The Newcastle meeting of the British Association 1889 : report of proceedings reprinted from the "Newcastle Daily Chronicle".
- British Association for the Advancement of Science. Meeting
- Date:
- [1889?]
Licence: Public Domain Mark
Credit: The Newcastle meeting of the British Association 1889 : report of proceedings reprinted from the "Newcastle Daily Chronicle". Source: Wellcome Collection.
178/238 page 174
![The Main Reefveinsareamotifrthelowest or deepest veins, And as the Black Reef and Zur-Bult Reef are the top or uppermost veins of this basin. As the black reef is very tiat, with its north and south outcrop well defined, the main reef in depth will probably follow the same course, :is all were definitely deposited in parallel strata. As work progresses in depth on the main reef, it will be found to flatten, or have a decreasing dip from the horizontal, and then to become horizontal, and perhaps rising to the sur- face, thus forming the southern rim of the basin. As yet no developments nave been made to indicate the vertical distance between the main and black reefs. Many inter- mediate veins have been found between these two ; some of them can be worked profitably. The first work in this district was done on the main reef, and consequently it is more developed than the others. It has been very thoroughly worked and prospected for 30 miles in length, and fairly prospected for 60 miles more. With exceptions of a few faults (forming a very small per- centage of the whole length), the present develop- ment in uniform and continuous pay is over 25 miles long, with every prospect of being found to be much longer. The so-called Main Reef is composed of four parallel veins withm workable distance of each other, aggregating about 15 feet in thickness, the Main Reef being about half of this ; the average yield in gold varying from 8 penny- weights in the Main Reef to 8 ounces in the Robinson leader to the ton. The monthly variation in the average \'ield per ton in the crushings reported by individual mines is caused by varying the proportions of ore from the different veins. A larger amount from the rich leaders will cause a higher average, or a larger amount from the Main Reef will cause a lower average. The variation in the monthly yield is not caused, as many suppose, by change in the yield of the vein : each vein is fairly uniform when compared to itself. The Main Reef veins have been worked for 25 miles in length and to a depth over 200 feet, and, with some few exceptions, have been found uniform in size and jrield. At present there are about 800 stamps crushing ore from the Main Reef mines, crushing about 40,000 tons, and yielding about 30,000 ounces of gold monthly, which gives an average yield of three-quarters of an ounce of gold per ton of ore; this can be taken as the present average yield of the Main Reef, which will probably be largely increased as improved appliances for saving the gold and better management are adopted. Owing to bad mining and milling in many mines (though some are very well managed) the present average expense of mining and milling is probably 30s. per ton. Estimating the gold at its market value of £3 10s. per ounce, this gives :— £ s. d. Average yield of ore per ton 2 12 6 Leas estimated expenses as now worked .... 1 10 0 Net profit per ton at present 1 2 6 This profit will probably be increased to £2 by saving more gold and economies in the working cost, resulting from better arrangement. These figures make the present value of each acre of ground underlaid by the main reef at an angle of 25 degrees, worth over £45,000 net profit, with a strong probability of being soon doubled, as better work is done in mining and milling ; this amount will also increase with the dip of the vein, in consequence of increasing the tonnage per acre. The black reef vein is being worked in many places, and has been traced for a great many miles. It averages 3 feet thick, and yields in the Black Reef mill 16 pennyweights of gold per ton. The total cost of mining and milling this ore is less than 20s. per ton. The Zuur-Bult vein averages 3^ feet thick, and yields 1 ounce of gold per ton, at a total cost of mining and milling of less than 20s. per ton. These two last veins are the top or upper veins of the basin ; as they lie very flat and level, and can be very cheaply worked, they promise to be important gold-producers in the future. The richness of the mines of this district will be seen by comparing them with other mines. For example, take the Alaska Mining and Milling Company's mine, at present the best dividend-paying gold mine in the United States. The following is the working for the six months ending June 15, 1889 :— 108,000 tons crushed, averaj^e yield per ton $3-80 Average cost per ton of luiiiiiig and milling ^1'89 Average net profit per ton $1-91 This shows that ore yielding only about 4 pennyweights of gold to the ton leaves a net profit of one half of the gross yield. The mining laws of the Transvaal will not allow the miner to follow his vein outside of his vertical lines. As the veins are more or less flat, the purchasers or owners of mines should ascertain the extent of vein in the claims from the outcrop or point at which it enters until it leaves the claim by the side lines. This is a very important factor in determining the value of the mines in this district, and has heretofore been overlooked by pur- chasers. As yet nothing has been developed to indicate the depth to which the gold will be found in paying quan- tities. The present developed pay on the Main Reef has been proved by actual work to be at least 30 miles long, with a very uniform yield of gold and ore. It hardly seems possible that it will not bo found to extend down to a great depth. All indications so far developed are that it will. The celebrated Comstock mine of Nevada, United States, might well be called a gold-mine, as the value of the bullion was and is about half gold. The richest body ot ore found there was at 1,500 feet vertical depth ; this deposit paid monthly dividends of £432,000 for several j'ears. There have been a great many profitable deep gold-mines worked in the United States and Australia, many being still in good pay. Mr. C. Algernon Moring, M. Inst. C.E., r.G.S., a very high authority upon mining geology and mining, who has been examining and studying the Transvaal for the past four months, writes as follows about this district:— The whole of this main re !f series has been taken up by different companies, and I have no hesitation in saying that they are the most re- markable and the richest continuous series of gold-mines m the world ; and there is not a single company but should ]3ay large dividends if properly and honestly managed. All the conditions for working are most favourable ; the climate is delightful and healthy throughout the j''ear ; the mines are easily accessible, labour cheap, and there is a plentiful supply of good coal in the immediate vicinity. For several months past about 800stamps have been crushing ore in this district; by the first of the year there will be probably more than double this number. Say 2,000 stamps will be at work, crushing 4,000 tons of ore and producing 3,000 ounces of gold daily, or 75,000 ounces per month. This number will have to be very largely increased in order to crush in any reasonable time the ore already developed in the main reef veins, to say nothing of those required to work the ore from the black reef, Zuur-Bult, Chimes, Botha, and other veins that have been proved already and profitably worked. In 1887 South Africa produced 2 per cent. — the author estimates that this year it will produce 7 per cent., and next year over 15 per cent,—of the total annual product of the gold of the world ; this last amount will be increased proportionately with the increase of addi- tional machinery. This large increase in the annual pro- duction of gold will change the comparative value be- tween gold and silver, unless there will be a corresponding increase in the production of silver. Gold will depreciate and silver appreciate in their comparative values. The author is aware that he is exposing himself to criticism by applying the word basin to a goldtield, and esti- mating the yield of gold by the acre—in fact, he criticised reports made in this manner befere he visited this dis- trict ; but after examining it, and seeing how uniform the yield and thickness of the veins were, and how closely they resembled coal formations, he decided that they should be estimated by the acre the same as coal. The author has examined closely all the principal gold and silver districts of North and South America, but in no case has he seen anything approaching this district in extent and uniformity of yield in ore and metal; veins with almost continuous and uniform pay for 25 miles in length iDeing heretofore unknown in mining. With very few exceptions, all the mines situated on the main reef](https://iiif.wellcomecollection.org/image/b21499317_0178.jp2/full/800%2C/0/default.jpg)
