery 'varies froia twelve to eighty, and all theso batteries are very old.- fashioned. .They are distant from Denver about 36 miles. The next plant I visited was ;the Eureka Quartz Reduction Works at 'Nevada. It consists of a" 40 stamp .mill, the stampers weighing' about 600 pounds each, run at an average speed of about 80 blows per minute, with a sixinch drop. At this plant they have 26 combination 1 " pans, and 14 settlers ; the pans are run at a speed of 90 revolutions and the settlers 16 revolutions per minute ; the mode of treatment being as follows : The , ore is first passed through two stone breakers, and from thence through self-feeders', similar to those used at our battery, 1 to the stamper boxes, and from thence it passes into pits, from which 'it is dug out and 'ground in pans, and run into settlers ; afterwards the tailings are conveyed to a large storing dam-, to await some new and cheaper method of further treatment. At those works they claim to savo 70 per cent of both the gold and silver "in the stone ; the loss of mercury per ton of 2000 pounds being two and a half 'pounds, and the cost of treatment one pouud per ton. This plant is working on ore fiom the great Bonanza claim, and the assay valuo of the stone being treated is £5 4s per ton. I will now pass on to the Empire batteiy, Grass

Valley h the property of the Umpire Gold Mining Company. This mill consists of forty stampers running at a speed of 85 blows per minute with a five-inch drop ; the mode of treatment being as follows : First the ore is passed through two stone-breakers, from thence through self-feeders, like we use at Waiorongomai,, to the stamper boxes, and on the copper plates, thence over Frue' concentrators, after which it passes over about 300 feet of blankets outside the mill, it is then allowed io rttn away ; the concentrations being sold by the company sometimes to the smelting companies and sometimes to the proprietors of the chlorination works. In this mill silver is used in the stamper boxes. The only grinding machine ai work in connection with this concern is a small arastor, which is tised for cleaning the amalgam, and this mill is looked upon as one of the best gold-saving mills in the country; the cost of treatment being about 16s per ton of 2000 pounds, and it is claimed that 80 per cent af the assay value of the ore is saved. 1 will next refer to the Providence Gold Mining Battery, containing 40 stamps of about 700 pounds each, run at a speed of eighty-five strokes per minute with a six inch drop ; the mode of treatment adopted being as follows. The stone is fiist passed through two stone breakers, thence through selffeeders similar to those used at the battery at Waiorongomai into the stamper boxes, from whence it passes on to copper plates and Frue concentrators, the t'lilings being allowed to run away. The concentrations are however passed into a large drying room, and from thonce to a circular furnace and roasted, after which they are treated by chlorine process. This company estimate the cost of treatment in the battery at six shillings per ton, and the chlorination process at two pounds ten shillings per ton. Only such gold ores as are found to concentrate satisfactorily are ticatcd by this method. The Idaho Gold Mining Company's forty stamper battery was the one I next visited, the stampers are run at a speed of sixty strokes per minute, with a seven inch drop. At this battery the ore is first of all passed through one stone breaker, and then into the stamper boxes, over blankets on to shaking tables, and from thence into Cornish buddies, after which it is run over three hundred feet of blankets on the outside ot the battery, it is then sold to the proprietors of small tailing plants further down the creek. The ore treated at this battery is valued at six pounds per ton. I will now refer to the Selby smelting works at San Francisco, where about six hundred tons of ore per week are treated ; and in connection with which are large refining and calcining furnaces. At these works gold, silver, and lead are produced in a pure state. The furnaces used are wet jacket furnaces, and the ores for treatment are purchased from all parts of California. The success this plant has proved is no doubt in a great measure attributable to its position, as ore can be brought from all quarters. From « hat I saw during my visit to California and from what I have seen of our own districts I think the oics of Waihi, lvarangahake, Tui and Waiorongomai can bo successfully treated as follows. First crubh, and save all free milling gold by the ordinary battery process ; save all tailings and roast them in a calcining furnace, after which they should be ground in cither pans or berdans. Were the method of treatment, I have just mentioned, adopted I feel certain fully eighty-five per cent of all the geld and silver in the stone would be saved. The loss sustained by the mode of treatment at present generally used amongst us is in the form of tellurium ; and in order to make tellurium amalgamate firo must be used ; at least that is the opinion I have come to. The total cost; of treating ore by the method I havo jusc advocated need not exceed twenty shillings per ton. I believe sulphide of silver exists in payable quantities from here to OO f \pe Colville. With respect to our berdans, I may say that I met with no one who appeared to know anything about them, and when I showed drawings of them some- were greatly taken with them, and in fact 1 had to promise to write and forward working drawings of thorn. lam here to-night to give any other information any of those present jmay ask me, and to explain all about the ores, I cannot conclude without referring to the very great courtesy extended to me by our American cousins, in fact I shall never forget the kindness I received. At every mining camp I found those in charge most willing to explain everything to me. I would strongly recommend upon the miners of this peninsula to uige upon Government the necessity of constructing a small combination plant at which ores from the various reefs could be tested, and the best method of treating ores proved. Such a plant should include the following machinery : , One small wet jacket galena smelter, one small stonebreaker, two stampers, one calcining furnace, and one small chlorination plant. Such a combination plant as the above would enable the best method of treatment for ores from the various districts to be proved ; and you well know the method, suitable for one district in all probability will not suit another! I feel sure if Government would erect such a plant as> Thavo described, it would be the means of discovering'payable reefs.' It is my opinion this district contains .Vast quantities'of both -gold and silver in the' form of tellurium. Ido not believe that we now save more than 70 per cent of all the gold and silver, and the public do not suppose we save so much, but I think we do. lam of opinion that this district is not at present adapted-for smelt-

ing, through lack of greater railway facilities, by means of which the various ores for fluxing could be brought to one centre at a low rate. All purchases in America are made on the basis of 90 per cent of the assay value, or if very damp about 80 per cent. The lecture was most interesting throughout and listened to" with great |, attention,; and during its delivery Mr Adams simplified matters by frequently referring to a number of plans and" diagrams of the vnrioils plants he had visited, and samples of ores, tailings, gratings, etc., and kindly volunteered to givo any further information asked for. On the motion of Mr Munro, a hearty vote of thanks was passed to Mr J. 0. Firth for sending for Mr Adams to go and visit all these mining districts ; and Mv Munro was authorised to convene a public meeting for the second Saturday in January, to take steps with respect to Mr Adams' suggestion re the erection of a combination plant by Government. Hearty votes of thanks were passed Mr Adams for his lecture, to Mr Wilson for presiding, etc.