History of the Carlin Trend

History of the Carlin Trend

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CARLIN — On May 4, 1965, with little fanfare, Newmont poured its first bar of gold from the Carlin Mine. The pomp and circumstance of the official commissioning of the mine would have to wait a few more weeks. That first bar marked the start of one of the largest and longest-lived mining districts in the world.

In summer 1961, geologists John Livermore and Alan Coope arrived in Carlin to visit the Blue Star mine and the Gold Quarry prospect. Livermore had recently heard a talk by U.S. Geological Survey geologist Ralph Roberts about an area in northern Eureka County that had the potential for hosting gold deposits. The type of deposit they were searching for was similar to Getchell, Gold Acres and Bootstrap, deposits in which the gold was dispersed as microscopic particles that could not be found using a gold pan. After visiting and examining the local deposits, Livermore and Coope began exploring an area approximately 2¾ miles south of Blue Star on Popovich Hill. They postulated that gold would be found in the limestone rocks below a regional fault known as the Roberts Mountains Thrust.

Drilling on the project began in 1962 and on the third hole intersected 100 feet of mineralization averaging 1.03 ounces of gold per ton, marking the discovery of what would become the Carlin Mine. Drilling to outline the orebody progressed quickly and by the end of 1963 had identified 11 million tons of ore averaging 0.300 ounces of gold per ton, a grade sufficient for mining when gold was selling for $35 per ounce. Construction of the mine and mill began in 1964.

Production ramped up quickly, peaking at 337,000 ounces in 1967 and delivering the millionth ounce in 1968. Between 1968 and 1980, production from Carlin began a slow decline, reaching a low in 1980 of 110,000 ounces — the same year that gold hit a high price of $800 per ounce. In 1971, the government had quit fixing the price of gold, allowing it to rise based on market conditions. This higher gold price allowed Newmont to acquire the Blue Star and Bootstrap mines in 1972.

Early mining in the Carlin pit focused on the oxide ore, all of which was fed to the Carlin Mill, now referred to as Mill No. 1. Early drilling, however, had shown that gold also occurred in refractory ore containing carbon, which had the undesired tendency to “rob” the gold particles out of the cyanide solution used to leach the oxide ore. In 1971, Newmont added a flash chlorination process to Mill No. 1 to treat the carbon-laden ore.

As the price of gold rose, lower-grade ore could be mined. But due to the high cost of milling, another new process was needed. Newmont’s first leach pad was built at the Bootstrap Mine in 1979. In 1981, Newmont commissioned another leaching operation at the Maggie Creek deposit, using asphalt pads on which the ore was placed and leached before being removed.

Discoveries of new deposits proliferated in the 1980s. The decade kicked off with the 1980 discoveries of Gold Quarry and Rain, followed by Genesis in 1984. During subsequent years in the 1980s, 16 new deposits or major extensions of existing mines were found. In 1987, Newmont’s production from the Carlin Trend reached 5 million ounces and continued delivering about 1.5 million more ounces each year afterward by the end of the decade.

A significant milestone that helped speed up development of the Carlin Trend was the 1982 purchase of the T Lazy S Ranch (known today as the “TS Ranch”) from Litton Industries founders Charles Thornton and Roy Ash. This purchase suddenly enabled Newmont to begin exploring a substantial area of previously inaccessible private land.

It was during the heady days of discovery in 1987 that the term “Carlin Trend” was coined. The footprint of the known Carlin Trend stretches over 35 miles, from Newmont’s Rain/Emigrant deposits on the south end to Barrick’s Dee/Storm deposits on the north end.

To support increased mining and address the challenges posed by significant distances between deposits, new mills had to be built. Mill No.2 was commissioned in 1985 at Gold Quarry, and Mill No.3 was commissioned in 1988 at Rain. Also in 1988, Mill No.4 was built in the North Area, while Mill No.5 (an expansion of the Mill No.2 complex) was constructed at Gold Quarry. Large leach pads were constructed in each area, as well, to handle the large volume of low-grade material, which by that time was considered ore.

By 1987, Newmont Mining Corp. had grown to become a multinational company producing copper, gold, coal, oil and gas, cement and other commodities. This attracted the attention of corporate raider T. Boone Pickens. Pickens planned to take control of the company and sell off the pieces. He was unsuccessful in his takeover bid, but this event motivated the company to focus mainly on gold. By 1990, Newmont had sold off many of its other commodity businesses, leaving Newmont Gold as its main holding.

