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Hillside Fluor Spar Mines, on the 350-foot level (June, 1922) the vein filling was largely calcite with occasional small veins and pockets of fluorspar. The distance between the vein walls does not seem to change much with increasing depth.

At some levels both walls are limestone; at others one wall is limestone and the other sandstone or shale. In general the footwall is firm, clean, and solid, whereas the hanging wall is more often irregular and tends to be weak. In some places little or no timber is required to support the walls, though timber is used to support the broken ore in the stopes; in other places the walls require heavy timbering.

Perhaps the greatest single problem in mining ore from the Rosiclare vein is the handling of the large quantity of water which flows into the mines through open channels in the limestone. At its southern end the vein is cut by the Ohio River, and most of the mine workings are well below the river level. The principal mines have been flooded repeatedly, especially in spring, causing long delays and involving great expense for dewatering. The mining companies have had to build heavy bulkheads and install expensive pumping equipment, and the cost of pumping excessive quantities of water from the increasing depths is one of the largest items in production cost. It has been estimated that under normal water conditions at one of the largest mines 164 tons of water must be pumped for each ton of fluorspar produced.

As mining methods and many general features of production are similar in the largest mines on the Rosiclare vein, a detailed description will be given of the method of one company only. An extended description of at least one mine is included, to give an adequate idea of the operation of a typical mine.

Fairview Fluorspar & Lead Co. (now Franklin Fluorspar Co.).—The property of the Fairview Fluorspar & Lead Co. (now the Franklin Fluorspar Co.) extends from the Ohio River on the southwest to the property line of the Rosiclare Lead & Fluorspar Mining Co. to the northeast, and contains about 4,800 feet of the Rosiclare vein outcrop. It also contains an unknown length of the Blue Diggings vein (possibly an extension of the Daisy vein of the Rosiclare Lead & Fluorspar Mining Co.) and an unknown length of the Golconda fault, now known to be mineralized.

The Rosiclare vein is opened in three distinct sections, not connected underground. The principal shafts in each section are: (1) The Extension and Annex shafts; (2) the Good Hope shaft; and (3) the No. 4 shaft. Only the first two sections have been worked in recent years. The mill is located in the central section, near the Good Hope shaft.

When the property was acquired by the Fairview Co. (about 1900) all operations were being conducted on a small and inefficient scale. Improvements and changes were gradually made, and in 1907-1908 production began on a large scale.

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The ore body in the Good Hope mine varies from a tight pinch to 25 feet in width, and in the Extension mine from a pinch to 20 feet, but it is somewhat more uniform than in the Good Hope mine. Shafts. The Good Hope shaft is sunk in the footwall 6 feet from the vein at the surface and 120 feet from the vein at the 473foot level. It is a timbered shaft with 3 compartments, 2 skipways and 1 pipe and ladderway, cut 6 by 16 feet down to the 80-foot level and 5 by 16 feet from there to the bottom (about 500 feet).

At the Extension shaft the vein is practically vertical and both the Extension and the Annex shafts are sunk in the hanging wall, the former about 30 feet from the vein and the latter about 85 feet from the vein. The Extension shaft is cut 5 by 16 feet from the surface to the 165-foot level and 5 by 14 feet from there to the bottom (400-foot level). The Annex shaft is cut 6 by 16 feet and is 300 feet deep. Both are timbered shafts and the compartments are arranged as in the Good Hope shaft.

The No. 4 shaft and the Blue Diggings shaft have not been used in the past few years.

Underground development.-The Good Hope shaft is mined by levels at the following vertical distances below the surface: 70, 145, 212, 281, 343, 400, and 473 feet. The Extension shaft is opened at the 90, 200, 300, and 400 foot levels; the 200-foot level practically corresponds to the 212-foot level of the Good Hope shaft, but the two lack about 150 feet of being connected.

Shaft stations are cut on the main levels, and at some levels ore pockets or skip-loading bins are excavated below the shaft stations. These bins may hold 50 to 500 tons each of broken ore. Near the shaft stations on various levels pump rooms, sumps, mule stables, powder magazines, and so on are cut.

As the Good Hope shaft is so near the vein at the surface, a 50foot shaft pillar has been left in the vein on each side of the line of the shaft. About 200 feet south of the Good Hope shaft is an air shaft from the 70-foot level to the surface.

The main drifts are cut 9 feet high by 7 feet wide, or the width of the vein if it is over 7 feet, and on a grade toward the shaft of from 0.5 to 1.0 per cent. The grade of the drift bottom depends upon the volume of water to be handled in the drainage ditches cut on one side of the track. The unusual drift height of 9 feet is carried through the ore-bearing parts of the vein, for the stopes are started directly from the backs of the drifts. Usually no drift

timbers are needed for support and nearly all wood used underground has some connection with actual mining. Through pinches or barren parts of the vein the drifts are cut somewhat smaller. Waste produced in drifting is dumped down into old empty stopes if possible; otherwise it is hoisted to the surface. The main drifts are usually kept at least 100 feet in advance of the stopes.

Mining methods.-In general the method of mining used is shrinkage stoping over stulls. The details of the method are about as follows:

After the main drifts have been advanced far enough stoping is started. Stopes are 100 to 1,000 feet in length, depending upon local conditions. In starting a stope a horizontal slice about 5 feet thick is removed by overhand stoping along the back of the drift, making the total height of the drift about 14 feet. Drilling is done. from wooden horses or temporary working poles (light stulls) set across the drift.

Heavy stulls are next set along the drift on about 5-foot centers, at a height of about 6 feet on the footwall side and usually about 9 feet on the hanging-wall side, depending upon the width of the vein and the dip. Ore chutes with gates are built between alternate sets of stulls (chutes thus on 10-foot centers) and the spaces between chutes tightly lagged over with poles. Stopes are set off or separated from each other by bulkheads composed of a line of stulls lagged over on the stope side. Between stopes two such sets of stulls are placed and lagged, leaving a manway between to give access to the stopes and aid natural ventilation.

