"The following sketch of the history and activities of the United Verde Copper Company, of Jerome, is written by C. E. Mills, chief engineer, for the 'Yavapai' magazine. The United Verde mine is one of the world's most famous copper properties. Volumes would be exhausted in the story of the mine's development during the past half a century. An idea of the magnitude of the enterprise is given in the sketch of Engineer Mills."
"The United Verde mine, at Jerome, Arizona, was first located in 1876, and worked intermittently until 1888, when Senator Clark, of Montana, obtained an option on the property and purchased control in 1889. From 1900 to June 1, 1928, the United Verde produced 15,034,880 tons of ore, which yielded 717,354 tons of copper, 22,798,906 ounces of silver, and 648,087 ounces of gold."
"The United Verde mine employs 1,300 men at Jerome, this number being distributed as follows: mine department, 830; shovel department, 180; mechanical department, 180; office and miscellaneous, 110."
"The present production rate is 10,000,000 pounds of copper monthly, or 130,000 tons of ore. Approximately one half of this tonnage comes from the shovel pit, and the balance from underground operations. The gold and silver value of the ore is considerable, as show by the production record since 1900."
"ORE DEPOSITS: The main sulphide mass consists of a huge pipe-like body, extending from the surface to the lowest levels and dipping steeply to the northwest. This mineralization was aided by the concave margin of the United Verde Diorite which forms the hanging wall of the pyrite mass. The footwall is either black schist or altered quartz porphyry."
"The commercial ore bodies occur either along the iron-schist contact, with occasional replacements of the schistose quartz porphyry, or within the pyrite mass itself. On the upper levels the ore zone is approximately 600 x 100 feet, and lenticular in shape. On the lower levels the mineralization is confined more closely to the iron-schist contact, and the ore bodies extend approximately 1,000 feet along the contact and vary from a few feet to 250 feet in width."
"EXTENT OF DEVELOPMENT: Underground operations extend from the 300 level at an elevation of 5207 feet, to the 8000 level, at an elevation of 2528 feet. The mine is served by two shafts: No. 5 shaft extends from the 3000 level to the 800 level, and is used exclusively for hoisting ore from all levels below the 900 level. No.6 shaft is a service shaft, and extends from the 400 level to the 3000 level. Both shafts are of reinforced concrete and steel construction, and have underground hoist rooms. The mine is developed by approximately 50 miles of workings, all of which are accessible and open."
"FIRE ZONE: The upper portion of the mine has been on fire since 1894 and, up to 1916, a small tonnage of ore was mined from the fire stopes. The fire area is bulkheaded off to prevent air from entering and aiding combustion, so that the active fire area does not extend below the 700 level."
"Early, in 1919, a steam shovel program was started to uncover the fire areas and make available some 5,000,000 tons of ore. The open pit will extend to the 500 level, but does not include all ores at this horizon. In order to cool the rock within the fire area and permit mining of underground ores outside of the pit limits, a 200-ton sliming plant has recently been completed to furnish slimes for extinguishing these fires."
"The slime plant consists of an 18 inch by 24 inch Blake crusher, 54 inch by 24 inch Allis-Chalmers rolls, a 36 inch by 8 feet Hardings ball mill, with the necessary bins and conveyors. The plant has a capacity of 15 tons per hour, and produces a product averaging 55% solids, 35% of which will pass through 150-mesh screen. A mill hole with bulldozing chamber at the south side of the pit is the source of muck, which is transported to the mill by 30 cubic foot rocker bottom cars."
"The slime is delivered to the mine through a 4 inch standard wrought iron pipe with 3 inch branches. It is forced into the fire stopes either through concrete bulkheads or 2 and one half inch diamond drill holes provided for this purpose. To date approximately 40,000 tons of solids have been used, and it is expected that this program will extend over a period of several years before the temperatures are sufficiently reduced to permit resumption of underground mining operations."
"SHOVEL MINING: The shovel program was started in 1919, and the stripping operations involved the removal of approximately 7,000,000 cubic yards of waste rock from above the 160 level in 8 major benches. The first bench was 110 feet high, and the others averaged 50 feet in height. Eleven miles of switchbacks connected the various benches and provided dump track for the disposal of waste. The breaking of this waste was done by churn drills, rock drills, and coyote mining, and the disposal was effected by steam shovels, 80-ton locomotives, and 25-yard side dump cars. this work was completed in October, 1927."
"Shoveling operations below the 160-level are carried on by 30-foot benches; No. 4 cut is now being mined and is at the same elevation as the 300 level."
