Gold (11 page)

“Bill wanted to show me this unusual ore,” Roberts recalled. “My curiosity was piqued, so I went with him.” The manager of the mine they visited, Gold Acres, led Roberts and Vanderburg to the “pay dirt”—the gold-bearing zone. Roberts saw the familiar zone of shearing, where the older ocean rocks had pushed up over the younger limestones at the continental edge. “For anyone who sees this contact zone in the field,” Roberts wrote, “the color contrast between the dark siliceous oceanic rocks and the underlying gray continental shelf carbonate rocks is striking!”

Unlike the narrow shear zone that Roberts had seen in the Willow Creek mine when he had first visited Nevada as a student, the shear zone at Gold Acres was in places more than a hundred feet thick. Here and there throughout the zone were limestone “lenses”—slabs of limestone torn from the continental rock when the oceanic rock had scraped across it. These lenses contained the ore.

To Roberts, this was a thunderous discovery. If the gold was contained within the shear zone, and the shear zone was a regional feature—
the
geological feature of that part of the state—then the gold occurrences were not local accidents, but part of a structure that ran through the whole region.

“When we entered Maggie Creek Canyon,” Roberts wrote, “I saw for the first time the stunning view of upper-plate black chert riding on iron-stained gray limestone on the east side of the canyon. . . . This visit was a profound and moving experience for me as it confirmed that the thrust was of regional extent and might exert a regional control of mineralization.”

By “control,” Roberts meant that the thrust might be the feature that determined where the gold was to be found. In Maggie Creek he saw that zone exposed to view. It was in limestone that the invisible gold was to be found. The limestone was more porous than the older rocks that sat on top. Gold is formed in the mantle, and rises in a hot solution. If the gold had flowed up into the porous limestone at a point in time after the harder, denser older rocks had thrust on top, the older rocks, Roberts thought, might have “capped” the gold, blocking its flow and penning it in the limestone.

Sometimes when gold penetrates rock, it settles into faults and cracks, cooling into solid veins. This type of deposit is called a lode. But in the deposits Roberts envisaged, an acidic gold-bearing solution had flowed into the porous limestone, dissolving the rock and creating pathways for more gold to follow. The picture that formed in Roberts's mind was of a gold-rich layer of limestone capped by harder, less permeable rock. The harder rock had trapped the gold inside the limestone.
“My excitement grew as I visualized potentially rich ore bodies,” Roberts wrote.

Roberts does not say if he discussed his ideas with Vanderburg,
but according to Alan Coope, a geologist who wrote a history of the Carlin exploration, Vanderburg too had been seized by the conviction that more gold awaited discovery. He thought that explorers would find gold in the kind of shale-and-limestone sandwich that Roberts was identifying as the defining character of the region. Roberts saw the bigger picture. He saw past the gold mine to the goldfield. He knew that where gold had been discovered, the upper layer of rock had worn away, leaving a window into the softer rock below. As he saw it, the gold mines of the region were not located on separate areas of gold-rich ground, but on the same vast zone, one that had been tapped, you could say, by accident. Miners had blundered onto deposits through windows opened by erosion, without understanding the larger structural picture.

Roberts's mission was to map the structures of Eureka County. He led an idyllic life, camped with his family in a trailer on the Dean Ranch in Crescent Valley. His sons explored nearby ghost towns while Roberts and his assistants traced the thrust zone through the hills. Increasingly convinced that the thrust was a main control of regional gold deposits, and looking for a pattern to confirm this conjecture, Roberts made a rough map that plotted the ore deposits and the windows on the thrust. A clear line jumped out. It trended northwest through Eureka County.
In 1960 Roberts put his thoughts into a two-and-a-half-page paper, “Alinement of Mining Districts in North-Central Nevada.” He asserted his belief that windows in the cap of older rock gave access to zones that had been “penetrated by conduits along which igneous rocks and related ore-bearing fluids rose. The zones probably penetrate to great depths within the crust. . . . In prospecting within the windows, a special effort should be made to explore the lower units.” In other words: Dig the windows, and dig deep.

