The two important minerals, coal and iron, the circumstances of which have been described in the preceding chapters, are, as has been shewn, closely associated in nature, and limited, so far as their practical extraction is concerned, almost totally to that division of rocks, termed by geologists the coal formation. The numerous other metallic and mineral bodies which are required for the purposes of the arts, must be sought in localities of other and various geological nature; and hence, in order that a proper representation may be given, as well of the actual mineral resources of Ireland, as of the extent to which
On looking over a map of Ireland, it may be observed that towards the coast the surface is occupied for the most part by mountain ranges, whilst the central portion of the island constitutes an almost uniform plane. This diversity of geographical character is accompanied by a difference of geological structure of the most decided character: the mountainous country consisting of the various older or primitive rocks, while the central plain is formed by the limestone, which has been already described as the basis upon which the various tracts of coal formation rest. Almost every district presents in the mineralogical character and arrangement of its rocks, something peculiar in detail which should be described in a work on the geology of Ireland, and on which many important essays have been published by the Geological Society of Dublin; but here such details would be out of place, and I shall only notice the mode of arrangement and constitution of those rocks in a general point of view, and in their principal situations. In the order of formation, which is usually adopted, we may consider the principal rocks found in Ireland, inferior to the carboniferous limestone, to be,
Granite.
Mica-slate.
Clay-slate.
Old red sandstone.
Yellow sandstone.
There are also rocks which do not appear limited to a certain position in the above series, but present themselves accompanying sometimes one, sometimes another member of it; of these are quartz rock, various porphyries, and greenstones. The granite rises from under the other more recently deposited formations, at various points situated mostly along the coast. There are four principal tracts of granite, that of
In addition to these localities there are numerous others where the rock comes up to the surface, only in small patches. This occurs in Tyrone, in Sligo, Fermanagh, Mayo, and Cavan, in Kilkenny, and in several parts of Wexford. These smaller masses, however, are not of any industrial interest.
The rock granite is of complex constitution, being a mixture of various minerals, of which, however, three are so predominant that they are properly considered its characteristic elements. They are quartz, felspar, and mica. The granite of the vicinity of Dublin is distinguished for the whiteness of its felspar and the complete absence of hornblende. The granite of the Mourne Mountains, on the other hand, contains abundance of hornblende, and the felspar is of a flesh red colour. In many places the texture of the rock is so close that it admits of being worked for artificial purposes, and when polished presents a beautiful appearance, from the varied colours and disposition of its constituent minerals. Other varieties are unfit for this use, from
The principal lead mines of Ireland are situated in granite. Copper is also found, but not abundantly. It is the usual receptacle of the ores of tin and of the precious metals. The mines which have been found and worked in the granitic districts, will be hereafter fully described.
Closely associated with the granite, and usually in contact with it, is mica-slate. This rock is not much developed in Leinster, a narrow fringe of it merely edging the granitic district of Wicklow and Wexford. In Donegal and Galway it assumes a more important character. In the former county, by far the greatest part consists of mica-slate, which commencing at the edge of the granite, spreads over the remaining area, and passing into Derry and Tyrone, forms also in these counties the characteristic rock until it disappears under the sandstone formation, which, ranging in a circular sweep from Malin-head to Ballyshannon on the western coast, constitutes its boundary. In Galway a large tract, ranging northward from the granitic district, is formed of mica slate, and this rock occurs extensively also in Mayo, where, although separated by some intervening narrow strips of other rocks, it may be considered as part of the Galway district.
The chemical character of mica-slate is by no means definite
In chemical constitution, mica is very complex, and may yield to the soil, by its decomposition, a greater number of ingredients than almost any other mineral; it contains potash, lime, and magnesia, besides silica, alumina, and often soda. It is a material, however, very little susceptible of decomposition, as is seen by examining a fragment of weathered granite, where the quartz and mica will be found to remain perfectly unaltered, whilst the felspar may have totally rotted away.
The clay-slate which usually rests upon the mica-slate, is one of the most important rocks of Ireland, as well from the area over which is extends, as from the quantity of minerals it includes. The counties of Wexford, Louth, Waterford, Cork, and Kerry, are for the most part constituted of this rock, which, however, appears at the surface in various other localities of less extent. Under the name of clay-slate, there have been, until lately, confounded two formations of very different geological character, and occupying different geographical positions. I shall call them by their simplest titles of lower and upper slate, as these names are least liable to misapprehension. of the lower slate there are two great districts, one north of Dublin, the other south. The northern clay-slate formation commences at Drogheda, and continues along the coast, interrupted only by the granitic protrusion of Carlingford and Mourne, to near Belfast. Inland, its southern edge ranges almost due east and west until it comes near the Shannon at Longford. A line from Belfast to Longford, by Armagh
From Wexford, the clay-slate, intersected by the valley of the Suir, crosses into Waterford, of which county it constitutes a large proportion, extending along the coast to near Dungarvan, and westward to where it is overlaid by the sandstone rocks, which form the crests of the Cummeragh and Monavullagh mountains.
The upper slate, which is distinguished from the lower, not merely by its relative position, but by being found to contain imbedded fossils of specific character, of which traces of primitive organic life the lower slate appears to be nearly destitute, occupies the greater part of the south-west of Kerry, and the adjoining portions of the county of Cork. Its eastern limit is from Dunmanway to near Macroom, whence, stretching towards Mallow, it constitutes the group of the Boghra Mountains, from which the northern edge of the slate district passes due east and west, by Millstreet and Killarney to the Atlantic coast at Doulus Head. The coastward boundary of the upper slate is remarkable for the bold character of its promontories, which, truly peninsular, project far into the ocean, and are separated by the magnificent bays of Bantry and Kenmare.
The peninsula of Dingle consists principally, its western half exclusively, of this upper slate, although it is geographically isolated from the main portion of the rock just noticed, by the interposition of the limestone and of the Munster coal formation, which at Castlemain Haven stretches down to the coast.
In the north of Ireland the upper or silurian slate is found in but one locality, and there developed but to a small extent. It is at Pomeroy in Tyrone, on the edge of the great micaslate district of Derry, from which it is separated by a narrow band of granite. This patch of slate has become of much scientific importance from the study of its peculiar fossils by Captain Portlock, but it does not possess any industrial features that interest us.
I have mentioned that the quartz rock, although not itself possessing a stratified structure, is yet usually associated with those formations of mica-slate and the upper and lower clay-slates, and makes its appearance in great beds or projecting veins, frequently capping the mountain ranges, or isolated hills of the slate districts just now described. The greatest development of quartz rock in Ireland, is in Mayo and in Donegal. In Mayo the northern coast from Erris Head to Bealdarig, consists of quartz, which extends inland to near Lake Carramore, and in the interior, some of the highest mountains, as Nephin, in the interior of the county, are formed of isolated masses of it. Similarly circumstanced are the Binabola (Twelve Pins) mountains in Connemara, which, situated in the midst of mica-slate, consist of quartz.
In the north of Donegal are found vast veins of quartz, from one to three miles broad, more or less interrupted by the adjacent granite and mica-slate, and by the protrusions of greenstone and primitive limestone. The largest and most inland of these veins passes from Cullaff Bay in Innishowen, southwest by Buncrana and Ramelton, crossing Lough Swilly, and finally tapering off at Firtown near Ardara. Its length is about twenty-three miles. From this to the north-eastern coast, several parallel and similar beds occur, of which the highest mountains in the county are composed, as Muckish, from which such excellent sand for technical uses is obtained, and Errigal. The north island of Arran also is formed by a projecting rock of this material.
Proceeding south we meet with quartz in connexion with the clay-slate of Wicklow and Wexford. The peninsula of Howth, and the summits of the Sugarloaf mountains and of Bray Head, which give so much picturesque beauty to the entrance of Dublin Bay, are composed of quartz. In Wexford a great number of isolated hills are capped with it, and the district of Forth consists almost exclusively of this material; this is the most southern point of Ireland in which quartz rock is found.
