Chuck squeezed the Ziploc between his fingers as Elaine continued.
“By the time Walsh made it to Ouray, he’d seen thousands of played-out mines. He went way up into the San Juans, to a high mountain cirque called Yankee Boy Basin that was lined with abandoned shafts.
“The Yankee Boy mines had produced marginal amounts of silver, not gold, and they’d gone bust years before. But thanks to all his research, Walsh noticed something different about the mines in the basin. The tailings dumped down the mountainside during the digging of a mine usually are gray—the color of the hard-rock interior of the mountain. But the tailings from the played-out silver mines in Yankee Boy Basin weren’t gray, they were black. And when Walsh picked up a handful of the stuff and worked it between his fingers, he found it had the consistency of—”
She allowed Chuck to fill in the blank: “Coffee grounds.”
Elaine tapped the air with her cigarette in approval. “Geologists were just figuring out back then that gold exists in numerous forms,” she explained. “There’s the pure kind, shiny and yellow, in the form of grains and nuggets. But there are other forms as well, wherein gold is mixed with other minerals and is not readily apparent to the naked eye. One of those hidden forms is gold suspended in an ore known as calaverite, which looks as gray and unremarkable as any worthless mineral. When calaverite containing suspended gold is exposed to oxygen and moisture, however, a chemical reaction takes place. It turns from gray to black, and becomes loose and crumbly.”
The plastic bag weighed down Chuck’s hand.
“In fact,” Elaine went on, “that’s exactly the process by which gold becomes recognizable to the human eye. Over eons, air seeping through fissures into mountains oxidizes gold in its impure form, turning it into a black, slag-like material. The slow leaching action of water over millions of years turns that black slag into pure gold.
“The silver miners above Ouray unwittingly exposed just such a mixture of tellurium ore and gold to oxygen when they dumped the tailings down the mountainsides. The mixture went through the next steps of the process—oxygenation and leaching by rain and snow—in the years after the mines were abandoned. The first discovery of a large deposit of calaverite was in California in 1868. That was several years after the Pikes Peak gold rush petered out. Most prospectors were long gone, but the timing happened to be perfect for Walsh, who was still on the hunt, and still keeping up on the latest findings in the mining world. As soon as he crumbled that first handful of abandoned tailings between his fingers in Yankee Boy Basin, he recognized it for what it was.”
“Gold,” Chuck said.
Elaine pointed at the black material. “It looked just like that.”
Chuck hefted the baggie. “But this never has been exposed to the outdoors.”
She gave him time to figure it out.
“Oh,” he said. “Right. There’s no need for sunshine. Just air. Oxygen.” He closed his eyes, remembering the current of air that flowed constantly into the mouth of the mine, as if drawn by a fan.
“I suspect,” Elaine said, “that the vertical shaft you told me about has helped speed up the process. I’d be willing to bet there’s a fissure in the mountainside somewhere below the horizontal tunnel. Outside air flows into the tunnel and down the shaft and exits out the lower fissure. Essentially, the mine is one big air convector.”
“You think the shaft was gray-walled all the way to its bottom at first?”
“It couldn’t have been dug if the stuff was as loose and crumbly as you say it is now.”
“But something made them turn and dig vertically.”
“They probably were following a small vein of pure gold ore that eventually played out.”
“When, in fact,” Chuck said, “the last of the pure gold died away into calaverite—that is, into gold in its less-refined state.”
“According to what I learned while poking around online this morning, that stuff you’ve got in your hand is probably ten percent gold.”
He held out the bag. “This?”
“Add cyanide and it leaches right out—which is exactly what Walsh did in Yankee Boy Basin. He bought up the old claims for the whole valley, hired the best miners in the area by paying them double what anyone else was paying, and set to work. In its day, Walsh’s Camp Bird Mine was the most productive gold mine on earth, and it stayed that way for years.”
“A mother lode,” Chuck said.
“Made of coffee grounds.”
Elaine smiled, but Chuck did not. He looked down at the black crumbles that had hidden a skull all these years, with a bullet hole straight through from front to back.