TIPPERARY GEOLOGY

Samuel Lewis

1837

The mineral productions are various and important. The plain country forms part of the great limestone field of Ireland. The Roscrea and Devil's Bit mountains, which are a continuation of the Slievebloom range, consist of sandstone in mass, whose covering everywhere assumes the form of conglomerate: the Keeper and Bilboa mountains, in which this range terminates, consist of a nucleus of clay-slate surrounded by sandstone, except on the north, near the village of Silvermines, where the clay-slate comes immediately in contact with the limestone of the flat district, extending nearly to Lough Derg: the surrounding sandstone in some parts forms a red coarse conglomerate, similar to that of Lyons and Donabate, near Dublin, and is quarried for mill-stones.

The Galtees, with the subordinate ridge of Slieve-na-muck, consist wholly of sandstone, the upper part of which forms strata from "one to two feet thick, gradually curving in the form of the summit: the sandstone of Slieve-na-muck is arranged in horizontal strata, which yield excellent flags. The Knockmeledown and Monavullagh mountains, ranging along the southern boundary of the county, are likewise composed of clay-slate, with sandstone at the base and horizontal strata of the same formation on their summits: the Slieve-na-man group is of analogous structure, consisting of a nucleus of clay-slate surrounded and surmounted by sandstone, which is connected with the sandstone hills stretching by Nine-mile-house towards Carrick-on-Suir and Thomastown. The clay-slate to the east of Slieve-na-man, extending towards Kilmagany, yields good slates, particularly in the quarries of Inchinagloch, or the Ormond quarries.

The Killenaule coal district chiefly occupies a low range of heights extending to Coalbrook, on the north-east, a distance of about 5 miles. The strata constituting this formation are shale and sandstone, the principal bed of the latter forming the main body of the elevated part of the coal hills; the whole occupy a depression in the limestone strata, from the borders of which they dip to a common centre, those declining from the northwest having a descent about twice as rapid as those from the south-eastern margin. This bed of sandstone forms narrow troughs or basins lying north-east and south-west, in which are beds of fire-clay, forming the immediate floor of the coal and covered next it by two beds of shale and one of iron rock. In some instances this series appears to be repeated, two or more seams of coal lying one above the other in the same trough, which are generally from 40 to 43 yards from the surface to the upper bed of coal, with a breadth of from 500 to 700 yards.

The fire-clay under the coal varies in thickness from four to nine feet, and is everywhere interspersed with vegetable impressions, apparently of grasses, which, when fresh, have a glossy surface. The roof also exhibits vegetable impressions of a similar kind, chiefly of ferns, reeds and grasses, but occasionally of shells. The coal of the whole district is of the kind called stone or blind coal, similar to that of Kilkenny and Queen's county. The value of the quantity annually raised, previously to 1825, amounted to about £12,000, but has since nearly doubled. The increase is attributable in a great measure to the exertions of the Mining Company of Ireland, who took several of the mines on lease, among which were those of Glangoole, Ballygalavan, and Boulintlea, the last-named of which is said to be the most extensive coalfield in Ireland, and opened that of Mardyke in 1827.

The principal colliery worked by an individual is that of Coalbrook, the property of Mr. Langley, in which the beds of coal are not only more extended but nearer the surface and more regularly stratified than any others in the same . neighbourhood: a singular feature in the strata of these collieries is their occasional interruption by what are technically called "hags" or "faults," which consist of substitutions of firm shale in lieu of coal, commonly from three to five yards broad, ranging across the troughs in a north-western and south-eastern direction. The Coalbrook colliery has been worked for more than a century by the family of the present proprietor, and was the only mine of any importance kept open previously to the Mining Company's undertaking: the first steam-engine in this part of the country was erected in it.

