QUARRY (Fr, carriere). When any useful rock is worked in an open manner at the surface of the earth, the excavation is called a quarry. Quarrying differs little from mining in principle, except that the latter is essentially an underground operation.
From a very remote period, famous granite quarries have been worked at Syene, and others of sandstone and limestone, along the banks of the Nile, for the temples and monuments of ancient Egypt. Greece found the materials for her white marble temples in the quarries of mount Pentelicus, near Athens, and in those of the islands of the archi pelago. It was from the quarries of travertine (a kind of limestone), at Tibur, that ancient Rome was chiefly built. Italy has long been celebrated for her marble quarries, those of Tuscany yielding the most esteemed kinds. The fine saccharoid marbles for statuary and other fine-art purposes are exclusively obtained from the Apuan Alps, rise around Carrara, 'Massa, and Seravezza. Those of Carrara, especially, are highly prized all over the world. From the quarries at Seravezza, marble to the value of £130,000 has been taken for the splendid cathedral of St. Isaac at St. Petersburg alone.
Of the more celebrated quarries of the British islands, we may mention those of Corn wall, Aberdeen, and Wicklow for granite; those in the neighborhood of Edinburgh, Glasgow, and Newcastle for sandstone; those near Bristol and Doncaster, and in the isle of Portland, for limestone; those of Derbyshire, Devonshire, Kilkenny, and Galway for marbles; and those of north Wales and Argyleshire for slates.
To understand the operations of the quarryman, it is necessary to bear in mind that all rocks belong to one or other of two great classes, namely, the stratified and the unstrati fied. The former are sedimentary rocks, occurring in parallel beds or strata, and consist chiefly, in so far as we are at present concerned, of sandstone and limestone. Unstrati fied or igneous rocks, which include greenstone or whinstone, granite, porphyry, etc., have no distinct bedding, that is, they do not lie in seperate layers. Roofing-slate is a stratified rock, but it splits into thinner iaminw in the direction of its cleavage than in the direction of its bedding, the former being often at right angles to the latter. Granite and other igneous rocks have also a natural jointage or cleavage, although they are not stratified. Advantage is taken of these peculiarities in quarrying the different rocks, but in the main the systems adopted do not greatly differ.
Stones are most frequently separated from their native rock by blasting with gun powder. This operation is described in detail under BLAsTrxo; see also GALVANISM and SAFETY-FUSE. Of late the practice of boring juniper-holes with engine-power has been introduced, and wherever it can be conveniently applied, must be a great improvement 'on the slow and tedious process of boring by hand. See TUNNEL.
With some stratified rocks, such as sandstone, a good many of the best stones are procured without the aid of gunpowder. Hand-tools are alone used, because blasting is apt to cause rents, and otherwise- shatter portions which it is desirable to keep solid. this method, the quarryman makes a number of small holes with a pick, along a cer tain length of rock, into which steel wedges are inserted. After a succession of blows with heavyhammcrs, the wedges at length cut through the stratum. Blocks for columns, obelisks, tombstones, etc., are best procured in this way. It may also be stated. that arc obtained from those more valuable parts of sandstone deposits technically termed "liver rock;" which consist of the thicker and more consolidated strata. Flag stones and other pieces of limited thickness are quarried from the thinner beds termed "bed rock." When stones are removed in masses by blasting or otherwise, they have still to be quarried into shape, according to the purpose for which the various pieces are best suited. Thus, in an ordinary building-stone quarry, the larger stones (after those of unusual size and quality are selected for the purposes named above) are roughly formed into ashlar; window-sills, lintels, rybats, corners, steps, and the like, by means of such tools as picks, hammers of various kinds, and wedges. The small irregular-shaped pieces are called rubble, and are used for the commonest kind of building. Slates are split up into the thickness used for roofing, by means of a mallet and broad chisel. In granite quarries worked for paving-stones, as has been incidentally alluded t") above, the loss of material in reducing the blocks to the size and shape required, is enormous, as much as four-fifths of the whole being commonly wasted. Besides the tools already mentioned, long iron bars called pinches, and pbwertul cranes for turning and lifting the larger stones, are nearly all the implements required by the quarry-master.
In quarrying, as well as in mining, much of the cost is incurred for the pumping of water from the workings. A good steam-engine and set of pumps arc, therefore, indis pensable fur every quarry of any extent. Much expense is also every now and then incurred in clearing away sand, gravel, and other loose debris from the upper bed of the rock. This, which is called "drift" by geologists, and "tieing" in some localities by quarrymen, often becomes suddenly very deep, especially where the beds dip at a high angle, and is an obstacle by which many quarries of stratified rock are sooner or later arrested.