Gold

by Matthew Hart

  The first discovery on record came in 1849, when a party of Mormons heading for the California gold rush camped at Carson River to wait for the snow to melt from the mountain passes. They panned the streams, and recovered gold. They moved on westward in the spring, but Gold Canyon, as the site became known, attracted other placer miners. By 1857 successive waves of prospectors had pushed upstream, always finding gold. A second discovery, to the north in Six-Mile Canyon, brought more searchers into the foothills. Finally in 1859 they hit on where the gold was coming from—a rich gold-and-silver deposit near Virginia City, the famous Comstock Lode. Soon the passes were swarming with men leaving California for the new bonanza. Prospectors poured into the state and fanned out through the mountains. They found placer gold in the streams near Battle Mountain and Winnemucca. In the clefts and watercourses of the hills that Roberts was exploring, you can still see sluices and stone dams and the collapsed entrances of adits. The gold mine at Willow Creek that Ralph Roberts wanted to explore dated from that teeming gold camp.

  The mine belonged to Wallace Calder, a Winnemucca dentist. Calder told Roberts he’d recovered large nuggets from a fault zone in the mine, and Roberts arranged a visit. Calder showed him where the nuggets came from. Examining the rocks close up, Roberts saw that they were oceanic rocks, much older than the rocks they sat on. In the normal course of geological formation, new rock comes up from the mantle in molten form, and is deposited on top of older rock. Here, those relative positions were reversed. To explain what had happened, Roberts hypothesized a thick shelf of older oceanic rocks thrusting up onto the younger limestone at what had been the western edge of the continent. By the end of the summer, although he was years away from forming a theory about the region’s gold, two pieces of that theory were now in place in his mind: first, older ocean rocks had been pushed up onto younger rocks at the ancient seashore; and second, that gold occurred within and below the zone where that thrust occurred.

  Today, geologists recognize the thrust as the product of a tectonic collision, where two of the earth’s crustal plates mashed against each other in the geologic past. But the plate theory did not emerge until the 1950s. In 1939, when Roberts began his explorations, the most important guide to the regional geology was a nineteenth-century report called the Fortieth Parallel Survey. Commissioned by the secretary of war and published in 1877 and 1878, the survey was an eight-volume natural history of parts of Nevada, Idaho, and Wyoming. The writers described huge tables of Triassic rock and mountainsides alive with “minute brilliant-black crystals of tourmaline” and “small brown iron garnets, not much bigger than a pinhead.” Field geologists have an unquenchable appetite for such details. Diamond hunters obsess over garnets, which can point the way to diamond pipes. Roberts’s interest was the larger structures of the region, and one day the camp cook dropped him off at an abandoned silver mine. He struck out along the Antler range in his happiest state—alone.

  Earlier geologists had identified the range that Roberts followed as 300-million-year-old limestone. Limestone is composed of the skeletal remains of tiny animals from the shallow seas, in this case, seas that had once lapped at the continental shore in present-day Nevada. The limestone takes its pale color from the minute skeletons that make it up. When the ocean plate and continental plate collided, according to Dean Heitt, a Newmont Mining Corporation geologist who has written a history of the Carlin Trend, “the darker, older rocks from the deep ocean, such as cherts and shales, pushed up onto the younger, light-gray limestone, covering it.” When Roberts set out to understand the regional geology, finding a theory to explain how the older rocks had ended up on top of the younger rocks was part of the exercise. “As I approached the western margin of the range,” he wrote, the “limestone pinched out,” and older rocks appeared on the ridge he was traversing. “I could see a few fragments of limestone on the ridge, but the massive unit that I had followed earlier was gone.”

  Roberts did not know it, but he had crossed what he would come to call a “window”—a place where the older, darker rock had worn away and revealed the younger limestone underneath. At that break in the older rocks that had been thrust up from the deep ocean, Roberts located an opening into the richest gold-bearing rocks in America. He was “seeing through” the cap of older rock that concealed the limestone. In the Willow Creek mine he had already seen a hint of what he would later understand more fully—that gold lay in the limestone layer below the older rocks. He had come across a place where an explorer could reach in and rummage for gold without having to penetrate the barrier of older, harder rock. That Roberts did not see this shortcut right away is because he hadn’t started looking for it.