Resting on the clay-slate, upper and lower, according to its distribution, and occupying, in the geological series, the interval extending from the upper slate to the carboniferous limestone, occur a number of rocks, which occupy a very large portion of the country, and which, being by no means homogeneous, either in their mineral character or their chemical composition, it is very difficult to describe without entering into too much detail. These rocks are usually silicious, the grain varying from the finest sand to large pebbles; they are hence called sandstones, sandstone conglomerates, &c. The silicious material is cemented by a paste, usually aluminous, but more or less coloured by iron, whence the trivial distinctive names, as red or yellow, have been derived. In certain localities the upper beds of this formation are less silicious, and assume a slaty structure, and hence Mr. Griffith, the highest authority on the subject of our local geology, considers, that interposed
The old red sandstone is most extensively developed in the south of Ireland; it forms the greater part of the county of Cork, commencing to the west at the limits of the district of the upper slate, on which it rests, and extending eastwards until it meets the ocean, to which it forms the boundary of Cork and Waterford along the greater portion of this coast. Stretching northwards from Cork, almost to the foot of the Wexford granitic ridge, the mountain ranges of Knockmeldon and Commeragh, and also those of the Galtees, and the Rooley Mountains, are constituted of tins old red sandstone: these mountain groups being only separated by the valleys of the Blackwater and Suir, into which the limestone of the central plain ramifies. The highest portions of these mountains generally show the clay-slate breaking out from under the red sandstone, and illustrating the geological order of superposition, whilst along their flanks, where they emerge from contact with the limestone, a fringe of the more recent yellow sandstone is generally to be traced.
More to the centre, a great number of isolated patches of this sandstone break through the general flatness of the limestone country, especially in Longford and Roscommon; but the greatest development of it, within that district, is in the range of mountains which, under various names of Slieve Boughta, Silvermines, Slieve Bloom, the Arra, Slieve Phelim, &c, occupies considerable area in the counties of Clare, Limerick, and Tipperary, and of the Queen's County, extending north and south from Limerick to near Loughrea, and eastwards to near Mountmellick. The central and highest points of the several portions of these mountains are of clay-slate; the flanks and general mass are old red sandstone, whilst the edge is fringed with the newer or yellow sandstone, on which
Between the mica-slate, clay-slate, and quartz rocks, which form the west of Mayo, and the limestone, is interposed a large tract of old red and yellow sandstone, which from the north coast at Killala, skirts by Loughs Conn and Cullin, and reaches the Atlantic again at Westport. In Tyrone another large field of old red sandstone appears. It extends from near Cookstown to the shores of Lough Erne, about twenty miles, and its breadth is about six miles, marked by Omagh and Ballygawley, which are just on its boundary. Scattered around, and some miles from it, are several smaller patches of the same rock, and of the yellow sandstone, which, however, could not be described without entering too much into detail. This sandstone district may be considered as interposed between the great mica-slate formation of Derry and Donegal, and the more southern limestone country, of which the arms stretch up by Monaghan and Clogher to Coal Island and the basin of Lough Neagh.
The only locality in which the third member of this geological series, the carboniferous slate, is found developed, is on the south-eastern coast of Cork. There it rests on the yellow and red sandstone, and forms a band, of which the usual breadth, as from near Bandon to the old head of Kinsale, is about seven miles, and the greatest length, from Dunmanus Bay to the mouth of Cork harbour, about thirty-four miles. In the promontories of Dunmanus and Skibbereen, the central mountain ridges are of the old red sandstone, on which, at each side near the coast, rests the carboniferous slate: the newer rock, as in most instances, occupying the troughs or more level area between the bolder elevations of those lower in geological order. Several valuable mines of copper, lead, and manganese are situated in this rock.
Already, in the commencement of this work, the general distribution of the limestone rock, and also of the strata of the coal formation which rest upon it, has been noticed; and attention was directed to the great development of the millstone grit, or sandstone of the coal formation, in Leitrim and Roscommon, the circumstances of which, particularly the marine character of its fossils, induce Mr. Griffith to consider it a distinct formation lying between the carboniferous limestone, and the true coal strata. The Connaught coal field would, therefore, require, in a purely geological sense, to be distinguished from the other coal districts which are not connected with the millstone grit formation, but are more recent and superior to it in order of superposition. These considerations are, however, of interest only in philosophical geology; they are not concerned in the practical description of our coal districts given in a preceding chapter, and hence do not require further notice. The limestone strata yield for industrial purposes a great variety of building stones and marbles. The sandstones and conglomerates are used for building, and for millstones. The most important localities for such uses will be hereafter enumerated.
The rocks superior in geological order to the coal formation, are found in Ireland to occupy but a very limited area, being confined almost exclusively to the north-eastern corner of the island, forming the comity of Antrim with some portions of the contiguous counties of Derry and Armagh. In an ascending order the rocks met with in this district are, magnesian limestone, new red sandstone, black shale, lias limestone, green-sand and chalk. These rocks present themselves, however, but on the edges of the district, as the whole is covered with a thick mass of tabular trap (basalt), from which the most characteristic features of the country are derived. Viewed from a distance it appears as a high table land rising from the flat country, or from the sea. Its outline is marked by lofty precipices and barren cliffs, especially along the eastern coast, where masses of black trap from 200 to 300 feet in thickness, often columnar, surmounting precipices of chalk, of dazzling brightness, of 60 or 100 feet high, present a series of objects,
The vast flood of trap and basaltic rocks which overspread this part of Ireland, has, in many cases, so altered the mineral character of the underlying rocks as to render them very unlike the rocks which occupy the same geological position in England. Still they are completely identified by the fossil contents, and in general distribution are as follows.
The magnesian limestone is found but at Hollywood, on the southern side of Belfast Lough. It is a true dolomite, and has been exported to Glasgow to make sulphate of magnesia. In composition it is the same as the dolomites found in various other places in Ireland, of which the more important shall be noticed hereafter.
The new red sandstone, which in England covers so large an area and is of so much industrial importance, from its being the depository of rock salt and of gypsum, is with us but of very limited extent, and is totally destitute of the former valuable mineral. The sandstone, which is usually brownish red, consisting of grains of quartz cemented by a paste, which, though usually argillaceous, is sometimes calcareous, contains much mica, and is often striped with various colours, from decomposition of its ferruginous contents. This sandstone comes to the surface at various points along the edges of the basaltic field; but its principal development is in the valley of the Lagan, which it constitutes from above Moira, by Lisburn to Belfast. Resting on the sandstone are the gypseous marls, which, as a source of plaster of paris, I shall again notice. To these succeed shales and limestones, which are of the formation termed lias, in England, and finally, the chalk, which presents all varieties of hardness, from its usually soft condition, to that of a hard and granular, but beautifully white marble.
Some isolated patches of new red sandstone are found resting on the limestone of the more central districts, and also on the coal district of Tyrone. The coal strata of Monaghan, described pp. 14 and 164, are surmounted by the new red sandstone, and by marls important for a large deposit of gypsum, to which I shall again refer.
Strata of the tertiary epoch are found in Ireland, only at the southern shore of Lough Neagh, where the clays containing wood coal occur. These have been sufficiently noticed in page 29, as a source of fuel.
Finally, the igneous rocks, which, according to differences in minute mineral character and structure, receive the various names of trap, basalt, greenstone, &c, cover over the entire table land of Antrim. These rocks are remarkable for the complexity of their chemical composition and the varieties of imbedded minerals which they contain. They are hence decomposed with great rapidity, and produce ochres and clays of various and beautiful colours, of which beds of great extent occur in Antrim. The soil formed round the edges of this district by the mixture of the decomposing trap and subjacent rocks, is one of the most naturally fertile that is found in Ireland.
Such are the general characters of the geological structure of Ireland. The various groups of rocks differ remarkably in their chemical composition, and consequently are applicable to very diversified uses. Their composition, and also the circumstances under which they have been foxmd, and the agencies to which they have been subjected since their formation, influence materially their mineral contents, and it will be found that the distribution of the several kinds of mineral substances of use in the arts, coincides very closely with the geological arrangement of the rocks. It will be more convenient, however, for the present, to abandon all geological considerations, and merely consider how the several mineral substances of leading interest are circumstanced in Ireland.
The ores of this valuable metal are found distributed throughout the clay-slate districts in a great number of localities, more or less abundantly. In many places the indications are so trifling as not to offer any inducement to enterprize; in others, so abundant as to have given origin to numerous extensive and prosperous mining establishments. The mines of copper at present in practical work, may be conveniently described
Before proceeding to that subject it will be found convenient to remark, that the copper ores most usually found, and which alone become practically of importance, are three in number.
1st. The carbonate of copper, of which there are two kinds, green and blue. The green, or malachite, is not unusual in mines, but occurs only in small quantity. It is very rich in metal, and very easily worked. It consists of carbonic acid, water, and oxide of copper in the following proportions.
| Oxide of copper | 72.07 |
| Carbonic acid | 19.82 |
| Water | 8.11 |
| Total | 100.00 |
This mineral, when pure, possesses a beautiful structure and colour, which renders it very valuable for ornamental uses.
