VISIT TO THE STONECROFT AND GREYSIDE LEAD MINES, THE PRUDHAM QUARRIES, AND THE SETTLING STONES LEAD MINES, OCTOBER 13TH, 1877.
AT the time of starting from Newcastle it was found that upwards of a hundred members had availed themselves of the kind permission of the Stonecroft and Greyside Mining Company, Mr. T. W. Benson, and Mr. F. W. Hall, to view the quarries and lead mines near Newbrough; and at 1015 the special train, kindly placed at the disposal of the Institute, took the party to its destination.
At Fourstones the party was received by Mr. Benson and his son, Mr. T. IV. Benson, and conducted over the colliery, limeworks, and quarries belonging to the former gentleman. The first thing to attract the attention of the visitors was Hunter's patent stone-dressing machine, employed in dressing the stones obtained from the quarry. It was put in operation on the arrival of the visitors, and a stone about five feet nine inches in length and eighteen inches broad was dressed in about four and a half minutes. This, however, was no test of the quantity of work the machine is capable of doing in the time, for it will dress a stone twice the breadth in the same time, and in practice it does the work of from fifteen to thirty men according to the breadth of stone. The machine is a great improvement upon those of the same kind formerly used. In the older machines the cut was straight upon the face of the stone, and consequently the wear and tear of the knives was very great. In the new arrangement, the cutters revolve upon an axle, so that the cut is given in the shape of a curve or scoop, and consequently the edge of the cutter is much less damaged than in the former case. The machine is capable of dressing 300 superficial feet per day. In the same works are machines for similarly saving manual labour in the case of timber sawing and planing: The instruments are both manufactured by Messrs. Ransome and Co., of Chelsea, London. One is a band saw which cuts out curves, cart-wheel felloes, brake wheels, and similar articles, and does the work of seven or eight men; the other is a boring, sawing, and planing machine. It is used for morticing door frames as well as cutting, and does an immense quantity of work. An instrument, by the same makers, also in this workshop, is used for sharpening saws. It consists of a circular disc of emery stone, about ten and a half inches in diameter, attached to a swing frame, revolving at a very high speed. This frame can, by means of a handle, be raised or lowered at the will of the operator; the saw is fixed below, and the disc is brought down on the teeth. The emery stone cuts the steel with the greatest rapidity, and the saw is speedily sharpened.
The party next visited the selenitic works at the same place. They comprise a pair of edge stones and four .feet six inches mill stones, elevators, etc. The material produced is largely used for plastering in place of mortar.
Here also are nine lime-kilns capable of turning out 150 tons of lime per day, and adjoining is a colliery employing between fifty and sixty men and boys. The coal is found in the limestone measures, and from the circumstance of its lying immediately underneath them is not unfrequently called the Little Limestone coal. The quarries of limestone and freestone are situated about half a mile to the north of the railway station. The freestone is the well-known Prudham stone, so largely used for building purposes, and the only stone of the kind to be found in the district. At this place and in the immediate neighbourhood alone, is found the stratum of this quality. Large quantities are sent into Lancashire, Westmorland, and Scotland for the construction of buildings of the better class. Some of the principal buildings in Newcastle, the new Post Office, the Mining Institute, the new Club House, and the Central Station, are built of it. The limestone which Mr. Benson is working is lying immediately over this, and is the well-known Great Limestone prevailing over the whole of the mining district of the North of England, and which in the Alston Moor and adjacent lead mining territories has been and is still so productive of lead ore. In the district of Newbrough, Fourstones, and Prudham it is denuded; and the lead ore is raised from beds immediately underneath, down to the whir sill, and also upon the whip sill.
To enable the members more particularly to observe the leading features of the Stonecroft and Settlingstones lead-mines, the following description of the geological features of the neighbourhood to be visited was kindly supplied by G. A. Leboar, Esq., F.G.S.
The group of lead-mines between Haydon Bridge and the line of the Roman Wall is situated (geologically speaking) in the tipper portion of the Bernician or Carboniferous Limestone Series of Northumberland, the beds exposed lying between the "Little Limestone" above and the strata associated with the Great Whin Sill below.
A walk from Fourstones Station, northwards, to the Roman Wall, on Limestone Edge, exhibits the successive outcrops of the rocks in question admirably.
The Little Limestone coal (the same as that worked at Acomb) crops out at the railway station; the dip of the beds being S. to S.E., and at a considerably greater angle than the slope of the country, every step towards Teppermoor takes one from higher to lower beds. In this way is passed over the " Great Limestone" in which are opened the large quarries at Fourstones ; the Prudham Sandstone, also largely quarried; the " Fourfathom Limestone," which is well seen in a small quarry in a corner of the Newbrough grounds, just below the great quarries, and which here abounds in the curious fossil, Scireammina Carteri, Brady; then come other conspicuous sandstones and grits with limestones, until one of the latter is found lying immediately upon the great sheet of basalt, which is so well known as the Great Whin Sill. The horizon occupied by the Whin here is about 400 feet higher than that at which it stands at its next prominent outburst (well seen in the distance to the N.E. from Limestone Edge) at Gunnerton Heugh. In places, the Limestone capping the Whin is seen to be separated from it by a thin bed of shale; and when this is the case, the shale is seen very clearly to be burnt and baked by its proximity to the igneous rock. This, together with its change of horizons, even if unsupported by other facts, would be amply sufficient proof of the intrusive character of the Great Whin Sill. In the mines themselves, where the sheet of trap is faulted by the veins in the same manner as the sedimentary sandstones and limestones,- the deceptive interbedded appearance of the Whin is that which is best shown.
