The Morenci Open Pit Mine

... THE GREATEST MINING DEVELO MORENCI OP

Using 20th century mining methods, the Phelps Dodge Corporation at Morenci, Arizona is uncovering a mountain that will produce in the next half century some 5,000,000,000 pounds of copper. By electric shovel, huge trucks and trains, 230,000,000 tons of waste material will be removed from the mountain to mine a similar-sized body of ore assaying 1.06 percent copper.

Operations began in 1937, bringing renewed life and vigor to the oldest mining camp in Arizona. A sum estimated at close to $30,000,000 will be expended before full production begins in January, 1942. Foundations for a new smelter, mill and crusher are now being laid. A modern, new townsite has blossomed forth with fine homes for employes. In short, Morenci is one of

PMENT IN THE WORLD TODAY . . . EN PIT MINE

CORPORATION ARIZONA the busiest places in all Copperdom, and the operation there is the greatest mining development being undertaken at this time in the world. Shown here is a general view of the Morenci Open Pit mine. Working benches are fifty feet high. The elevation of the top bench is 5350 feet, the elevation of the lowest bench will be 4200 feet. Preliminary excavations were by electric shovel and truck, to prepare benches for the laying of railroad track for the operation of trains and ore cars. When the mine is in full operation, trains will come from the pit to the right to unload ore for crushing and milling. From the distance the mine looks like a giant ant hill with trucks and trains and shovels scurrying along, but in good and safe order, and by careful, efficient plan.

A working bench at the Morenci Open Pit Mine is a busy place, like the main business corner of a big city. Trucks come and go in methodical fashion, carrying their loads of waste to the dumps. The shovel, like some great monster, never pauses for rest. It represents the triumph of man-directed machine against a mighty mountain.

ARIZONA, according to statistical yardsticks, is the leading copper producer in the nation. Of late, there are some who claim Arizona's laurels will be taken by other states, that Arizona's copper history has been written. For an exciting, new chapter you have to turn to Morenci, where the Phelps Dodge Corporation is spending some $30,000,000.00 in the greatest mining development in the world today. There a mountain is being made into a great open pit mine, from which in the next half cen tury 4,000,000,000 lbs. of copper will be produced. Nothing bigger or more important is taking place in all Copperdom today. Morenci has been a glorious chapter in Arizona copper and if that chapter closed in 1937 the story of Morenci would still hold an illustrious place in the annals of all the copper camps of America. Way back in 1881, a man with vision by the name of William Church first interested Phelps Dodge in the Morenci mining district. Several other companies were operating in that district, all of which eventually merged with Phelps Dodge. So from the '80's until the early '30's of this century, Morenci had been a substantial producer, marking up a total production in its history of 1,800, 000,000 pounds of copper.

annals of all the copper camps of America. Way back in 1881, a man with vision by the name of William Church first interested Phelps Dodge in the Morenci mining district. Several other companies were operating in that district, all of which eventually merged with Phelps Dodge. So from the '80's until the early '30's of this century, Morenci had been a substantial producer, marking up a total production in its history of 1,800, 000,000 pounds of copper.

Eventually the wide, high-grade copper veins in the district played out. Mining operations underground were too costly to handle low-grade ore, until mining geniuses undertook the problem they are now en gaged in-open pit mining. The existence of this vast, low-grade ore body between Morenci and Metcalf was known for many years. Because of the low copper content of its ore, by routine methods of mining it would not be profitable. The first plans for the mining of this low grade disseminated ore body known now as the Morenci open pit were made in 1930. Actual operations began in 1937.

MORENCI MINE

The Phelps Dodge folks at Morenci are transforming a mountain into an open pit mine and by 1942 another Arizona copper producer will be in full operation by Raymond Carlson, Editor, ARIZONA HIGHWAYS Photography by Max Kegley Tentative cost of the development was announced by company of ficials as follows: ad vance stripping, $5,360, 500.00; pit equipment, $5,930,000.00; mill and water supply, $9,450, 000.00; smelter and power plant, $7,100,000.00 and miscellaneous, $919,500.00, with a total estimated out-lay of $28,750,000.00 before one pound of copper could be sold. That is a lot of money to sink into a hillside if you don't know what you are doing. But when you do know what you are doing that is just a safe, wise investment. Needless to say, Phelps Dodge knew what was in the mountain long before it was decided that the mountain could be turned into profitable dollars and cents.