The blue carbonate is still rarer than the green. It is termed azurite. Its composition is,
| Carbonic acid | 25.43 |
| Oxide of copper | 69.36 |
| Water | 5.21 |
| Total | 100.00 |
2nd. The subsulphuret of copper, grey copper ore. This ore is sometimes found very abundantly, and is the most valuable of all the ores of copper. More commonly however it is only found in small pieces mixed with the ordinary ore. It consists of
| Sulphur | 20 |
| Copper | 80 |
| Total | 100.00 |
3rd. The ordinary or yellow copper ore, copper pyrites. This mineral, known by its brilliant golden yellow colour, is a double sulphuret of iron and copper, and contains, when pure,
| Sulphur | 34.78 |
| Copper | 34.78 |
| Iron | 30.44 |
| Total | 100.00 |
In some of the foreign mines the grey sulphuret is the predominant mineral, but in all the Irish, indeed also in all the English mines it is the copper pyrites which forms the material produce, the other ores being but casually found and in very trifling quantity.
The copper pyrites are associated almost universally with iron pyrites, the bi-sulphuret of iron, the peculiar uses of which shall be hereafter specially noticed. The effect of this mixture is to reduce the percentage of copper, which is further depressed by the impossibility of separating even by the most perfect machinery all the adherent rock and veinstone from the ore. Hence copper ore, which contains 12 or 15 per cent. of copper, as sent to market, is considered very rich. The average produce of the copper mines of Cornwall does not exceed 7 per cent. The ore is of course valued according to the quantity of copper which it contains, subject to certain deductions, which it is not here necessary to explain.
Metallic ores are very rarely found disseminated through the general substance of the containing rock, indeed where they are so, they are seldom worth the trouble of extracting. A rock of which the mechanical and chemical structure is uniform, very seldom contains any important quantity of copper or other ores. These occur where a rock has been violently acted upon subsequent to its formation; its strata dislocated and its substance split up by the forcible entry of other kinds of rocks, which, penetrating its mass, form veins, ramifying in various
Such being the circumstances under which metallic ores are usually found, I shall pass to the description of the districts of the copper mines of Ireland.
1st. of the Wicklow District. The principal features of this district have been so accurately described by Mr. Weaver, who was for many years principal conductor of the mines, that I shall do little more than abridge his description, and add thereto such facts as I have been able to collect illustrative of their subsequent progress and their present condition.
The metalliferous clay-slate district occupies but a small space, being very narrow in breadth, and not more than ten miles long, from Croghan Kinshela on the south, towards west Acton on the north.
Metallic substances are diffused throughout the entire space, in slight layers, in cotemporaneous veins, and in massy beds, which last are principally composed of copper pyrites and iron pyrites. The line of the excavations of the works in Connoree and Tigroney extended in 1819 upwards of 1000 fathoms. At various depths in the mass of the clay-slate occur beds of what is technically
Each bed of soft ground contains one or more layers of copper pyrites, or mere iron pyrites, varying in thickness, and sometimes acquiring a breadth of several fathoms. Five of such beds are met with, one in Conoree, two in the old or upper mine of Cronebane, one in the new or lower mine, and one in Tigroney. That in Conoree contains a bed of ore about four feet thick, consisting of a fine-grained intermixture of galena (sulphuret of lead), grey ore (sulphuret of antimony), and blende (sulphuret of zinc), with pyrites of copper, iron, and arsenic. A similar compound occurs in the second bed of the upper mine of Cronebane. The more southern bed contains much iron pyrites, and has yielded at different periods some thousand tons of grey copper ore, which, in the greater depth of the mine, passes into copper pyrites. The third bed, in Cronebane, situated on the western side of the hill, has proved the most valuable, the greater part of its width being occupied by copper ore, which in the upper part consisted principally of grey ore, but at greater depths passed into copper pyrites with iron pyrites. The bed of solid ore has varied from one to three
Beds of iron pyrites, from a few feet to some fathoms in thickness, have appeared in the firm and flinty slate, as in the deep levels of Tigroney and Cronebane. In the flinty slate are found also several cotemporaneous veins of quartz, having rich copper pyrites, accompanied sometimes by azure copper ore, and whose average produce is from 10 to 12 per cent. of copper. These veins range with the slate, ramifying, and where they coalesce, forming a body sometimes twelve feet wide, with four or five feet of solid ore, but they seldom continue productive for more than thirty fathoms in length. Small veins of this description are very numerous.
The mines of Connoree, Cronebane, and Tigroney, so often mentioned above, are situated on the north bank of the Ovoca River. The structure and circumstances of the southern side, on which are the mines of Ballymurtagh and Ballygahan, are precisely similar. It is, therefore, unnecessary to enter on a description, which should be mainly a repetition of what has been already said.
The quantity and value of the ore raised in this district at various periods, may be inferred from the following numbers.
In the twelve years ending 1799, the mines of Cronbane yielded 7533 tons of ore, containing 9 per cent. of copper.
In the twelve years ending 1811, the produce was 19342/3tons, containing 5½ per cent. of copper.
After this period, owing to many conspiring causes, very little ore was raised for many years. Mr. Griffith states, that in 1826 the copper ore raised in Cronbane sold in Swansea for £12,354 14s., and the ore raised at Ballymurtagh sold for £3373. The latter was worked by the Hibernian Mining Company on a single metallic bed, containing copper pyrites with some blende. The lode (vein) at eighty fathoms depth yielded four tons of dressed ore, of 5½
The following tables, illustrative of the actual condition of the mines of this district, have been extracted from the notes of sales at Swansea, and from notices published in the Mining Journal.
The quantities of copper ore from each mine, which was sold at Swansea, and its value, was in 1836:
| Mine | Tons | Value (£ s. d.) |
|---|---|---|
| Ballymurtagh | 4659 | 19,943 12 0 |
| Connoree | 2158 | 10,960 10 0 |
| Cronebane and Tigroney | 4691 | 23,497 10 0 |
| Ballygahan | 305 | 1,417 0 0 |
| Total | 11,813 | 55,818 12 0 |
In 1840:
| Mine | Tons | Value (£ s. d.) |
|---|---|---|
| Ballymurtagh | 3274 | 6,956 2 0 |
| Cronebane and Tigroney | 3017 | 12,889 8 6 |
| Connoree | 158 | 1,250 8 0 |
| Ballygahan | 198 | 346 5 0 |
| 6,647 | 21,442 3 6 |
In 1843:
| Mine | Tons | Value (£ s. d.) |
|---|---|---|
| Ballymurtagh | 1385 | 4,866 19 0 |
| Connoree | 654 | 2,512 0 0 |
| Cronebane and Tigroney | 1160 | 5,438 2 0 |
| Ballygahan | 28 | 100 18 0 |
| 3,227 | 12,917 19 0 |
It would hence appear, that the quantity of ore raised in this district had very much diminished since 1836, but such is not actually the case, on the contrary the activity of industry in those mines, as well as the profits to their undertakers, is, as I understand, steadily on the increase. The quantity of ore sold at Swansea has, however, fallen off very much, as is shewn by the above returns, owing to the copper being now extensively smelted in the neighbourhood of Liverpool, and also to the poorer ores of the Wicklow district being extensively exported to various localities of chemical manufacture, where the sulphur, as well as the copper which they contain, is economized. The true produce of this district at present may be judged by the following table of the ores raised and sold from the Ballymurtagh mine, worked by the Wicklow Copper Mining Company, for which I am indebted to the kindness of Mr. Wright.
In this table is given the quantity of iron pyrites sold by the Company: its price is included in the gross values given.Ballymurtagh, Co. Wicklow
Year Copper ore produced (tons) Iron pyrites produced (tons) Gross value sold at Swansea sold at other ports paid in wages 1840 4839 5334 29596 0 29596 9927 1841 4617 18575 34493 0 34493 16312 1842 7549 9023 29113 1256 27857 15371 1843 6555 8376 24238 5897 18341 10985 Average produce of copper ore, 4½per cent.
Average number of persons employed, 700.W. Hodgson Wright.
It is here seen that the industry of this region has acquired a vast development within the last ten years. This arose from another branch of mining industry coming into play, the trade in iron pyrites as a source of sulphur. In the Wicklow district the copper ore is associated with such vast quantities of iron pyrites, that in order to raise it, it is necessary to quarry the latter to a large amount, which very much enhanced the cost.
