Tools and Machinery of the Granite Industry

Chronicle of the Early American Industries Association, Inc., The, Jun 2006 by Wood, Paul

Removal of Overburden

The first task in the development of most quarries is the removal of the overburden or waste materials that usually cover at least a part of a proposed quarry site. These waste materials might include soil, boulders, and low-quality granite. Blasting with dynamite might be required to free some of the waste and to reduce it to manageable size. At first, removal was a manual operation assisted by ox or horse. An ox shovel would be used to drag waste to the edges of the quarry site. A manually loaded ox cart might be used to carry the waste greater distances. The waste removal operation reached a new level of efficiency with the introduction of the stripping cableway with self-filling bucket (Figure 15). The cable extended across the quarry site and beyond. The scoop filled with waste as it was dragged across the surface and was automatically dumped at one side, out of the way of future quarry operations. Piling of grout on top of good granite was a costly lack of foresight. The cableway with skip, or grout box, was also used for the removal of overburden. The skip was filled with waste and automatically dumped onto waste piles at the quarry edge (Figure 16). Often, the cableway that was initially used for stripping was later used during quarrying operations for the removal of grout and small quarry blocks. Today, grout is usually not piled but rather backfilled on marginal land not likely to be used for future quarrying.

Drilling Deep Holes and Lift Holes

Slate splits easily into sheets along cleavage planes. Marble and limestone can also be split relatively easily by the use of wedges. Granite is the hardest stone and the most difficult to split, but these two characteristics vary among the granites. For example, Barre, Vermont, granite is a harder stone and more difficult to split than Woodbury, Vermont, granite. Bethel, Vermont, granite drills harder and breaks harder than Barre granite. Even though granite is a much more difficult stone to split, it does have an easiest plane of splitting called the rift. Perpendicular to the rift is a plane of" next easiest splitting called the lift or grain. Perpendicular to both these planes is a third plane of most difficult splitting called the hard way or head grain. Typically, the quarry block face (the front) and back are the hard way, the sides are the rift, and the top and bottom are the lift. Granite quarries are configured as a staircase of benches (the "steps"), each bench being typically twenty feet high and twenty feet deep and hundreds of feet in length. The first block extracted from the bench is called the keyway block (see Figure 14) and is often difficult to remove due to the sideways compressive forces that build up in granite deposits. After the keyway block is removed, the two adjacent blocks with three exposed surfaces are removed and so forth in both directions down the bench.

Two types of holes were drilled-vertical deep holes forming the sides and back of the quarry block to be extracted and horizontal lift holes forming the bottom of the block. These lines of holes were indicated with marking chalk, which was usually blue or red in half-globe cakes or square blocks, by the head quarryman. The holes were typically one and one-quarter inches in diameter, twenty feet deep, and spaced six inches on center. This resulted in a cube-shaped quarry block twenty feet on a side weighing about 680 tons (Figure 17). Initially, quarry drilling was a manual operation using a hand drill and drilling hammer (Figures 18 and 19). For the deep holes, one quarryman held the drill and one (called single jacking) or two (double jacking) quarrymen swung the drilling hammers with the drill-holding quarryman rotating the drill slightly after each blow (Figure 20). It is believed that the terms single and double jacking came from "Cousin Jack," a nickname for a Cornish miner. The drilling hammer had two beveled-edge striking faces and weighed three to four-and-a-half pounds. Hand drills came in graduated lengths and had either a star-shaped or flattened cutting head. Periodically, a deep hole mud spoon (Figure 21) was used to clean the powdered granite from the hole. For the lift holes, either a granite surface was available for the quarryman to stand on or scaffolding was erected on the face just below the intended line of drilled holes (Figure 22). The quarryman held and rotated the drill as well as swung the drilling hammer. In a Michigan hand drilling contest, a double jacking team drilled a fifty-nine-and-one-half-inch deep hole in Vermont granite in fifteen minutes. In a Colorado contest, a quarryman single-handedly drilled a twentysix and five-eighths-inch deep hole in Colorado granite in fifteen minutes.