Walter C. Lawson, chief mining engineer for the Phelps Dodge at Morenci, in discussing the open pit mine and its possibi-lities, said in a paper read before the AmThis view of the Morenci mountain was taken by Buehman Studios of Tucson in 1937 before mining op-erations began. This view, com-pared to a view of the mine today, shows the immense amount of work which has taken place.

When benches have been opened by shovel and truck, an intricate network of rails is laid down in preparation for the use of trains in carrying waste longer distances. Note the switchback patterns for favorable grades.

Trains, as well as trucks, are being employed in the removal of overburden at the Morenci mine. This is standard gauge equipment.

American Institute of Mining and Metallur-gical Engineers at the Tucson meeting in November, 1938: "The Morenci deposit that is now being made available by open-pit mining contains copper minerals, principally chalcocite, dis-seminated in porphyry. The ore body has been explored by diamond drilling and un-derground openings and is estimated to contain 284,000,000 tons above milling grade assaying 1.036 per cent copper with rela-tively unimportant amounts of gold and sil-ver. "The mining limits are based on a pit lay-out contemplated to extract about 230,000,-000 tons of ore carrying 1.06 per cent cop-per. This represents a reduction in tonnage through increase in grade cutoff limits and exclusion of portions carrying high stripp-ing ratios. Final pit lines are projected on 45 degrees over-all slopes. "Pit studies of tonnages, copper content

Cars for waste now in use have a capacity of 30 cubic yards, and are of selfdumping, drop-door type. The average waste haul distance will be about two and one-half miles. The terrain of the district, with many deep canyons near the mine, provides ample dumping space.

and overburden showed that the mining of ore is justified through a vertical range of 850 ft., and that the relative elevations of the ore body and the crusher location permit the movement on favorable grades of 85 per cent of all material to be handled. Moreover, in the recovery of this ore it is estimated that 230,000,000 tons of barren or slightly mineralized waste will be removed, making a ratio of 1.00 waste to 1.00 of ore. The average thickness of the capping overlying the ore is 216 ft., with a maximum thickness of 500 feet.

"Obviously, this sort of an ore body requires a large amount of advanced stripping in order to expose sufficient ore for steady mill production. Obvious as well is the necessity for keeping the advanced stripping to minimum requirements, so as to bring the mine to the productive stage without undue capital expenditure."

Forty-two million tons of waste will be removed before pay dirt is reached. The Morenci unit, expected to be one of the largest of the Phelps Dodge producers, will be ready by January 1, 1942, for the production of 25,000 tons of ore daily. When you dig a mine carefully on paper before you dig it on the ground you don't go wrong.

The reason for the development of the open pit method of mining at Morenci is best explained by Mr. Lawson as follows: "The advantages of open pit mining are obvious. First, since all the material within the ultimate boundaries of a pit is handled a little at a time, all the ore can be cleanly separated from the waste, while either dilution of the ore with waste or the recovery of only part of the ore is inherent in most underground methods. Furthermore, it is generally the case that some small zones of mineralization flank the main mineralization and are missed by the big-scale prospecting, but will be exposed and recovered by a stripping operation. These isolated patches of ore are small individually but of appreciable importance in the aggregate, and most likely would forever be unproductive except by shoveling methods."

Also, the low maintenance cost of an open pit is an item of important advantage. During periods of curtailment of production there is little to deteriorate or to be kept in repair-no water to pump and no workings to keep open. Additional advantages are favorable production costs and good flexi-bility. In these days of variable copper demand, the latter feature of a mine is quite desirable since production can be more easily adjusted to the existing requirements."

When you watch the mining operations in effect at the Morenci mine everything functions so smoothly and simply as to be understood by the most untechnical person. The engineering skill, of course, behind the well-ordered plan is another thing.