It has been seen that by the operations of the Ballymurtagh mine, about £12,000 is annually distributed in wages to about 700 persons. Including the other mines, the total number of persons deriving employment from the mineral industry of the Ovoca district, may be considered as brought up to about two thousand.
2nd. Of the Waterford District.—The geological character of the slate district of Waterford has been already noticed. That part of it which includes the Knockmahon mines, is situated on the sea coast, close to the village of Bonmahon, and extends from the Bay of Dungarvan on the west, to the Bay of Tramore on the east. It has been long known for its mineral treasures: many of the metalliferous veins having been worked by the ancient inhabitants. One almost insulated promontory is perforated like a rabbit burrow, and is known as the Danes' Island; the peasantry attributing these ancient mines, like all other relics of remote civilization, to that enterprizing people. In the abandoned workings antique tools have been found, stone hammers and chisels, and wooden shovels. These workings were easily carried on, as the metalliferous veins presented themselves at the face of the cliffs on the sea shore, and they were abandoned as soon as by the accumulation of water, or an exhaustion of the richer ores, they became difficult to manage.
Within a range of three miles, taking Bonmahon as a centre, a great number of lodes of lead and copper are distinguishable in the cliffs, some of considerable width, but others comparatively small. The direction of the principal lodes is about 20[deg ] south of east, but others vary considerably from this. The principal lodes dip towards the north. The most productive at present in course of working, occur in the clay-slate, although they sometimes penetrate through the strata of other rocks, as hornstone, which are found within the slate. In this hornstone Mr. Holdsworth has remarked the presence
It has been seen already that there is found, in addition to the ordinary clay-slate of this district (Cambrian slate), a small deposit of the superior slate containing fossil remains (silurian), which is found so much developed further south and west. It is, however, here not of practical importance.
In the following letter from Captain Petherick, the Manager of these mines, additional circumstances of their structure, as well as their actual extent and workings are well described:
My dear Sir,—The rock formation in which the metalliferous veins of this district occur is principally clay-slate of a light blue colour, and immediately in contact with the productive part of the vein, it is generally in a softened or partially decomposed state.
The veins are composed of hard compact quartz, intermixed occasionally, particularly where they prove unproductive, with angular fragments of clay-slate; the quartz is the matrix of the ore.
Our principal vein varies in width from six inches to upwards of thirty feet, but its average size is probably from ten to twelve feet: it is, in fact, an unusually large lode; numerous smaller veins also occur on each side of it, some of which have been worked with partial success, but as far as they have yet been explored, they have uniformly become small and unproductive in depth, and at present our operations, with a few trifling exceptions, are exclusively confined to the larger vein.
The mining ground leased to the Mining Company, extends about four miles along the coast, and nearly three miles inland.
Grey sulphuret of copper, native copper, and the red oxide of copper, occur occasionally in the shallow workings, but in comparatively small quantities; the most abundant, and therefore the most remunerative ore, is the yellow pyrites, and in the deeper levels no other kind of ore is met with.
The average percentage of the produce of these mines is 9½ to 10 per cent.
The greatest depth we have yet worked is ahout 800 feet from the surface; and the greatest length of our underground workings is rather more than an English mile, in a direct line.
The number of persons in constant employment in these mines is about 1200; and of that number 140 are females employed in cleaning the ores. No females are ever permitted to go underground.
It is a remarkable characteristic of this district, at least I have never observed it elsewhere, that a part of the vein is composed of a conglomerate of pebbles of quartz and copper, in an indurated clay-paste. Sometimes the fragments of quartz are angular, but more frequently they occur in a rounded state; and occasionally the copper is disseminated in small particles throughout the paste. When I have an opportunity I will take the liberty of sending you a few specimens of the conglomerate, which I am sure will be interesting to you.
Your's, very faithfully,
John Petherick.
The mines of this district, at present working, consist of four groups, which are held by the Mining Company of Ireland from different proprietors. They are, Knockmahon, Kilduane, Bonmahon, and Balinasisla. In the returns of ores sold, these divisions are not distinguished, and hence the following table gives only the agregate produce, and the average value of the entire:
| Year | Tons | Value (£ s. d.) |
|---|---|---|
| 1836 | 3588 | 33,166 0 0 |
| 1840 | 7875 | 63,087 0 0 |
| 1843 | 9101 | 62,956 0 0 |
It is seen by this table how rapidly these mines have been extended by the energies of the Mining Company, under the zealous and skilful direction of Mr. Purdy and Captain Petherick. This extension has been accompanied by some very remarkable; circumstances, to which I shall hereafter direct attention.
The ores are dressed at Knockmahon by very perfect machinery, which is set in motion by overshot wheels, of which one is forty feet diameter and four feet wide; for which there is an ample supply of water. In these operations as well as in mining, employment is given altogether to an average of 1200 persons, whose earnings fluctuate with the produce of the mine. The sum paid by the Mining Company for labour, in this district, is not less than £2500 per month.
3rd. of the south-western District.—The space occupied by the clay-slate formation in the counties of Cork and Kerry, has been found rich in mineral indications; but in many cases where trials have been made, often at very great expense, the result has been unpromising. Of these failures many may be traced to the incompetency or imprudence of the undertakers, but others to the peculiarities in the nature of the ground, which could not have been foreseen. Some mines have been remarkably productive, of which the Allihies mine belonging to Mr. Puxley, and conducted by Captain Read, is an excellent example. Although indications of metalliferous veins have been noticed in all parts of this vast district, it is especially towards its edge, round the sea coast, where it is more or less in contact with, or in the vicinity of, the older slate, or of the old red sandstone, that the more important deposits are found, and hence proceeding from east to west we may trace the series of mining localities of greater or less importance from Skibbereen in Cork, to Kenmare and Killarney.
Between Skibbereen and Skull, at the village of Ballydehob, a vein of copper ore was found of considerable extent upon the surface, and of good produce. This mine was worked with activity for about four years; it gave employment to about 200 persons, and many thousand tons of ore were shipped to Swansea. It was found, however, that according as the workings descended below the surface the lodes became impoverished, and it was ultimately abandoned as unprofitable. It is stated that parties are about to make new trials of this mine.
Ten miles west of Skibbereen, on the property of Lord Audley, are metalliferous veins in great number, on which mines have been opened, known as the Audley mines, and which,
South of the district of the Audley Mines, on the shores of Roaring-water Bay, are situated the mines of Roaring-water, of Cosheen, and of Skull. At Roaring-water the lode is friable quartz and gossan, with bunches of black and grey copper ore. As the workings descend, this passes into rich yellow copper pyrites, which is described as free from iron pyrites. This is a new mine. I do not know that it has yet sent any ore to market. I trust that the indications of rich produce shown upon the surface, may not be found to vanish farther down.
Of the mines of Cosheen and Skull, the former is situated on the shore, the latter on the island of that name. The Cosheen mine was commenced in 1839 by Messrs Connell and McMullen, of Cork. It is advantageously situated on the side of a hill at Skull harbour. A deep adit level has been driven in, just above high water mark, for about 250 fathoms, in the course of the principal lode. This adit drains the mine, and by it the ore is extracted on a railway. The adit is now being driven farther south to cut some parallel lodes which had been superficially explored. The arrangements for working this mine have been made on an extensive scale, under the direction of Mr. Thomas. The number of hands employed is about 130, and I trust, that its proprietors will continue to receive the benefit they deserve, for an enterprize which has brought comfort to a hundred families that had previously no employment.
The ore from these mines, which are but a short time open, was, as given in the Swansea returns:
In 1840, Cosheen, 126 tons, value . . . £1164 2 0
In 1843, Cosheen, 360 tons value . . . £2605 15 0
In 1843, Skull, 84 tons value . . . £134 8 0
The most important mine in this district is that conducted by Captain Read, near Ballydonegan Bay on the west side of the promontory of Bere. The existence of mineral deposits in this locality was first recognized by Colonel Hall, and pointed out by him to the proprietor, Mr. Puxley. The following particulars
This mine was commenced about thirty-three years ago, under the name of the Allihies mine, but as the workings are now removed from the land of Allihies, the name of the Berehaven mine has been adopted for it. In the space of three or four miles are several veins, most of which run east and west, and dip to the north. Some of these were found on trial unproductive and were abandoned, but two veins, one called the Mountain, being situated 450 feet above the level of the sea, on a large east and west lode, the other, the Caminche vein, which runs north-east, have furnished the principal workings.