"All ores and waste are passed down through raises to the 1000 level, where the ore is handled through Hopewell Tunnel in the same way as underground ores. There are 6 classes of muck, each of which must be handles separately, viz., direct smelting, mill ore, leaching ore, converter, low grade iron, and waste."
"Flexibility of operations is absolutely necessary in clean mining these various classes of ores, and for these operating conditions small shovels and motor tracks have been found most suitable."
"Shovel equipment consists of four Bucyrus 50-B electric shovels. These are equipped with caterpillars, and have a 1-3/4 yard dipper, and weigh 60 tons. Track equipment consists of ten Moreland TXL, 6-wheel 10-ton trucks, and six Linn tractor trucks. Bodies are of special design, holding 5 cubic yards, and dump by gravity."
"The shovels handle on an average 1000 tons per eight hour shift, although record runs of as high as 2000 tons have been made. Three trucks usually serve one shovel, the average haul being 500 feet. At present two shovels are being operated on all three shifts."
"Armstrong electric churn drills are used where the ground is uniform, whereas machine drilling and blasting is used in inaccessible places, in hard ground, in mining along contacts, and in trimming banks. Churn drills use a 6-inch bit, and are cased in fractured ground. In hot ground the holes are cooled with water prior to loading with 35% or 50% gelatin. Some of the rock drilled has a temperature of 400 degrees Fahrenheit. If the holes cannot be cooled to 120 degrees F., they are fired by torpedoes, which consist of a sheet metal tube lined with asbestos and filled with gelatin cartridges."
"Machine drill holes are sprung and loaded with 35% gelatin, and detonated with No. 8 electric blasting caps. In hot ground it is impossible to cool machine drill holes with water, and torpedoes are made from 1 and one-half inch cardboard mailing tubes."
"LEACHING: Low grade ore from the shovel pit is transported to Hopewell portal, where it is spread on dumps arranged for leaching operations. Mine water is run over these dumps and by chemical action the copper is oxidized and dissolved by the percolating waters in the form of copper sulphate. This water is then run over scrap iron laid on shallow wooden flumes, and the copper solutions replace the scrap iron and precipitates as metallic copper. Approximately 350,000 tons of ore averaging 1.5 per cent copper is now being treated in this way, with a monthly production of 30 tons of 80 per cent precipitates."
"UNDERGROUND MINING OPERATIONS: The underground mine furnishes 65,000 tons of ore per month. Eighty-four percent of this is hoisted through No. 5 shaft to the 300 level, where it is dumped into the ore bins leading to Hopewell Tunnel; the remaining 16 per cent comes from the upper portion of the mine and is handled by gravity."
"Seven different mining methods are used in the extraction of this tonnage, and are listed as follows: Horizontal cut and fill, 54.2 per cent; Incline cut and fill, 5.7 per cent; Square set, 16.6 per cent; Incline square set, 3.4 per cent; Top slice, 19 per cent; Shrinkage, 1 per cent; Underhand cut and fill, .1 per cent; Total, 100 per cent."
"The general conditions governing the selection of a mining method are the size and shape of the ore body, grade and character of the ore, character of the walls, and cost of materials. Other important considerations are the necessity for safe and efficient working conditions for the men, fire hazard, complete extraction of ore, flexibility of stope development, and ease of sorting waste. The best mining method for any block of ground is the one which will give the lowest total cost per pound of copper with the greatest amount of safety for the men. Each block of ground is considered as a problem in itself, and a method of mining selected or developed as will best suit the particular block of ore to be mined."
"HAULAGE AND TRANSPORTATION: The ore from the stopes is bulldozed or broken to pass an 11 inch grizzley provided on top of each chute. the muck in the stopes is shoveled directly into the chutes for distances up to 15 feet. For greater distances wheelbarrows or 20 cubic foot scoop cars are used, with 18 pound sectional steel track. Mechanical loaders of various kinds have been tried out, and at present the 3-drum electric slusher is proving successful."
"The ore from the chutes below the stopes is pulled into 30 cubic foot rocker bottom cars and transported to No. 5 shaft grizzley pockets. A train consists of 16 cars, and is hauled by 6-ton Jeffrey trolley locomotives or 5-ton Westinghouse storage battery locomotives."
"The shaft pockets hold 500 tons and load into 7-ton pockets or cartridges, which in turn empty into the 7-ton skip. The gates are operated by air cylinders. A special crew of skip loaders working on bonus become quite proficient in operating these pockets, the average loading time being but 7 seconds per skip."