After the chutes and gates have been placed, stoping is started. Holes are drilled in the back with compressed-air stoping drills and the ore shot down. After each shot only enough ore is drawn off from the chutes below to leave working room in the stope for drilling the next round of holes. The back of the stope and the level of the broken ore in the stope are kept at about uniform levels; that is, one part of the stope is not worked out at a much faster rate than another part.

Stoping is continued upward to the level above, or a horizontal pillar or "arch" is left to support the drift above. If the ore is wide it is often loose and weak; then it is entirely removed and replaced by a row of stulls to carry the track in the drift above. "Arches" or drift pillars range from 5 to 20 feet in thickness, depending upon local conditions. Level intervals are normally 100 feet vertically, but additional levels are sometimes opened halfway between.

Waste is left standing in place if possible, but small blocks of waste must often be shot down with the ore and later removed in

milling. In places the hanging wall is weak and loose slabs are found. These are caught up by stulls and left in place.

When the stope is finished and the final drawing off of the ore is started miners stay on the gradually lowering top of the broken ore, dressing down the walls and supporting them with stulls as necessary. After the ore is completely withdrawn, the stulls over the drift below are double lagged with poles, covering the chutes and the interspaces. Wall rock is then shot down to load the stulls, to protect them from later falls of rock, and to make a more or less air-tight carrier to assist ventilation.

Haulage. The ore is drawn off from the stopes into hopperbottom steel cars that hold about 20 cubic feet or approximately 1 ton each. These cars are hauled by mule or gasoline locomotive to the ore pocket at the shaft station. At the Extension mine the gasoline locomotive used will pull 10 loaded cars. The empties are spotted at the chutes by mules. If there is a loading pocket at the shaft station the ore is dumped from the cars over a heavy grizzly with bars set about 6 inches apart, and sledged through into the ore pocket. At levels where there is no ore pocket the grizzly is set over the top of a raise cut through from an ore pocket on a level below, and the ore is dropped to the lower level for hoisting. Usually part of the ore pocket is divided off to form a separate compartment for waste, which otherwise is handled the

same as ore.

Hoisting. From the ore pockets the ore is drawn off directly into skips of 11⁄2 tons capacity and hoisted to the surface. The Good Hope shaft is equipped with a 10 by 14 inch hoist; the Extension shaft with a 122 by 15 inch hoist (for ore and waste); and the Annex shaft with a 9 by 12 inch hoist (for men and timber); all are steam-driven double-drum friction hoists, coupled solid and used in balance.

At the Good Hope shaft the skips dump directly into a 100-ton mill bin. At the Extension shaft the ore is dumped into a 150-ton storage bin, from which it is drawn off into standard-gauge hopperbottom cars, hauled to the mill, and dumped through a chute into an underground mill bin cut from rock about 80 feet below the surface and holding about 250 tons. From this bin the ore is hoisted in skips to the top of the mill. A total of 225 to 250 tons of ore can be hoisted per day from the two mines if two 8-hour shifts are worked.

Drainage and pumping.—As noted before, the drainage problem is very important in this district. Large sumps are cut near the shaft on each level (for example, one sump in the Good Hope shaft is 50 feet long, 10 feet wide, and 10 feet deep), and the water from

the workings flows to the sump through drainage ditches along the sides of the drifts. As much water as possible is caught on the upper levels and is sometimes piped to the nearest sump below.

At the Good Hope shaft about 1,500 to 1,800 gallons of water are usually pumped to the surface per minute; at the Extension shaft about 1,300 to 1,500 gallons per minute. In unusually wet seasons these amounts may be nearly doubled.

At the Good Hope mine all pumping is now done from the 473foot level, the present bottom level, where three steam pumps with a total capacity of 3,300 gallons per minute are installed. Two pumps (1,200 and 800 gallon capacities) are of the compound, duplex, outside, end-packed, condensing type with pet valves. The other pump is a three-stage turbine-driven centrifugal.

At the Extension mine on the 200-foot level are two noncondensing steam pumps with a total capacity of 1,500 gallons per minute; on the 300-foot level are three steam pumps with a total capacity of 2,500 gallons per minute. The exhaust steam of all pumps is discharged into the sumps.

For many years the pumps were drowned when the mines were flooded and dewatering with sinker pumps was very slow and costly. A few years ago bulkheads were built to protect pump rooms from flooding. The most elaborate bulkhead is installed on the 473-foot level of the Good Hope mine. The sketch, Figure 23, shows the general construction. Figure 24 shows the face of the bulkhead and details of the door.

This bulkhead is 15 feet thick and is wedge shaped, with the larger end toward the source of the underground stream. It has a very heavy cast-steel door, which may be quickly and tightly closed in case of flood. Through the bulkhead are run pipes, with valves on the pump-room side. When the mine is flooded the water may be drawn off through these pipes as rapidly as the pumps can handle it. Before this equipment was installed dewatering sometimes took six months; now it can be done in about 10 days.

The mine water is slightly alkaline and does not corrode pipes or pumps.

Drilling and blasting.-Nearly all types of compressed-air drills have been used here, but certain types are now more or less standard. For drifting, pneumatic-feed hollow-steel water stopers are used for the top holes and light rotating hammer drills (jackhammer type) for the toe holes; regular column or bar-mounted hammer drills of various sizes and types may be used for both classes of holes. For stoping, various makes of pneumatic-feed stoping drills are used, usually dry. All drill steel is hollow and hexagonal in section and usually has the ordinary cruciform bit. Sometimes, however,

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