In the Mountain, a great quantity of copper ore has been raised; there is still obtained about 200 tons per month, of about 10 per cent. produce. The principal working is about 760 feet in length and 852 feet in depth. The lode is sixty feet wide in one place, but branches and narrows in other places to three or four feet. It consists of quartz and copper pyrites. It is all blasted with gunpowder. The deepest levels had been hitherto rather unproductive, but just now, ore of excellent promise has been raised from them.
The Caminche vein is worked for about 570 feet in length and 912 in depth. The engine shaft sinks sixty feet more. The vein runs north-east and dips south-east. It has been very productive; the ore is cleaner than in the Mountain vein; the breadth of the lode is from one to twelve feet. There are employed in these mines about 1000 persons, as
follows:
Miners . . . 400
Smiths and joiners . . . 30
Helpers . . . 25
Labourers . . . 245
Boys . . . 170
Girls . . . 130
Mr. John Read, who is engaged in this mine under the direction of his father, kindly furnished me with the following analysis of the usual quality of ore: he found it composed of
A short distance from these copper veins, is a vein of lead, which was worked some years ago, and some ore raised, but as it did not promise very well, the workings were not proceeded with.
Owing to the conformation of the surrounding country, there is no command of water power at Allihies, and all the machinery for crushing and dressing the ore is driven by steam engines, of which there are five at work.
The ore raised in this mine is about the same quality as at Knockmahon, varying from 10 to 15 per cent. of copper. In the return made to the Railway Commissioners in 1837, the average annual produce is given at from 6000 to 7000 tons, valued at £9 per ton. I find by the returns of sales at Swansea, that the produce was in
| Year | Tons | Value (£ s. d.) |
|---|---|---|
| 1836 | 6418 | 74,879 18 0 |
| 1840 | 4808 | 40,981 2 6 |
| 1843 | 4446 | 36,348 6 0 |
The produce has, therefore, diminished considerably in amount, and still more in richness, but it is to be hoped that this may not continue.
At Holyhill near Bantry, workings have been executed on a vein of copper ore, but are not now in operation.
At Ardtully near Kenmare is a copper mine worked by the Kenmare Mining Association. The produce is the ordinary copper pyrites of moderate richness. The principal shaft has been sunk about twenty fathoms, and the levels extend about sixty. The lode of quartz and calc spar is about five feet wide: it lies at the junction of the clay-slate and limestone. In 1843, there were sold at Swansea from this mine thirty-one tons of ore, which brought £275 18s. The workings of it are as yet
The Lakes of Killarney mark the line of junction of the underlying slate and sandstone rock, with the limestone which fringes the Munster coal field. Along this line, metallic indications have been found in several points, on two of which, mines were opened, which although not now wrought, deserve some notice from the extent to which they were at one time worked, and the peculiar circumstances under which they were abandoned. These localities are Mucruss and Ross Island.
The Mucruss mine was situated near the head of the great lake, by which, and the River Laune, a complete water communication was opened to the sea at Castlemaine. The lode was five feet wide, and was worked at the depth of thirty-six fathoms on the front shaft, and about twenty by another, sunk some distance to the cast. The ore was copper pyrites mixed with much iron pyrites. This mine was worked with great profit from the years 1749 to 1754, but difficulties arising from the circumstances of the European war caused its abandonment. A curious fact in the history of this mine deserves attention. There was found in great profusion a mineral of a granulated metallic appearance, as hard as stone; its colour on the surface dark blue, tending to a beautiful pink. It was not copper ore; it was thrown away as rubbish: no body knew what it was, except one workman, who recognized it to be cobalt ore (arseniuret of cobalt), a mineral of great value, from which the beautiful blue glass and smalt blue is made. This man managed to get away upwards of twenty tons of it as rubbish. Long afterwards a more candid miner, who visited the works and saw some specimens of it, told the proprietor its value; but the deposit of it had been worked out in order to explore for copper, the produce had been thrown away as useless, and it only remained for the mine owner to ruminate on the fortune he might have made, if he had possessed a proper knowledge of his business.
Ross Island, in the great Lake at Killarney, consists of limestone, the metallic lode which passes through it is parallel to
The range of mountains which occupies the north of Tipperary, and forms the gorge of Killaloe, have been found to contain several veins of lead and copper. of these some are now worked: others have been abandoned after trials which were not finally satisfactory. I shall notice these mines but briefly.
These mountains consist of clay-slate, fringed in most places by the old red and by the yellow sandstone, but in others coming directly into contact with the edge of the limestone of the plain. At such a junction is situated Silvermines, deriving its name from old and profitable workings which are now exhausted. A split between the limestone and clay-slate of several fathoms wide at top, and twenty-five fathoms deep, was occupied by soft decomposing clay, with lumps of sand and limestone, cemented by various metallic substances, iron ochre and pyrites, sulphuret and carbonate of lead, sulphuret and carbonate of copper and sulphuret of zinc. Lead was extracted from this mass, and the lead so obtained being unusually rich in silver, gave to the vicinity the name it at present bears.
In the clay-slate tract, south of Silvermines, are several metalliferous veins. In Knockeenroe a powerful vein, consisting of quartz and iron pyrites, with some galena, ranges nearly east and west, and may be traced for a considerable distance, until it sinks under the sandstone which caps the hill. In the latter part of its course it contains copper pyrites. This vein has been examined by Mr. Taylor, who, after some trials, gave it up, and then the Mining Company of Ireland, at the time when the monopoly of the sulphur trade had led to an active demand for iron pyrites, essayed to work through the great mass of sulphur ore, hoping that its sale would enable them to finally ascertain the prospects of copper ore in its interior. It was found, however, that the inland position of the mines, and the refractory nature of the rock, rendered the iron pyrites raised too costly for sale in the English market, and hence the Company was obliged to abandon the investigation without having penetrated through the vast body of sulphur ore which forms the vein. Higher on the mountain, above the junction of the sandstone and clay-slate, are three veins of smaller dimensions, they consist of quartz with sulphate of barytes, and the sulphurets of lead, iron, and zinc.
In the valley of the Newport River are situated the mines of Lackamore. The lode consists of carbonate of lime and iron, bearing rich copper ore in bunches. This mine has been long known and worked. In 1812, when Mr. Weaver wrote, the workings had extended 120 fathoms in length, at a depth of 30 fathoms. After that time they were abandoned, but have been recently brought into activity. There are now about 200 persons employed, and there were sold at Swansea from this mine, in 1840, 111 tons of ore, which produced £1153 7s., and in 1843, 260 tons of ore, which realized £2386 18s.
In the slate district north of Dublin there have been found veins containing ores of copper, which, however, were small and irregular, and have not been found in any case, as yet, profitable to work. At Lough Shinny, near Rush, three veins occur, on which extensive workings have been made, and a good deal of ore raised from time to time, but the operations do not appear to be continuously carried on. On the coast at
In Tyrone, some miles from Dungannon, a number of masses of grey sulphuret of copper have been found, some of considerable size; they were imbedded in a soft vein in the conglomerate resting on the old red sandstone, very near the junction of the two rocks, and were coated with a film of malachite. The geological character of the ground is certainly an unusual one for a connected vein; but trial works are now being executed, and it isto be hoped that the enterprising undertakers may be successful. The ore found is decidedly very rich: specimens of it, which I examined, were pure grey sulphuret, containing 80 per cent. of copper.
Such are the general features of the copper mines that have been, or are now, worked in Ireland, so far as I have been able to discover. Indications of copper have been reported as found in several localities, that I have not noticed, as I ascertained that no real workings had been made, and that the evidence of the importance of the indications did not appear to be of sufficient weight to justify me in inserting them in the present work.
In what has preceded it may he remarked, that I have spoken always of the quantity of copper ore raised in the Irish mines as being indicated by the returns of sales at Swansea. In fact, the facilities afforded in that locality for the economical smelting of metallic ores are so great, that it has become the centre of the Copper trade; and the ores of Cuba, of Cornwall, and of Ireland, mostly converge to South Wales, in order that the metal may be extracted, in estimating the circumstances of any locality where copper ore may be found, the means of conveying it to the shore for exportation, form, therefore, an important element; and fortunately almost all of the districts in Ireland, in which copper mines exist, lie directly on the coast, or near our navigable rivers.
The treatment of the copper pyrites for the extraction of the metal consists in a long series of processes, alternately of an oxidizing and deoxidizing character, which have for their object to remove the sulphur and prevent the reduction of the iron of the whilst the copper may be separated in the metallic state. These processes are altogether usually eight in number, and are performed in reverberatory furnaces, at very high temperatures. Hence the consumption of fuel is very great, and its cost makes up a large proportion of the expense of the operation. I will briefly describe the nature of this process, as it is of considerable interest in a scientific point of view, and then point out the numerical estimate of its cost.