Of primary success has been the use of a fleet of eighteen 42-ton, 22½ yard trucks. This fleet of trucks together with six 4½ yard electric shovels bore the brunt of early excavations after roads had been built into the mine. As working benches take on a definite outline railroad tracks are put into position and trains have been added to the task of moving overburden. The average haul for the trucks is about 0.6 miles, while the maximum haul is one mile. It is estimated that when the length of haul one is one mile, and a shovel is producing 5000-tons per 8-hour shift, 10 truck units are needed to assure uninterrupted shovel service. The top speed on approximately level grades for trucks, either loaded or empty, is 15 miles an hour. Naturally, operations are planned to afford the most favorable haul-age levels for the trucks. A complete set of pneumatic tires for one truck represents an expenditure of $2,000, while the average life of a set is 12,000 miles. The big trucks approximate 0.8 miles per gallon of gasoline. Recently diesel engines have been installed in some of the trucks, giving unusually efficient service. Each truck comes into the main repair shop for servicing after 32 hours of operation. Considering the importance of the trucks, they receive the treatment of a high-priced race horse. The whole mining operation is so balanced that every cog must render service to perfection in order that the whole schedule is not upset.

tons per 8-hour shift, 10 truck units are need-ed to assure uninterrupted shovel service. The top speed on approximately level grades for trucks, either loaded or empty, is 15 miles an hour. Naturally, operations are planned to afford the most favorable haul-age levels for the trucks. A complete set of pneumatic tires for one truck represents an expenditure of $2,000, while the average life of a set is 12,000 miles. The big trucks approximate 0.8 miles per gallon of gasoline. Recently diesel engines have been installed in some of the trucks, giving unusually ef-ficient service. Each truck comes into the main repair shop for servicing after 32 hours of operation. Considering the im-portance of the trucks, they receive the treatment of a high-priced race horse. The whole mining operation is so balanced that every cog must render service to perfec-tion in order that the whole schedule is not upset.

The efficiency of the trucks depends also upon the efficiency of the shovel crews, which operate the electric shovels after the ground is churn drilled and blasted. Six electric shovels are now in operation at the mine, and they have maintained a production capacity of about 5,000 tons per 8-hour shift. A shovel crew consists of one operator, one oiler and one pitman. The bank ahead of the shovel is sprayed with water to keep the dust down.

Another important machine operating in connection with the shovel and the trucks is the bulldozer. The bulldozer keeps the pit swept up so that trucks can back readily into loading position. A bulldozer operates These nine-inch diameter churn drills play an important part in mining opera-tions at the Morenci mine. They drill blast holes near the edge of the 50 foot banks separating working benches. Ground, thus blasted, is handled by shovels, trucks and trains.

with each shovel and the team work between the two machines adds greatly to the mining operation.

Early this year rail and dump cars were brought into operation at the mine. A net work of standard gauge track has been laid over working benches and a great deal of haulage of overburden is being done by rail.

What was a barren mountain side three years ago now takes on a semblance of an open pit mine with the presence of the tracks along the benches and the pattern of switch-backs from the mine to the mainline lead-ing to the crusher and mill sites. Eventually ore will be hauled by trains to the pit edge over a series of four switchbacks on 4.0% compensated grade for two miles, then on main line track with 0.4% grade for one and one-third miles to the crusher. The average ore haul, when the mine is in production, will be about three miles.

The simple operation of mining when the crusher, the mill and the smelter are in operation is quite apparent. Ore cars will be loaded by electric shovels. Electric locomotives will pull the trains to the main line and will complete the haul of ore to the crusher. Ore will be dumped direct from the ore cars into the primary crusher, from there it goes through the secondary crusher, and then to the mill for treatment. Concentrates will then be transported to the smelter, less than one-quarter mile from the mill, and from there the copper bullion will be loaded into freight cars for refining and fabricating plants. Throughout the entire operation, the machine, art-fully directed by man, becomes the master of the mountain of copper at the Morenci mine.

Stargo is the new residential community built by Phelps Dodge for employes. The houses, modern in every detail, are of four, five and six room design, and are rented to employes for very nominal sums. Approximately 250 homes have been built in Stargo and more will be built as needs for them arise.