Plato Malozemoff, president of the Newmont Mining Corporation, this morning personally directed pouring of the first ingots of full-production gold at the Carlin Gold Mine, as dignitaries from Elko, Nevada, the federal government, Newmont, and other affiliated interests, observed.
Newsmen from leading journals throughout the nation were also on hand.
At a press briefing last night at the Stockmen’s Motor Hotel, Malozemoff revealed the hitherto secret fact that the Carlin Gold Mine ore is averaging 0.32 ounces of gold to the ton, or $11 per ton. Production will claim more than 90 per cent of the gold in the ore.
Robert Fulton, vice president of Newmont, said the orebody has so far been mapped out to contain 11 million tons of ore; or enough to keep the mine and mill operating at its 2,000 ton per day capacity for just less than 15 years. Beyond that, mapping is not complete, although Fulton said the end of the orebody has not yet been found.
Newmont’s operation is the first major gold strike to be made in the past 35 years. Malozemoff noted that, 35 years ago, the operation would have required three times the men it does today, because of advances since then in mechanization.
The Carlin Gold Mine, with about 76 employes, will produce about one-seventh the annual U.S. gold production with 200,000 ounces, coming from the mill. Only the Homestake mine at Lead, S.D., produces more, at 500,000 ounces per year. Two Canadian mines are larger making Carlin the fourth largest in North America.
Fulton said his studies of the orebody reveal it dates back to the Paleozoic age for formation of the host rock. The gold itself dates to the Terciary period of the earth’s development. He noted there is a remarkable association of barite in the ore, and said it is their hunch that the two mineral are not too far apart in age.
Frank McQuiston, Newmont vice president and designer of the Carlin operation, said the gold is in siltstone — “mud when its wet,” but the recovery of gold through cyanidization is hampered by the slime formation. Special filtration and floculation systems were designed, including radioactive systems, to clear the solution so the gold could be precipitated out.
McQuistion noted that Carlin is the only cold-climate operation using outdoor thickener tanks and the first of its size to be constructed in as short a time as ten months.
Construction began before the drawings were complete, McQuiston said, with the Bechtel Corporation in charge of mill construction.
Bob Hernlund, vice president of Newmont who headed up the engineering, said several unique problems in gold mining were presented by the ore, and unique solutions were found.
The gold is so fine, it can only be seen under 1,800 power magnification, and then only the larger particles are photographable. These “larger” particles are two millionths of a square inch in size, he said. In order to successfully assay the ore, Newmont had to adapt the Australian system of atomic absorption spectrophy, the only North American operation using this system. Fire assaying by methods over a hundred years old were not satisfactory for extremely fine, low grade ore.
Bob Denny, Newmont vice president in charge of engineering for automation and mechanization, said the plant was designed with three control points.
Radiation from cesium is used for control throughout the plant, he said, with little or no danger to workmen from the radioactivity present because of shielding.
All critical items were started up for production on the automatic setup, with no manual beginnings, so that there would be no possibilities of error or failure showing up later, he said.
Fulton noted that Isbell Construction Company, holders of the original stripping contract, removed 2.5 million tons of earth prior to the start of the operation. Howard and Crawford is now continuing the overburden stripping.
A 3 1/2-yard electric shovel loads the dump trucks with ore or overburden, which then moves to its proper destination.
Malozemoff said the mill represents a $6 million investment, the tailings dam another $1 million, and the overburden removal prior to operation another $3 million, for a total investment of $10 million before the first ingot was poured early this month during the shake-down period.
Newmont footed the investment alone, with no loans, stock promotion, or other methods, and will recover the investment in the first five years of operation, Malozemoff noted.