The first object in the smelting process is to roast the ore in a current of air, so that the sulphur may be burned out, and the metals, copper, and iron, may be oxidized. If the ore contain arsenic, or other volatile impurities, they also are driven off. Most of the sulphur passes away as sulphurous acid gas, but some remains as sulphuric acid united with the oxides of iron and of copper. If now this mixture were at once submitted to a reducing action, the metal obtained would be a mixture of iron and copper; this is to he avoided, for such a product would be very intractable and difficult to purify. It is necessary to reduce the copper without, reducing the iron, and for this advantage is taken of the principle that the silicates of the metallic oxides are not reducible by contact with carbon. The quartz, which usually forms the vein-stone in copper mines, remains attached to the particles of ore in such quantity, as generally to constitute half its weight. Now when the roasted ore is subjected to a strong heat, the silica of the quartz unites with the metallic oxides, and Ton us silicates; but as it is wished to form only silicate of iron, the oxide of oopper must be protected, and this is done by adding to the roasted ore, lime, or else a quantity of the slags formed in a subsequent process, and which consist principally of oxide of iron. Hither of these being a stronger base than the oxide of copper, combines with the silica in preference, and there is thus formed a fusible slag containing silicates of lime and iron, and a very
The mass of impure copper thus gotten, and termed matt or coarse metal, is purified by a series of roastings and reductions, which act on the principle that iron is more oxidizable than copper. The matt being melted is oxidized by the air, the iron oxidizes first, and the scoriae of oxide which form on the surface of the molten mass are skimmed off. Sometimes sand is added, which combines with the oxide of iron and prevents any of it from being accidentally reduced by the flame. In this way the iron is gradually all worked out, and the copper assumes the characters by which it is known to be absolutely pure.
These processes are best carried on with an ore which contains from 8 to 10 per cent. of copper, and hence the advantage which a central smelting district like Swansea presents, of enabling the metallurgist to mix together ores of various origin and richness, so as to produce accurately the composition with which his process succeeds best. Thus the poor ores of Wicklow and of Cornwall serve to dilute the richer ores of Cuba, of Berehaven, and Knockmahon. The mixture prepared for smelting, and analysed by Mr. Richard Phillips, consisted of
Copper . . . 9
Iron . . . 20
Sulphur . . . 14
Earthy materials . . . 57
-------------------------------------
100
This had been formed by mixing together equal parts of Cornish ores, of ores from Knockmahon, and of Wicklow ore from Connoree.
The fuel consumed in producing a ton of metallic copper is usually reckoned at from 18 to 20 tons. The value of the ore of course varies with the price of copper, which recently has fallen very much. At 8½ per cent. of metal the weight of ore necessary is 12½ tons, which may be considered as averaging £6 10 s. per ton. The coals cost in Swansea usually 6s per ton,
Mr. Strom has recently directed attention to the great saving of fuel in smelting copper ores by the method followed on the Continent. This consists in roasting the ores in heaps in the open air, and then smelting them in blast furnaces, not unlike the high furnaces of the iron manufacture, but of smaller size. In this manner the fine copper is produced with an expenditure of 13½ tons of coal, almost exactly two-thirds of the quantity consumed in the reverberatory furnaces employed in England. He states also that there is actually a smaller loss of copper during the operation. The money saving by this method should be in Swansea £2, or in Ireland £4 per ton of fine copper, and it is hence a subject well deserving consideration.
In order to complete this sketch of the industrial condition of the copper mines of Ireland, I shall add the following resumé of their produce as compared with that of the English mining district of Cornwall.
The total quantity and value of copper ore from Ireland sold in Swansea were in
| Year | Tons | Value (£ s. d.) |
|---|---|---|
| 1836 | 21,819 | 163,864 10 0 |
| 1840 | 19,580 | 127,910 13 0 |
| 1843 | 17,509 | 117,625 4 0 |
The apparent diminution arises from the causes described in page 178, and which have principally affected the returns of the Wicklow district. The total quantity of copper ore raised in Ireland I believe to approximate, at present, closely to 25,000 tons per annum.
The quantity of copper ore raised in Cornwall was:
| Year | Tons | Value (£ s. d.) |
|---|---|---|
| 1780 | 24,433 | 171,231 |
| 1800 | 55,981 | 550,925 |
| 1820 | 92,672 | 620,347 |
| 1838 | 145,688 | 857,779 |
In little more than half a century the produce of the Cornish mines has been increased six-fold. It remains for us to apply the same energy and perseverance to the development of our mineral resources.
Lead is even more extensively diffused through Ireland than copper, and is found in a much greater variety of rocks, so that I shall not endeavour to trace the distribution of our lead mines in any geological point of view, but describe them in the order of their practical importance, first noticing the constitution of the ores which they usually contain.
That which is pre-eminently called lead ore is the galena or sulphuret of lead. In 100 parts it contains
Lead . . . 86,6
Sulphur . . . 13,4
Its colour is bluish grey; its lustre brilliant metallic; it crystallizes in cubes, and when broken generally forms cubical fragments, but its structure varies very much.
The carbonate of lead, or white lead ore, is occasionally found in quantity, but many mines do not contain it at all. It forms white crystals or masses, which consist of
Lead . . . 77,6
Oxygen . . . 6,0
Carbonic acid . . . 16,4
------------------------------------
100,0
The sulphate of lead is, like the carbonate, white and crystalline, but is distinguished from it by not dissolving in dilute nitric acid. It contains
Lead . . . 68,4
Oxygen . . . 5,3
Sulphuric acid . . . 26,3
------------------------------------
100,0
This ore is of still less frequent occurrence than the carbonate. Both may be considered as only accidentally present, the lead ore, for which a mine is worked, being always the galena.
The granitic district of Dublin and Wicklow is intersected by a great number of veins containing ores of lead; they lie along its eastern boundary, and cross, in an oblique direction, the juncture of the granite with the mica slate. Veins have been worked along this line at Dalkey, and Killiney, on Ballycorus, at Powerscourt, Djouce, Lough Bray, Lough Dan, Glenasane, Glendalough, Glenmalur, and Shillelagh. of these many have been found ultimately unproductive, and the only portions of this district which it is necessary to describe in detail, are those of Glendalough, of Glenmalur, and Ballycorus.
The mountains which enclose the lake and ruins of the Seven Churches, consist of granite, through which run numerous veins of quartz, associated with which are found the ores of lead and in some instances traces of copper. Their general distribution is as follows. At the head of Glenasane, a little above the junction of the granite and mica-slate, a vein of quartz six feet wide, with blende, galena, and some copper pyrites, passes nearly from east to west, and were it continuous would join the vein of Luganure. The latter, the most important in the district, runs altogether in granite. It crosses the mountain Comaderry, and has been accurately traced through a course of 900 fathoms; its ascertained depth being 180 fathoms. This vein is usually five feet wide, but in one place it expands to twelve feet. The principal vein-stone is quartz. The granite in contact with the lower surface of the vein is generally soft and decomposed to a depth of from one to three feet. This vein has yielded, according to Mr. Weaver, in some portions of its course, per cubic fathom, from three to four and a-half tons of galena, which is found either in layers parallel to the walls or in disseminated masses. White lead ore is not uncommon. There are also found sulphuret of zinc, copper pyrites, and phosphate of lead. The produce of this vein usually yielded seventy per cent. of metallic lead. A few fathoms west of this is another vein in the
The Glendalough vein ranges east and west, crossing the glen obliquely. Its course is down the southern flank of Comaderry and it reappears high on the mountain of the opposite side, south of the Waterfall. Its line has been traced for about half a mile, it appears to range far into the granite on the western side, but not to penetrate much into the mica-slate. Its width varies from five to seven fathoms. The great mass of it is quartz. It contains numerous minerals, principally galena, with copper pyrites, sparry iron, and sulphate of barytes. The lead ore of this vein produces 70 per cent., and the copper ore gave from 10 to 15 per cent. of metal. In the Waterfall and ravine at the head of Glendalough are smaller veins, in which lead and copper ores have been found, but on which no workings have been carried on.
On the Luganure vein, and on some smaller veins discovered on both sides of Glenasane, and which are probably outliers from it, a number of shafts have been sunk and very extensive workings made. The old Luganure mine, as well as the Hero mine, have ceased to yield any produce, but the mine of Ripplagh, on the east, and one on the western side of the glen, lately opened at the base of Luganure mountain, are now actively worked by the Mining Company of Ireland, and yield a very fair quantity of ore. They are termed the Luganure Mines. The state of activity of their operations and their amount of produce are shewn by the quantity of dressed ore obtained, which was
In 1842 . . . 675 tons.