Roughly speaking, the veins of the district as a whole may be said to run in a broad band, having a N.E. and S.W. direction, and lying between the Prudham and Carr Edge Hills on the East, and the Grindon Hills on the West. The individual directions and throws of the veins are of course various, and it is only of their complicated network collectively that the above general statement is true. Of the veins little need here be said, but attention may perhaps be called to the following points, wherein they differ from those of the Alston and Derwent districts, viz., their throws as faults are frequently great, although taken together they in the end compensate one another ; their hades are sometimes to the upthrow (or, in other words, they are sometimes reversed faults), and they frequently are very rich in Carbonate and (less markedly) in Sulphate of Barytes. The spar filling tip vein-cavities is generally Carbonate of Lime, and very rarely Fluor-spar.
The Great Fallowfield Vein, which may fire regarded as the advanced guard of the whole group, although it lies outside the limits mentioned, crosses the South Tyne in a line nearly, but not quite, parallel to that of the St. Oswald's Basaltic Dyke, a little below the Fourstoues Station.
A great portion of the lead-mining area, as above circumscribed, lies in a comparative hollow, which is more or less filled up with Boulder Clay. The re-assortment of this clay has given rise to detached patches of finer clay suitable for tile-making, etc., and which have been utilized in this manner at Fourstones, etc.
A still newer deposit is that of ancient river gravels, which are beautifully seen on both sides of the South Tyne valley, rising in well shaped terraces to a height of 300 feet and more. To the fossil hunter, the thick shale above the Great Limestone in the Fourstones quarries, and the Four-fathoms Limestone in the small but rich Newbrough quarry, are the chief attractions, whilst the mineralogist will find much to interest him in the beautiful specimens of Witherite to be seen in the neighbourhood of the. mines.
The Stonecroft Mines, the property of the Stonecroft and Greyside Mining Company, are about two miles and a quarter from the Fourstones Station. The members who went underground were conducted through the workings by the chief agent, Mr. Thomas Ware, and the surface operations were shown by Mr. Benson, one of the managing partners.
The mines have been worked on three distinct veins, the first Main Vein, runs nearly due E. and W., and has an upthrow to the north of 14 fathoms. It has been worked extensively, and proved more or less productive the whole length, varying very much at times from very rich to poor. The second, known as the South X Vein, has been extensively worked, but not so productive. Its throw is comparatively small. The third, the South Vein, has also been worked to a considerable extent, and has been very productive. This vein has an upthrow to the north of 14 fathoms. The matrix is composed of Carbonate of Iron, Sulphate and Carbonate of Barytes, and Iron Pyrites.
About 130 men are employed in the underground workings, and about 70 at the surface.
The great art of lead mining is in driving amongst and towards those portions of the veins which contain the most lead. In some cases the choice of direction, to some extent, is allowed the men, who are paid on the lead actually procured at stated settling times, drawing money from time to time in the interim for their daily wants. This, of course, causes them to make as little dead work as possible. In other cases the men are paid by the square fathom, i.e., 6 feet high and 6 feet forward, and such width as may be indicated to them by the superintendent.
In these mines the latter system prevails. All that portion of the matrix that can at sight be seen to contain no lead is left below, and that sent to bank contains on an average 12 to 15 per cent. of lead; and it is to separate this from the matrix, by means of crushing, washing, and the action of gravity, that the surface works are constructed. The first process consists of screening the material close to the opening from the mine. Here the stones are wailed, the pure lead ore selected and set apart, and that portion of the matrix containing lead allowed to descend into a crushing machine, where it is reduced to pieces from the size of nuts to that of the finest sand.
. It has been found that in washing, the lead can be very much more easily separated from the matrix if the particles of a similar size are treated together and not mixed with each other. The first thing, therefore, is to size the particles coming from the crushing machine. They are accordingly lifted by a series of buckets from the well where they are deposited by the machine and conducted, mixed' with a stream of water, to the top of a series of circular rotating sieves, placed at an angle ; the largest meshes of this sieve are at the top, and the largest particles fall through it first, leaving the smallest, which are carried by the rush of water, to escape at the bottom. At different intervals down the screens there are conduits which lead the particles now properly sized into a series of boxes full of water, in which are trays working rapidly up and down. In these the lead separates itself from the matrix by its superior weight and falls to the bottom. There are seven of these jiggers to one rotating sieve, and consequently there are seven different sizes of crushed matrix, and seven different sizes of lead ore deposited. Each of the seven jiggers has three compartments. The material which passes from the first into a box below is clean ore ; and this also is the case to some extent in the second compartment; the third compartment, which contains but little lead ore with other mineral, is re-crushed with a pair of fine rollers, and again goes through a similar process to that above described.
