Summary:
| Per day. | Per. cu. yd. | |
| Quarrying | $20.10 | $0.37 |
| Crushing | 23.75 | 0.39 |
| ——— | —— | |
| Total for 60 cu. yds. | $43.85 | $0.76 |
The "4 men quarrying" barred out and sledged the stone to sizes that would enter a 9×16-in. jaw crusher. The "6 men wheeling" delivered the stone in wheelbarrows to the crusher platform, the run plank being never longer than 150 ft. Two men fed the stone into the crusher, and a bin-man helped load the wagons from the bin, and kept tally of the loads. The stone was measured loose in the wagons, and it was found that the average load was 1½ cu. yds., weighing 2,400 lbs. per cu. yd. There were 40 wagon loads, or 60 cu. yds. crushed per 10-hr. day, although on some days as high as 75 cu. yds. were crushed. The stone was screened through a rotary screen, 9 ft. long, having three sizes of openings, ½-in., 1¼-in. and 2¼-in. The output was 16% of the smallest size, 24% of the middle size, and 60% of the large size. All tailings over 2½ ins. in size were recrushed.
It will be noticed that the interest on the plant is quite an important item. This is due to the fact that, year in and year out, a quarrying and crushing plant seldom averages more than 100 days actually worked per year, and the total charge for interest must be distributed over these 100 days, and not over 300 days as is so commonly and erroneously done. The cost of stripping the earth off the rock is often considerably in excess of the above given cost, and each case must be estimated separately. Quarry rental or royalty is usually not in excess of 5 cts. per cu. yd., and frequently much less. The dynamite used was 40%, and the cost of electric exploders is included in the cost given. Where a higher quarry face is used the cost of drilling and the cost of explosives per cu. yd. is less. Exclusive of quarry rent and heavy stripping costs, a contractor should be able to quarry and crush limestone or sandstone for not more than 75 cts. per cu. yd., or 62 cts. per ton of 2,000 lbs., wages and conditions being as above given.
The labor cost of erecting bins and installing a 9×16 jaw crusher, elevator, etc., averages about $75, including hauling the plant two or three miles, and dismantling the plant when work is finished.
The following is a record of the cost of crushing stone and cobbles on four jobs at Newton, Mass., in 1891. On jobs A and B the stone was quarried and crushed; on jobs C and D cobblestones were crushed. A 9×15-in. Farrel-Marsondon crusher was used, stone being fed in by two laborers. A rotary screen having ½, 1 and 2½-in. openings delivered the stone into bins having four compartments, the last receiving the "tailings" which had failed to pass through the screen. The broken stone was measured in carts as they left the bin, but several cart loads were weighed, giving the following weights per cubic foot of broken stone:
| —————Size.——————— | ||||
| ½-in. | 1-in. | 2½-ins. | Tailings. | |
| lbs. | lbs. | lbs. | lbs. | |
| Greenish trap rock, "A" | 95.8 | 84.3 | 88.3 | 91.0 |
| Conglomerate, "B" | 101.0 | 87.7 | 94.4 | .... |
| Cobblestones, "C" and "D" | 102.5 | 98.0 | 99.6 | .... |
A one-horse cart held 26 to 28 cu. ft. (average 1 cu. yd.) of broken stone; a two-horse cart, 40 to 42 cu. ft., at the crusher.
| ——————————Job.—————— | ||||
| A. | B. | C. | D. | |
| Hours run | 412 | 144 | 101 | 198 |
| Short tons per hour | 9.0 | 11.2 | 15.7 | 12.1 |
| Cu. yds. per hour | 7.7 | 8.9 | 11.8 | 9.0 |
| Per cent of tailings | 31.8 | 29.3 | 17.5 | 20.5 |
| Per cent of 2½-in. stone | 51.3 | 51.9 | 57.0 | 55.1 |
| Per cent of 1-in. stone | 10.2 | .... | .... | .... |
| Per cent of ½-in. stone or dust | 6.7 | 18.8 | 25.5 | 23.4 |
| ——————————Job.—————— | ||||
| A. | B. | C. | D. | |
| Explosives, coal for drill and repairs | $0.084 | $0.018 | .... | .... |
| Labor steam drilling | 0.092 | .... | .... | .... |
| Labor hand drilling | .... | 0.249 | .... | .... |
| Sharpening tools | 0.069 | 0.023 | .... | .... |
| Sledging stone for crusher | 0.279 | 0.420 | .... | .... |
| Loading carts | 0.098 | 0.127 | .... | $0.144 |
| Carting to crusher | 0.072 | 0.062 | $0.314 | 0.098 |
| Feeding crusher | 0.053 | 0.053 | 0.033 | 0.065 |
| Engineer of crusher | 0.031 | 0.038 | 0.029 | 0.036 |
| Coal for crusher | 0.079 | 0.050 | 0.047 | 0.044 |
| Repairs to crusher | 0.041 | .... | .... | 0.011 |
| Moving portable crusher | .... | 0.023 | .... | 0.019 |
| Watchman ($1.75 a day) | .... | 0.053 | 0.022 | 0.030 |
| ——— | ——— | ——— | ——— | |
| Total cost per cu. yd. | $0.898 | $1.116 | $0.445 | $0.447 |
| Total cost per short ton | 0.745 | 0.885 | 0.330 | 0.372 |