In 1843, 547½ tons.
The ore raised is dressed by hand labour and by machinery, to which motion is given by water power derived from the rivulet which passes through the glen. To this Lough-nahagan serves as a copious reservoir, which has been rendered fully available to the purposes of the dressing works. The dressed ore is brought on cars to the Company's smelting works at Ballycorus, where it is worked up along with ores from other sources by
The lead mine situated on the hill of Ballycorus, contains two lead veins, which at the surface are nearly parallel, and cross the junction of the granite and mica-slate, which takes place on the summit. In the workings these veins have been found sometimes to diverge, and at others to coalesce, and were then in every case found to yield valuable bunches of ore. These veins have latterly, however, become unproductive, and although some limited explorations are still canned on by the Mining Company, this mine cannot be reckoned as being at the present time in action. In its vicinity, are situated the Mining Company's smelting works, to which all their lead ores are brought for the purpose of their reduction and manufacture.
On the northern side of Glenmalur where the granite and mica-slate join in Lugduff Mountain, a powerful metalliferous vein presents itself, forming an acute angle with the course of the valley. It has been traced for above 400 fathoms, but probably extends much farther. The vein, as described by Mr. Griffith, is, on an average, fifteen feet thick, and excepting where there are bunches of ore, is divided into five parts. There are three feet of a soft slaty vein containing much talc, then a vein of white quartz, from one to three feet thick, which usually contains ore, next three feet of soft talcy matter similar to the first, then two feet of quartz, in which most of the ore has been found, finally, a third layer of the soft talcy matter extends to the opposite wall of the lode. The lead ore of this mine is considered to be unusually free from zinc and antimony. It has yielded very abundant produce, several large bunches or masses of ore having been met with in the course of the workings. The productiveness has, however, latterly diminished. The number of persons employed on it is at present but about thirty.
On the same and on the opposite side of Glenmalur, several other veins, containing indications of lead, have been discovered, but no serious trials of them have been made.
The clay-slate districts, which have been found so rich in copper, yield also abundant indications of lead, but, up to the present time, few of the mines that have been worked have yielded a profitable return. Of very few of them have there been as yet detailed examinations made, and hence it will be sufficient to notice them succinctly.
At Caime in Wexford, the clay-slate is penetrated by a vein of quartz, ramifying very much, and bearing galena, white lead ore, sulphur et of zinc, with copper and iron pyrites. This vein is of considerable magnitude; at forty-seven fathoms in depth, being twelve feet wide. Several years ago some quantity of copper ore was exported from this mine, and also large quantities of galena, but it was abandoned until a few years back, when its working was resumed by the Mining Company of Ireland, and it is now in profitable activity. The lode is considered to yield about three tons of ore per fathom. The quantity of dressed ore obtained was,
In 1842 . . . 505 tons.
In 1843 . . . 270 tons.
The ore usually contains 75 per cent. of metal, and is sent to Ballycorus to be smelted. The number of hands employed is about 130.
In the clay-slate of the north of Ireland, which spreads over the counties of Louth, Armagh and Down, several lead mines have been opened. In Armagh at Derrynoos, a vein of lead was worked for several years by the Mining Company of Ireland, but finally abandoned. It yielded about 200 tons of dressed ore per annum. It was in this mine that were made the trials of turf as fuel for the steam engine employed in draining, which have been given in a former chapter. At Keady, in the same county, a vein of lead was found, of which Sir Charles Coote, in his Survey of Armagh, speaks in the following words: ‘This mine is on the estate of the College of Dublin, the lands are held by the Earl of Farnham: the late earl expended large sums in sinking and working, but made no profit of it. It is rather wonderful, and indeed proves the value of these mines, that he was not a considerable loser, as he had no active partner to superintend works under ground which he never saw
In Down, at Clonligg, near Newtownards, is a lead mine which is at present worked to a moderate extent. At Dundrum in the same county, a vein containing lead ore has been discovered, and superficial trials of it made.
In the slate districts of the south of Ireland, veins containing lead have been found at Ardmore in Waterford, and in several of the localities already mentioned as the depositories of copper ore. In Kenmare only is the extraction of lead ore at present actually carried on, and the circumstances are so similar to those described in page 186, for the mine of copper of the same place, that it is unnecessary to notice it further. The workings for lead carried on at Silvermines have been also sufficiently described already in page 188. There is nothing doing at present in that locality.
Lead ore has been met with in several localities in the granite and mica-slate district of Connemara, but no workings hitherto entered upon. In the same class of rocks in Donegal, lead veins have been found, and at Kildrum a mine was worked for some time by the Mining Company of Ireland, but it has been given up, and is, I believe, now idle.
The limestone formation affords numerous indications of metallic contents, principally lead: copper pyrites, iron pyrites, and blende, have been found in small quantities, but galena alone has been met with in such quantity as to be profitably worked. The vein stone is usually calcareous spar, accompanied by brown spar. The limestone of the centre of Ireland is, as Mr. Weaver remarks, singularly ill-calculated for the conducting of mining operations. It occupies the lowest and richest part of the country, and frequently supports a great depth of alluvial matter and soil. Hence the drainage of the mines becomes difficult and expensive, and the cost of fuel, and damage to the land, are important. The number of localities in which lead ore has been found in the limestone district is considerable, and some of the deposits have proved of value.
Near Dublin, at Clontarf, a vein of lead ore, accompanied by blende, appeared on the sea shore, where it was wrought until the tide broke in on the workings and the mine became filled up with water. In almost every direction round Dublin small veins of galena have been found in the calp, as at Dolphin's Barn, Castleknock, Kilmainham, &c, but none of them maintained their produce to any depth, or were of a magnitude which would justify any extensive trials.
In the counties of Meath, at Beauparc and Athboy, and of Kilkenny, in several localities, lead ore has been found, but only at Floodhall was a mine ever actually worked. From it considerable profit is said to have been derived, the lead extracted having been very rich in silver. No workings are at present carried on. In Longford, close to the town, lead ore has been raised, and in Kildare, at Wheatfield, on the banks of the Grand Canal, a large deposit of pure galena was found, in connexion with a vein of calcareous and brown spars, on which extensive works were erected, but after some time the store of mineral was exhausted.
The lower limestone of the east of Clare has been found to contain several very large deposits of galena, which have been worked by Mr. Taylor with great success. From bis account of them given to the Geological Society of Dublin, the following is extracted:
Milltown Lead Mine.—The Miltown lead mine in the barony of Tully, in the county of Clare, is probably one of the oldest mines in Ireland. At one time it may be supposed, that there must have been a rich deposit, the ancient excavations being very extensive.
The Royal Irish Mining Company took a lease of it about twelve years ago, but after partially clearing the old workings, and driving a level for a short distance into the north side of the mine, they abandoned the speculation, after raising above eleven tons of ore.
In the year 1836, a grant of this mine was taken from the present proprietors, Anthony Colpoys and George O'Callahan, Esqrs., by John Taylor, Esq. of London, whose name is so well known and deservedly identified with the mining interests of England.
The ancient workings were now completely cleared, and some rude tools discovered, such as oaken shovels and iron picks, the latter of an extraordinary size and weight; also the remains of fires, which had been evidently made use of to crack and loosen the masses of calcareous spar and carbonate of lime, in which the ore of this mine is chiefly imbedded. The spar is very beautiful, being perfectly white, and much of it transparent.
After considerable labour and expense, Mr. Taylor's agents were disappointed in the expectations they had formed of making fresh discoveries of sufficient importance. The works, therefore, were abandoned in April, 1838, after raising forty tons of ore, which, upon an average, yielded about 75 per cent. of lead, and 37 ounces of silver for each ton of ditto.
Within half a mile of this mine, upon the estate of James Moloney, Esq., of Kiltannon, are the celebrated Tomines, or immense natural vaulted passages of limestone, through which the River Ardsullas winds a most extraordinary course. The place is extremely curious, and the stupendous masses of rock forming a gigantic roof over the river, present a scene of magnificence which can never be forgotten by those who have viewed it.
The same river loses itself again among the cavernous strata of limestone rocks near Quin, and afterwards passing-through the picturesque lake of Dromoland, falls into the Fergus, below Castle Fergus.
Kilbricken Lead Mine, in the Barony of Bunratty and Parish of Dura.—In the year 1833, attention was awakened by the circumstance of the accidental discovery of lead ore, by persons in his employment, on the estate of John M'Donnell, Esq., of New Hall, near Ennis.