There are now extensive collieries in full operation at Ballinastick and Earl's Hill, belonging to Mr. Going. The troughs generally contain two or three seams of coal from one to two feet thick, covering a space varying from 50 to 600 acres. The undulating surface being favourable to the construction of adit levels, most of the seams were worked to the depth at which this mode was available before much use was made of steam power. One fourth of the produce of the seam is pure coal and the remainder culm: the former is peculiarly adapted to every purpose where a strong regular heat is required; it possesses about 87 per cent, of pure carbon, and, therefore, without any preliminary preparation, it is fit for the use of the maltster, and is carried to great distances for brewers, distillers, millers, and smiths: the culm is in great demand for burning lime, and is likewise made up into balls with a mixture of clay, and used in the kitchen: the charge for the coal at the pit's mouth varies from 20s. to 40s. per ton, according to the quality; that of the culm from 16s. to 18s.

The collieries in which steam-engines are employed are worked on the most approved principles, the engine pits being sunk in the lowest part of the field whence the coal is raised: eight engines are now erected in the district, in which 34 pits are at work, giving employment to upwards of 1000 persons. In the Coalbrook pits several valuable seams of iron stone, yielding about 30 per cent, of metal, have been found, which have not yet been turned to profitable account.

The Mining Company likewise possesses extensive slate quarries in the hilly tract adjoining the lower extremity of Lough Derg. Until a late period the produce of these quarries had to be conveyed by a land carriage of six miles to Killaloe, whence it was taken by boats along the Shannon or canal, although they lie within two miles of the Shannon navigation; but a new line of road thither, and the erection of a small quay in a bay in Lough Derg, allow it now to be conveyed at a greatly reduced scale of carriage to every part of the country with which the Shannon or the canals communicate.

The produce of the mine has been about 7000 tons annually. The same company had the slate quarries at Derry, close to the shipping quay on the Shannon, but these are, now held by John Salmon, of Derryville, near Killaloe, Esq.; and also those at Glenpatrick, east of Clonmel, of great magnitude and returning a good profit. But the mineral works of earliest celebrity are the copper and lead mines near Silvermines. They were first worked by an English company who extracted a considerable proportion of silver from the ore; when their lease expired about a century ago, new veins were opened and the works extended in different directions by successive companies. Mr. Hudson, the last lessee, sold his interest to the Mining Company, who, after sinking some expensive shafts, relinquished the attempt.

The works were opened in four places called the Old Works, Knockeen, and Kevestown, on Lord Dunally's estate, and Garryard, on that of Lord Norbury. The Old Works were carried on in a space between the clay-slate and limestone rock, which here approach each other, being several fathoms wide at the surface, but contracting until it closes at the depth of about 25 fathoms. This was filled with clay, sand, decomposed slate, and scattered blocks of limestone, lydian stone, and hornstone; the whole mass being penetrated and cemented by metallic deposits, consisting of iron ochre in various stages of induration, iron pyrites, white lead ore, galena, malachite (the value of which was unknown and it was therefore thrown away), copper pyrites, with calcareous spar and heavy spar.

In Knockenroe is a powerful vein, consisting at the surface principally of quartz and iron pyrites, with some heavy spar, galena, blende, and copper pyrites. In Knockeen are various others, comprising the same substances. About five miles to the east of Newport is the old copper mine of Lackamore, the workings of which were very extensive, and an attempt was made to renew them at the beginning of the present century, but was abandoned on account of the insufficiency of the machinery to draw off the water.

It was subsequently worked by the Mining Company, and yielded ores worth from £20 to £30 per ton, but has again been abandoned as unprofitable. Here are two veins running through clay-slate, and composed of brown spar, calcareous spar, clay, and iron ochre, more or less indurated, a few inches in width; and a third vein of the same material, but of greater thickness, and comprising rich copper ore in bunches at Cappaghwhite, Ballysinode, and Gurtdrum, in this county: these were also held on lease by the Mining Company, who seem, however, to have made no attempt to work the two first, but on the last they made an outlay, in 1826, of £300, apparently without any return. Ores of zinc and manganese are common in various places, but no efforts are now being made to work them.

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