Roberts perceived a condition that he could not see. Like an astronomer deducing the existence of a body outside the range of observation, he created a hypothesis out of what he knew. He could see that microscopic gold was present in pieces of limestone. He could see that the limestone was part of a regional structure. From these observables he built the mental image of a goldfield of invisible particles trapped beneath the older shale. The only way to test that theory was to drill the exposed limestone in the windows. As a government geologist, it wasn't Roberts's job to drill, but to convince someone else to drill.

The man Roberts found was an intrepid loner—like Roberts, a man who loved the silence of the mountains. His origins were very different from Roberts's: born into one of America's grandest families, he had left behind a privileged existence at the top of the social world to pursue a solitary life. For years he and Roberts, unknown to each other, had explored the same mountains at the same time, in search of the same gold.

Roberts's paper on the windows appeared in 1960. The next year he addressed a meeting of geologists at a hotel in Ely, not far from Eureka. Most of those present were oil geologists, not much interested in Roberts. His talk came at the end of the day. As soon as it was over, the room emptied out in the direction of the bar.
One man stayed behind.

John Livermore was a lanky, six-foot-five-inch gold geologist who had read Roberts's paper. It had stunned him. On and off through the 1950s, he had explored the mountains searching for exactly the kind of gold deposit Roberts had described, and in that short paper on the alignment of mines, he read where to look.

J
OHN
S
EALY
L
IVERMORE GREW UP
in San Francisco, in a redwood mansion on San Francisco's Russian Hill. His name and those of his brothers are preserved in a stained-glass window above the south transept of the city's Grace Cathedral. Mount Livermore, on Angel Island in San Francisco Bay, was named for Livermore's mother, Caroline, a conservationist who helped preserve it. The family spent summers at Montesol, the 7,000-acre ranch in the hills north of Napa that the Livermores had owned since 1880. Livermore admitted to a “pretty perfect childhood,” but the life it pointed to, of social prominence, did not attract him. With a geology degree from Stanford University, he took up the nomad's calling and became a prospector.

Livermore's search for invisible gold began in 1949 at the Standard mine, a gold mine north of Lovelock, Nevada. It had closed during World War II. The owners wanted to start it up again, but needed to find a new supply of ore. The mine had been established on a lode deposit. If the host rock was fractured, Livermore thought, or if there had been repeated gold intrusions, particles of gold might have been forced outward into the surrounding rock in a kind of low-grade mist of gold. Livermore found plenty of such low-grade rock, but not the richer, higher-grading source rock that should also have been there.

“We did some churn drilling,” Livermore later recalled, referring to the use of wide-diameter drills, “and found some ore.” But the ore was not high-grade, and “the mine was really sort of doomed already. It was a very, very low-grade mine, and they were not making much money. To develop this ore that we were finding would have involved quite a lot of stripping [removing non-ore-bearing rock], and they just weren't generating enough money to continue.” In a few months the mine shut down and Livermore was out of work. He tried to find another job, and when he couldn't, did what he liked best—trekked out into the land and looked at rocks.

For two years he prospected alone in the Nevada mountains. He had been hooked on the idea of deposits of undiscovered gold in that part of the state since reading a paper by William Vanderburg, the engineer who had taken Roberts to Gold Acres. As Livermore searched, he wondered if the low-grade ore of the Standard mine might represent a different, unidentified kind of gold deposit, and not a low-grade example of an ordinary lode deposit. To fit the accepted model of a lode, the gold should have occurred in hard, volcanic rocks. Instead, it was in softer rocks, such as limestone. Moreover, the grains were so tiny as to be invisible. Only an assay could detect their presence. But if this invisible gold was a new kind of deposit, what accounted for it? Livermore needed to imagine some new process that would enable such mineralization to take place, a theory to explain the presence of the gold. He set about to build one.

In Livermore's conjecture, the gold rose from the mantle into the crust in the same kind of solution that created normal lode deposits. But instead of the gold precipitating out into the wall rocks of the channel and concentrating there, it flowed into relatively soft and porous limestone, dissolving some of the rock to create yet more spaces to flow into. In north-central Nevada the rocks were already cracked and broken from seismic action, providing more routes into the limestone for the hot, acidic gold-bearing solutions that Livermore conceived. He was imagining what Roberts later would hypothesize.