At the end of the 1980s, discovery of Deep Post and Deep Star spurred Newmont to begin thinking about developing underground mines. Both of these deposits were significantly higher in grade than deposits nearer the surface and could not be easily mined with an open pit. The 1.0-ounce-per-ton grade drove planning for an underground mine at Deep Star, which initially was to be accessed by two shafts. However, after several years of planning, the project was shelved, due to its high cost.

During this time, deep ore deposits were identified in other areas envisioned as potential underground mines just outside the Carlin and Rain pits. Underground mining began on both deposits in late 1993, and both were producing ore by the following year. Successful startups at Carlin East and Rain prompted Newmont to reevaluate Deep Star and its planned shaft access. Development at Deep Star began in 1994, with the shaft concept being abandoned in favor of two portal-accessed declines that provided entry into Deep Star at considerably less cost.

Underground mining at Gold Quarry began in 2002 at the Chukar mine. Discovered in 1997, Chukar had an initial reserve of 138,000 ounces and an estimated mine life of two years. Chukar is still producing today and has several years of mine life remaining.

As the open pits progressed deeper, especially at Gold Quarry, Newmont recognized the need for a mill that could handle both sulfides and carbon. The Mill No. 6 Refractory Ore Treatment Plant (“Roaster”) was completed in 1994. The Roaster uses high temperatures to burn off the sulfides and carbon, effectively oxidizing the ore, so that cyanide can be used to extract the gold. When completed, Mill No.6/Roaster was one of the world’s largest such plants.

Between 1990 and 2001, Newmont’s gold production from the Carlin Trend exceeded 1.5 million ounces a year, reaching a peak in 2000 of 1.87 million ounces. The gold price, which for many years had lingered in the mid-$300/ounce range, began decreasing in 1999, ultimately reaching a low of $250 an ounce. These low prices persisted until 2003, when the price slowly began to rise. Decreased production followed the decreased gold price, reaching a low of 873,000 ounces in 2004.

Newmont and Barrick Gold Corp. finalized a land swap in 1997 that gave 100 percent of the Rodeo deposit to Barrick and 100 percent of Deep Post and Leeville to Newmont. Deep Post began production from declines in the bottom of Barrick’s Betze pit in 2001. The next year, surface and underground development for the Leeville Deposit began simultaneously, with a decline being driven from the northern end of the existing Carlin East Underground operation and production and ventilation shafts being sunk from above the deposit.

The Leeville Complex, which also includes Turf and Four Corners, is the largest underground mine on the Carlin Trend. A third shaft will be completed in 2015 to provide ventilation for the Turf orebody.

In 2006, Newmont metallurgists once again found a way to squeeze value out of material once considered waste when Mill No.5 was retrofitted with a flotation plant that produces a sulfide concentrate, which can be fed to the Roaster. Making a concentrate that contains mostly gold from low-grade ore is more cost effective than processing whole ore through the Roaster.

As deposits are mined out, new ones have taken their place. New underground mines in the last five years include Exodus and Pete Bajo, both portal-accessed mines. New laybacks continue at Gold Quarry and Genesis, and Newmont’s Emigrant mine, near Rain, began producing in 2012. As for any future ventures that Newmont might undertake on the Carlin Trend, there are many current and former employees and associates of Newmont who believe the best is yet to come.

Looking back on the 50 years that have passed since that first gold pour, we have to marvel at the degree and frequency of changes that have taken place in a relatively short period of time – from how we mine … to the size of the equipment we operate … to the mill processes we use. But even more astounding is the fact that Newmont has been mining here long enough to have experienced all those changes. Longevity is rare in mining, but thanks to many people – our employees, our communities and our industry partners, we have continued to prosper. Our success at Carlin is largely why Newmont has been able to grow in Nevada and elsewhere around the world. We look forward to the next 50 years on the Carlin Trend. — Newmont Mining Corp.

Looking back on the 50 years that have passed since that first gold pour, we have to marvel at the degree and frequency of changes that have taken place in a relatively short period of time – from how we mine … to the size of the equipment we operate … to the mill processes we use. But even more astounding is the fact that Newmont has been mining here long enough to have experienced all those changes. Longevity is rare in mining, but thanks to many people – our employees, our communities and our industry partners, we have continued to prosper. Our success at Carlin is largely why Newmont has been able to grow in Nevada and elsewhere around the world. We look forward to the next 50 years on the Carlin Trend.

-- Newmont Mining Corp.

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