The water passing from the crushers, &c., and containing sludge and slime, is conducted to classifiers by means of launders, as shown in Plate IV. There is a grating or sieve in the launder over the classifier, through which the greatest proportion of the slime water falls, leaving on the grating any substance which may have been carried with it. There is a plug a at the bottom of the classifier, by which the slime is drawn off and allowed to pass to the circular buddles. The slime falls into a cup b and percolates through holes in the bottom into the basin c. Such water as does not fall into the classifier passes on and falls into catch-pits, where the residue of the slime is deposited, and from whence it is lifted and conveyed to other circular buddles.
A stream of clear water flows from a pipe into the receptacle d attached to the revolving shaft e, and, passing downwards, is distributed by means of a tube f projecting through the side of the cup b over the surface of the material deposited from the slime, the water flowing out of the basin c through an aperture g, and being carried away by a launder to the catch-pits. A thin board h is attached to the exterior of the cup b on the side opposite to the projecting tube, and hanging lightly to this board is a piece of rough cloth called a brush. This passes over the surface of the matter deposited and causes the small particles of ore to collect round the centre of the basin, from which it is afterwards collected. The ore is not yet, however, clean enough for market, and has yet to pass through the process of dollying. The dolley tub, a sketch of which is annexed, is filled slowly with the slime ore and water, which is kept in motion by means of the revolving wing to prevent the ore deposit- the tub is full, when until the wing is quickly withdrawn, and two hammers actuated by the same machinery which causes the wing to revolve are set in motion, and, by striking rapid blows on the outside of the tub, assist in causing the ore to be precipitated leaving to the bottom of the tub, leaving the waste, which is of a lighter nature, at the top. From all these processes the production of marketable lead ore is about 250 tons per month. This, after being sampled, is sold to the refiners in the neighbourhood.
The mine is kept free from water by a Cornish pumping-engine, with a 70-inch cylinder and a stroke of 10 feet, beam 32 feet. The water is pumped by a plunger, 21 inches diameter, driven by the weight of the spears, which are lifted by the pressure of the steam. The surplus weight of these spears is taken off by a counterbalance weight, attached to an auxiliary lever or beam. About 558 gallons of water are lifted 53 fathoms per minute. This engine works tip to 250 horse-power and consumes four pounds of coal per horse-power per hour. The valves for the plunger set are Husband's (quadruple) patent. The depth of the winding shaft is 70 fathoms, and levels are driven off at 15, 30, 40, and 50 fathoms.
At Settlingstones the members were conducted over the mine by Mr. F. W. Hall and Mr. Watson. Lead ore has been raised in this neighbourhood for many years. At Settlingstones the vein is visible in the works by the side of the Burn, and bears evident traces of having been worked by the Romans. John Hall commenced working it in 1770, and continued to do so for some years, after which the mine was abandoned, but was re-opened in 1833, by the present proprietors, and it has been worked continually since that time.
The surface works for crushing, separating, and preparing the ores for market, are on the same principle as at Stonecroft, and do not require special description. The water is extracted at Settlingstones by a 60-inch cylinder Cornish engine, a description of which was given by Mr. F. W. Hall, in Vol. XXI. of the Transactions of the Institute, page 59.
For winding there is a condensing engine of 16 horse-power and two of 25 horse-power. One of the shafts is 100, another 75, and another 60 fathoms deep. The barytes is drawn from the workings at from 60, 70, and 80 fathoms lift. Between 2,000 and 3,000 tons of barytes, chiefly in the form of carbonate, are annually produced, and are shipped principally to France and Germany. A little goes to America, and some is used in England for glassmaking and other industrial arts. The chief production of barytes is found in two or three mines in the North of England, and here is one of the principal sources of supply. Almost the entire product of the British Islands is, in fact, within a few miles of this place. The mine is also worked for lead ore. The run of the known veins through the royalty is about a mile and a quarter, and includes. all works in the district. The mines are situated in a very picturesque neighbourhood, close to the Roman AV all, and in the neighbourhood of that portion of the wall where the great discovery was made of Roman coins in the well consecrated to the goddess Coventina, at the Roman camp at Procolitia, on the estate of Mr. John Clayton. A large party of the members visited the shrine, and the whole company afterwards assembled in the village of Newbrough, where they had luncheon provided by Mr. Surtees, innkeeper. Mr. Benson occupied the chair, and various toasts having been proposed, the party proceeded to Fourstones Station, from which place a special train brought them back to Newcastle. The weather throughout the day was exceedingly fine, and the excursion was greatly enjoyed.