In 1952 Livermore took a job with Newmont Mining Corporation. For the next six years he worked on projects in South America, Morocco, and Turkey. In 1958, recovering from an illness, he took a desk job at the company's headquarters, then in New York. He found it tedious, and his thoughts returned to Nevada. In 1960, on assignment at a base metals mine in Eureka, he persuaded his boss to give him time to look for gold.

Livermore has described the warring emotions that accompanied
him through the empty landscape. “I really and truly believed I would find gold.” Yet this feeling was tempered by doubt. As a geologist he knew that the chances of discovering an economic gold deposit were slim. “Gold will always surprise you—more than any other mineral, I think,” he told
The New Yorker
's John Seabrook almost thirty years later. “You can't predict it. You get some decent gold values in a sample and you sort of think to yourself, Aha, I'm onto you now, I've got your secret this time. Then it turns out you don't—the gold was just playing with you.”

Livermore persisted anyway, consoled by his affection for the land, even as it bruised his hopes.
“I get lonely sometimes, too,” he admitted, “living in those motel rooms, spending all day by myself. I ask myself why I'm prospecting. It's not to be rich. It's nice to have the money, but, honestly, that's not why I do this. I don't know. It's something about—about the finding. If I could just find that gold, then everything would be OK. It's this endless puzzle, and sometimes—I don't know—it seems more important than it really is.”

It wasn't even worth that much—$35 an ounce. The only large gold mine in the United States at the time was the Homestake mine in Lead, South Dakota—at 8,000 feet, the deepest mine in America when it closed in 2002. Homestake produced 40 million ounces in its lifetime, and a belief had taken root among miners that there were no great deposits left to be found in the United States. And if there were, they would not be found in north-central Nevada, scraped and sifted for a hundred years. Yet that is where Livermore found it, not so much a deposit as a sea of gold.

When he saw Roberts's paper, with its simple plot of existing mines, mines already harvesting gold through the windows,
“That really got me interested,” Livermore said, “because now I had a model to follow to try to find some of these deposits. I thought there was a
good chance they existed. Maybe the old-timers would have missed them because of this fine gold, but now with his theory, maybe this was a way to look for these deposits. Maybe just by carefully mapping and prospecting this Roberts Mountains thrust, we could find more of these deposits.”

With nothing fancier than hammers and canvas sample bags, Livermore and an assistant set out along the thrust. They sent their samples to Harry Treweek, an assayer who lived with his wife in a secluded cabin in Crescent Valley. Assayers heat ore with chemicals called fluxes. The fluxes combine with everything but the gold, which settles out of the mixture, where it can be weighed. Its weight is expressed as fraction of the tested ore, in ounces or grams per ton—the grade.

“We had confidence in him,” Livermore said of the assayer he used, “because these samples we were taking were often very low-grade samples, and we wanted to be sure that what he was reporting were true values, and not just spurious values.”

Livermore's discovery can look simple: Roberts tells him where to look and the rest is easy. But the windows that provided openings into the prospective limestone were scattered over 5,000 square miles. In Livermore's estimate, he mapped a mile a day. For two men based at a motel in Carlin, armed with nothing but rock hammers and a map, the exploration was a daunting task.
Then Livermore visited Harry Bishop, manager of the Gold Acres mine, where Roberts had first examined the ore that contained invisible gold. Livermore asked Bishop where he would look himself, if he had the whole Roberts Mountains thrust to search. Bishop told them he would start just north of Carlin, where explorers had found gold at the Blue Star turquoise mine.

In June of 1961 Livermore started his examination of the Blue
Star mine. He mapped and sampled the deposit for three weeks, sending rock to Harry Treweek in Crescent Valley. When his assessment was complete, Livermore had outlined 500,000 tons of ore. He recommended the property to Newmont. When Newmont couldn't close a deal with the owners, Livermore moved to another target, and it wasn't far away.