The first specimens were found by persons while cutting the new line of road between Moriesk and the new town of Clare; after which more important discoveries were made on the farm of Moniuve, by the tenant, John Egan, while cutting a drain through his bog.
The specimens and description of soil and calcareous spar,
in which these stones of ore were discovered, having been submitted to the inspection of Mr. Taylor, in London, he determined on sending agents to examine the district, and in consequence of their report, some experienced miners were despatched from England, through whose exertions about twenty-five tons of lead ore were raised and shipped, which sold at a very high price, being found to assay for lead 76 per cent., and for silver 120 ounces per ton.At this time, however, the rush of water from the surrounding bogs was found to be an insuperable obstacle to further progress, without the aid of machinery, and it was then determined to stay the proceedings until a steam engine of sufficient power to contend against the difficulty, should be despatched from England. This engine was erected and put to work in 1837; operations are now going on upon an extensive scale, and great hopes are entertained of a successful result, but it is too soon to form an accurate opinion upon this point.
This mine is situated within two and a half miles of Quin, and is about six miles from Ennis.
Ballyhickey Lead Mine, in the Parish of Clooney and Barony of Bunratty.—This is the richest lead mine which has been discovered in the county of Clare, and is upon the estate of Hugh Singleton, Esq., of Hazelwood; in a direct line of distance it is about a mile and a half east from Kilbricken, and here lead ore was discovered nearly at the surface. Operations were commenced by Mr. Taylor's agents in the autumn of 1834, and with decisive success, so much so, that an export of 125 tons took place the following spring, and from that period to the present, not less than 2500 tons have been shipped from the port of Clare to the River Dee, averaging by assay, 77 per cent. for lead, and 15 ounces for silver in the ton of lead, and a considerable quantity of ore is still raised and shipped monthly.
The three deposits of ore above mentioned, occur in large veins of calcareous spar which traverse the limestone rock of this country; they differ from any hitherto observed in the mining districts of England and Wales, and indeed upon
the Continent of Europe. The veins of spar are of immense width; in places from twenty to thirty feet, and they run generally a little to the north of east and south of west.The quantities of ore found at Milltown and at Kilbricken are so small, and the masses of spar so large, that it is not easy to trace the intersection of veins or branches at the points of deposit, as distinctly as at Ballyhickey. There the bunch of ore, the richest probably that was ever seen, taking the number of tons raised, and the number of solid fathoms of ground broken into account, occurs upon the intersection of two veins. The main vein runs N. E. and S. W., and its tributary falls in the angle of 45[deg ]. At this point the mass of ore was from sixteen to twenty feet wide, in places, almost pure; in others, raised with sulphate of copper and zinc. The total length of the rich branch was about forty feet, and it is still orey at the depth of eleven fathoms; how deep it may be worth pursuing is a question yet to be solved. The quantity of water is not considerable, although the mine is situated in the middle of a boggy piece of land. An engine, however, has been erected, for the double purpose of grinding the ores, and pumping the water. Fresh intersections of veins are still sought after, being the places at which only other deposits are expected.
The lead ore, as dressed for smelting, usually contains from 60 to 70 per cent. of metallic lead. This is combined with sulphur, and mixed with the material of the associated minerals, principally quartz, and often sulphate of barytes. The mode of extracting the metal is simple: by calcining the ore in a current of air, at a temperature just below redness, the sulphur and metal both become oxidized, and the greater part of the former is expelled as sulphurous acid gas. On then increasing the heat and excluding the air, so that the combustible gases of the fuel act directly on the roasted ore, the oxide of lead formed in the first stage of the process, is reduced, and the metal separates. The smelting is usually carried on in a reverberatory furnace, by which the oxidizing and reducing processes are effected in turn, by regulating the admission of the air. The bed of the furnace is dished, so that the melted
Second. Although, in roasting the ore, the greater part of the sulphur is burned out, yet a quantity of it is converted into sulphuric acid, which unites with oxide of lead and forms sulphate of lead. This is not further changed by calcination, but when the reducing fire is applied, this sulphate of lead, losing all oxygen, would reproduce sulphuret, and thus so much of the material be brought back to its primitive state. To avoid this, the smelter adds to the roasted ore a quantity of lime, which combines with the sulphuric acid and sets free the oxide of lead, which is then perfectly reduced. The lime is also useful in preventing the silica (quartz) present in the ore, from seizing upon oxide of lead and thus producing loss. It takes the silica as it does the sulphuric acid from being a stronger base.
The slags which are formed in this process, consist of the earthy matters of the ore, melted up with the lime which had been added. They also contain a large quantity of lead, so that they are set aside, and being mixed with the material extracted from the flues of the furnace chimney, are smelted in an operation by themselves, and the metal they contain extracted.
Third. A great deal of the success of this mode of smelting depends on a very curious reaction of that part of the ore which has been fully roasted, on that which has not been altered. It will be easily understood, that when sulphuret of lead and oxide of lead are melted together, the sulphur of the one and the
In order to afford an idea of the influence which the cost of the fuel used in the smelting processes exercises on the value of metallic lead, I shall add the numerical results, which have been obtained at Lord Grosvenor's Works at Holywell in Flintshire, and at the Works of the Mining Company of Ireland at Ballycorus, near Dublin.
The ore smelted at Holywell averages 71 per cent. of metal, and is found to yield, by the process above described, in practice, 66 per cent., so that the loss is but 5 per cent. The combustion of coal during the process is half a ton per ton of ore, which amounts to 15 cwt. 17 lb for each ton of metallic lead.
At Ballycorus, where the lead ores from the mines worked by the Mining Company of Ireland are smelted, and the lead wrought into sheet and pipe, litharge and shot, the quantity of ore worked up in the year 1843 was:
From Luganure mines . . . 547½ tons.
From Caime mine . . . 270 tons
Which delivered 10288 pigs of lead, weighing 588 tons 4½ cwt., equivalent to 72 per cent.
The total fuel consumed in the smelting operations was 551 tons of coal and eight tons of coke, making together nineteen cwt. of fuel per ton of lead. The pig lead being now sold at £17 per ton, the coals at 12s., make up 3½ per cent. of the cost of the reduced metal.
The quantity of fuel given, as consumed in smelting the lead at Ballycorus, includes that employed in a process not performed at Holywell, which is the extraction of silver from the metallic lead. This is now practised to a very considerable extent. In noticing the lead mines of Clare, the fact of their yielding silver has been mentioned, and almost all the Irish galenas are argentiferous. So remarkably is this the case, that formerly the lead smelted in Ireland was so hard and brittle, that it was accounted inferior to the English in our own market, and would not be bought, but was sent over to England and to Holland to be refined. This purification consisted in removing from it the silver which it contained, and then it was sent back fitted for its proper uses, and was sold at a higher price. These processes are now all carried on at Ballycorus, and so perfectly as to leave nothing to be desired as to economy of method and purity of product. It is conducted as follows:
The lead having been obtained by the ordinary smelting process, it is remelted, and the concentration of the silver effected by the very ingenious plan invented by Mr. Pattinson. This is founded on the fact that an alloy of lead and silver is more fusible than pure lead. Hence, the lead being melted, is allowed to cool very slowly, until it begins to solidify. What becomes solid contains no silver, and by removing the grains of lead as they form, with a perforated ladle, the silver is concentrated in the portion which remains liquid, so effectually, that ultimately, after several repetitions of the process, the whole quantity of silver is obtained united with about one-tenth of the lead, whilst the remaining nine-tenths of the lead is free from silver and is sent to market.
The rich portion of the lead is then cupelled. A shallow crucible, or capsule, is formed of bone dust and ashes; in this the lead is melted, and then a strong blast from a bellows is blown across its surface; the lead is oxidized, and the oxide
The quantity of silver contained in the lead ores of Ireland, so far as it has been experimentally ascertained, is as follows: The proportions of silver to a ton of lead are generally found to be:
From Luganure mine, Wicklow . . . 3 ounces.
From Caime mine, Wexford . . . 12 ounces.
From Ballyhickey mine, Clare . . . 15 ounces.
From Kilbricken mine, Clare . . . 120 ounces.
From Tollyratty mine, Strangford, Down . . . 10 ounces.
The average produce of silver extracted from the lead ores of the mines worked by the Mining Company of Ireland during 1843 was seven ounces and a half to the ton of lead, and the total quantity was 4261 ounces, which sold for £1157 10s. 8d.