  Roberts’s work was interrupted by World War II. He joined the wartime search for strategic minerals, and was posted to Central America. He did not return to Nevada until 1954, when he took over a unit mapping the geology of Eureka County. That appointment set him on the path to his discovery.

  In Roberts’s autobiography, written when he was ninety-one, an unselfconscious brio lightens the pages. The reader cannot help but feel that here was Fortune’s darling, a man delighted by the life he found in front of him.

  RALPH JACKSON ROBERTS WAS BORN in 1911 in Rosalia, Washington. Both parents came from nearby wheat farming families. As Roberts tells it, his father got tired of slinging 120-pound sacks of grain, and left the farm to become a druggist. He tired of that too, when the long hours of keeping a small-town pharmacy wore him down, and he took to selling Edison record players. Finally he bought a candy store in Omak, eastern Washington, a town in the Okanogan Valley. While he made “incomparable peanut brittle, nougats, pinoche, divinity, caramels, butterscotch, taffy, and fudge,” his son took over the soda fountain.

  For a future geologist, Roberts was lucky with his teachers. One was a first-rate chemist and another ran a thulite mine. Thulite—sometimes called rosaline for its blazing pink color—is a crystalline mineral cut into slabs for use as decorative facing. Roberts helped to quarry it. He also made forays into the surrounding hills to look for gold with “Dad” Hayes, a handyman who had lost the fortune he’d panned from Alaskan gold creeks.

  Roberts picked up mining lore from his family too. One of his mother’s uncles had a silver mine in Colorado, and uncles and cousins on his father’s side had filled him with tales of their mining exploits. Even the Roberts Mountains of north-central Nevada, his exploration ground, had been named for a distant relation.

  Roberts’s account hurtles along. Dancing lessons in wartime Washington occupy the same chapter as the development of the cordilleran geosyncline 380 million years ago. In the same six pages he meets his future wife, a classmate’s girlfriend. “Our eyes met and held for a long moment. She was wearing Warren’s ring, but her greeting to him seemed restrained. . . . I do not remember much about that visit, except that I was drawn to Arleda. Since she was Warren’s girl, I tried not to let my feelings show, but I suspect that she knew I found her attractive, and I sensed that she was interested in me.”

  He sensed right. Two years later Arleda wrote him out of the blue to say that she had returned her engagement ring and would like to see Roberts again. He took her to dinner and proposed before they reached dessert. They had a long, eventful, happy marriage. A photograph from 1954 shows her smiling in the sun with their three children in front of the forty-two-foot trailer where they lived when Roberts set out to map the geology of Eureka County, and made his great discovery.

  Roberts mapped northward through the Cortez, Shoshone, and Tuscarora ranges. He saw that the feature called the Roberts Mountains thrust presented a continuous geological relationship—deep-ocean rocks pushed up over shallow-water limestone. He believed that the thrust was a regional feature, not a local one. He had uncovered the basic geology of what is now called the Carlin Trend. He had taken a giant step toward unmasking the deposit, although another crucial step remained: realizing it was there. Certainly there was historic evidence of gold from early placer mi
ning, and the Willow Creek mine had yielded nuggets. But such occurrences don’t by themselves suggest a single massive source. Yet as Roberts was coming to understand the geology of the thrust, another man was scrutinizing local gold production, and realizing that some of the gold was coming from ore unlike any other he had seen. One characteristic distinguished it. The gold was invisible.

  William Vanderburg, an engineer with the U.S. Bureau of Mines, had been making reconnaissance surveys of Nevada since the 1930s. He had regularly visited the mines and described deposits. He had been struck by the observation that at some gold mines the particles were so fine they could not be recovered by panning. The mines were recovering gold, but when Vanderburg panned a sample of the ore he got nothing. It was “impossible to distinguish between ore and waste except by assay,” he wrote, “and gold is present in such a state that it is impossible to obtain a single color [visible gold] by panning.” At one point there must have been visible gold, or there would have been no mining. At some point, then, the miners had used up that original reserve of ore, but found that the recovery mill was still producing gold even when they moved beyond the original deposit and started feeding in rock that did not have visible gold. They kept getting gold, so they kept mining.

  “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.

  JOHN SEALY LIVERMORE 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.