"As stated before, the skips dump automatically into a hopper or selector, which is controlled electrically by the hoist operator and may be moved to dump into any one of three bins, depending on the class of ore hoisted. The ores from the shovel pit are also dropped to the 1000-level bins. Hopewell Tunnel is 7000 feet in length, and 9 x 11 feet in section. The ore from these loading bins, also the excess waste from the pit, is transported to Hopewell transfer bins by 40-ton bottom dump Koppel standard gauge cars. Baldwin-Westinghouse 25-ton trolley locomotives handle a 9-car train at a speed of 7 miles per hour."
"From the outside transfer bins the various classes of ore or waste are handled to the dumps at Hopewell or loaded into 60-ton cars and transported to the smelter at Clarkdale over the Verde Tunnel and Smelter Railroad."
"DEVELOPEMNT: In order to maintain an underground production of 2500 tons per day, it is necessary to sink at the rate of 150 feet per year and to do 1800 feet of drilling and raising each month. In laying out development work, it is essential to know the character of the ground, location of ore, and geological formations. To facilitate the locating of ore limits and geological contacts, approximately 6000 feet of diamond drilling is done each month."
"VENTILATION: A well ventilated mine is essential for efficient working conditions. The standard aimed at in providing air to the various working places is to keep the temperature between 75 and 80 degrees F., relative humidity not over 80 per cent, velocity 125 to 250 feet per minute, and a volume of 250 to 350 cubic feet per minute per man. Ventilation also serves to cool the rock temperatures which increase at the rate of one degree for each 150 feet in depth. It also serves as a means of carrying off gases and dust caused by blasting."
"At the United Verde mine many thousands of dollars have been spent in improving the ventilation system. A large 4 foot 6 inch x 9 foot Jeffrey, double inlet fan, with a capacity of 250,000 cubic feet per minute is located on the 1000 level. Fresh air is drawn from the surface through a fire proof raise 13 x 13 feet in section. From the fan the air is forced down through an air raise which extends to the bottom levels of the mine. Small electric blowers and compressed air jets are used for secondary ventilation with galvanized iron or canvas tubing."
"TECHNICAL DEPARTMENTS: All labor underground and on the surface is carried on a contract or bonus system. the setting of standards and the clerical work in connection with the figuring of bonus and contracts is handled by the Bonus Department which employs 8 men."
"Both underground and shovel pit sampling is absolutely essential in mining to the proper limits, and preventing dilution. This work is performed by 6 samplers. A fully equipped assay office is located on the 300-level, and handles both mine and pit samples. A average of 10,000 samples are taken and analyzed each month."
"The engineering and geological departments employ 20 men. These men do the necessary engineering and geological work required in an enterprise of this magnitude."
"The safety work in any mine is very important and although this work is in charge of one engineer, all bosses and foremen are directly responsible for the safety of their men. Every precaution is taken to eliminate dangers and hazards at this mine and no expense is spared in making working conditions safe."
"MINE SURFACE PLANT: The mine shops are located on the 500 level, and are connected to the No. 6 service shaft by an audit 1800 feet in length, equipped with standard and 18 inch gauge track. The shops are of brick and steel construction and represent an expenditure of one and one half million dollars. They consist of a compressor house, sub-station, machine shops, warehouse, boiler shop, blacksmith shop, drill sharpening shop, pipe shop, drill repair shop, electric shop, change room and time office, and other miscellaneous buildings."
"The lumber yard and framing shed are also located here. Some 9,000,000 board feet of timber and lumber are used each year at the Jerome plant."
"All shops are equipped with the most modern equipment. The drill sharpening shop is of particular interest. Here 2000 pieces of drill steel are sharpened and heat treated daily. All furnaces are equipped with pyrometers to give exact heat control necessary for uniform steel. Approximately 140 tons of drill steel are used each year."
"WELFARE WORK: The United Verde Copper Company has improved living conditions at Jerome greatly during the past few years, and have provided facilities which go toward making a better mining camp. Among these may be listed the following: 1. A building program involving the construction of 78 houses and the development of a new townsite at a total cost of $322,000. 2. Construction of a new modern hospital involving an expenditure of $272,000. 3. Construction of a new employees' clubhouse costing $40,000. 4. Construction of 2 swimming pools fitted with the best equipment, at a total expenditure of $17,500. 5. A community park was constructed on a waste dump close to the town of Jerome. This included grass plots and playground equipment, and represents an expenditure of $26,000."
"All workmen are not only protected by state compensation, but the United Verde Copper Company has taken out group insurance which protects a workman and his family against death, permanent and temporary disability. The company pays half the cost of the premiums and the workmen pay the other half."
"The generous policy of the United Verde with regard to its employees, together with the bonus and contract system of labor, has done a great deal toward making Jerome one of the best mining camps in the state."
(Verde Copper News; Friday, March 15, 1929; pages 1 and 2.)