QUARRY, QUARRYING (OF. quarriere, Pr. carriere, from ML. quadraria, quarry, place where stones are squared, from Lat. quadratus, p.p. of quadrare, to square). The open excava tion from which any useful stone is taken for building and engineering purposes is called a quarry; the operations required to obtain rock in useful form from a quarry is called quarrying. Quarrying processes are three in number, viz. by hand tools, by explosives, and by channeling and wedging. 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, occur rying in parallel beds or strata, and consist chiefly, in so far as we are at present concerned, of sandstone and limestone. Unstratified or Igneous rocks, which include greenstone or whin stone, granite, and porphyry, have no distinct bedding, that is, they do not lie in separate lay ers. Roofing-slate is a stratified rock, but it splits into thinner lamina' 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.
Hand tools alone may he successfully used for quarrying stone which exists in beds. The principal hand tools are the pick, the crowbar, the drill, hammer, wedge and plug, and feathers. With the drill and hand hammer a row of holes a few inches apart is drilled partly through the layer or stratum, perpendicular to its plane of stratification and along the line at which it is desired to break the stone. These holes are usually drilled from in. to 3 in. in diameter. In each hole are placed a plug and two feathers. The plug is a narrow wedge with plane faces; the feathers are wedges flat on one side and rounded on the Other. When a plug is placed between two feathers the three together will slip into a cylindrical hole, and by driving the plug down between the feathers it exerts a splitting or cleav ing force of great intensity. In quarrying, as
first stated, each hole in a long row is filled with a plug and feathers; by striking each plug a sharp blow with a hammer, hitting them in suc cession, and by repeating the operation again and again, the combined splitting force of the plugs and feathers finally becomes great enough to rup ture the rock. Generally the plugs and feathers are used only to• effecting the larger subdivisions of the rock, the smaller pieces being split and broken by hammers and wedges. Sometimes this method of quarrying is called the plug and feather method.
Explosives are the means most commonly em ployed for detaching large blocks of stone in quarries, these blocks being afterwards split and broken into smaller stones by wedges or by the plug and feather method. In this method of .quarrying the drill holes are put down to the depth to which it is required to break the rock and are then partly filled with some explosive, which is discharged by the usual methods of blasting (q.v.). The kind of explosive used depends upon the character of the result which is sought. In quarrying rock to he crushed into small fragments for road work, concrete making, etc., the object sought is a rather finely broken mass of stone, and here, because of its great shattering effect, some form of high explo sive, as dynamite, is employed. When building stone of large size is to be quarried, weaker and slower acting explosives, as gunpowder, are em ployed. In each quarry the structure of the rock has to be carefully studied with the view of taking advantage of the cleavage planes and natural joints, and for each class of rocks there is a characteristic method employed. The drill boles are usually made by rock drills operated by power. though band drills and churn drills are also used. The drill holes are driven vertically in a row some distance back of and parallel to the edge of the working face of the quarry, and are blasted simultaneously so as to force outward a rectangular mass of rock.