It’s early January, and Eira Thomas is steering her 2003 Porsche Carrera 4 through Vancouver’s Stanley Park, which looks as if it’s been ravaged by a hurricane. The city is being raked by its 14th storm since November, and has lost about 10,000 trees to high winds. A caller on Thomas’ cell phone warns her that a causeway leading out of the city will soon close. She snaps the phone shut and drops the Porsche into third gear. She’s soon flying over the bridge.

Thomas has never been one to be put off by inclement weather. The daughter of a Welsh mining engineer who toted her along in the field as a child, she grew up with mining in her blood and mud on her boots. And in 1994, 180 miles northeast of Yellowknife in Canada’s remote Northwest Territories—a latitudinal notch from the Arctic Circle—she led the field team that discovered a multibillion-dollar diamond deposit known as Diavik.

In the 13 years since, Thomas has evolved from a poster girl for Canadian diamond exploration into a boardroom brawler, one who recently triumphed in a three-way, $120 million merger that was one part friendly, one part hostile. Tall and fit, with alabaster skin and flowing red hair, Eira Thomas has become, in the eyes of many, the ideal mining company C.E.O.—an agile mix of scientist, strategic thinker, and promoter.

Her company, Stornoway Diamond, is still small in comparison with industry giants like De Beers, BHP Billiton, and Rio Tinto. But it is well positioned to become a big-league player at a time of consolidation in the industry. Thomas’ goal: to reprise her monumental diamond strike by combing an astonishing 22 million acres under lease. Thomas is out to prove that she is not just the luckiest woman in the world but that she remains a diamond explorer to bet on.

Since the December 2006 release of Blood Diamond, the latest Hollywood blockbuster with a social conscience, consumers have been wringing their hands over whether their diamond purchases are financing rebel armies in Sierra Leone. The Leonardo DiCaprio vehicle tackles important issues, but many in the industry say that so-called blood, or conflict, diamonds are an old story. And in a sense, they are. Though working conditions in the continent’s diamond fields remain well below first-world standards, there are no active conflicts being funded by the illicit sale of diamonds in Africa today.

The industry would prefer to concentrate on its feel-good story of the decade: Canada, which went from being a nonfactor to the third-largest supplier of rough diamonds in 2003, contributing some 13 percent of a worldwide total of $9.24 billion. In 2006, according to WWW International Diamond Consultants Ltd., Canada produced $1.2 billion worth of rough diamonds; its ranking, however, had slipped to fifth. 

Until the 1990s, North America was jokingly referred to as a good place to sell diamonds but a bad place to find them. So wrote Matthew Hart in Diamond: A Journey to the Heart of an Obsession. All that changed when explorers Charles Fipke and Stewart Blusson sent a shock wave through the diamond world with the 1991 announcement of a diamond find at Point Lake, north of Lac de Gras, in Canada’s Northwest Territories. Further discoveries by Fipke would ultimately turn into the Ekati diamond mine, Canada’s first, and would make Fipke and Blusson very, very rich. Canadian Business magazine pegs Fipke’s net worth at $445 million and Blusson’s at $573 million. The finds would also set off a staking frenzy not seen since the Klondike gold rush in the Yukon Territory.

Enter Eira’s father, Grenville Thomas, a colorful mining engineer with a thick Welsh brogue. Grenville emigrated to Canada in 1964 and found work at a nickel mine in Sudbury, Ontario. He soon found his way to Yellowknife, and was well known among Canadian gold miners by the 1990s. After Fipke’s diamond discovery, Grenville quickly began staking ground east and southeast of Fipke’s dig for his own company, Aber Resources. Grenville admits that he relied on a strategy he jokingly insists is a bona fide mining term: closeology. In a staking rush, he explains, you look for ground as close to the discovery as you can get. “Forget all the other ‘ologies’—geology, biology, and the like,” he says. “Mines tend to be close together. That’s closeology.”

After burning through the cash in its treasury, Aber had to bring in a partner, Rio Tinto. Rio gave Aber $10 million in exchange for 60 percent of the project. In May of 1992, Eira, who had recently graduated from college with a degree in geology, managed to get herself assigned to Aber’s field team. By 1994, the staking rush had pulled team members in so many different directions that Eira was effectively made senior field geologist by default.

In May of that year, Thomas and consulting geologist Robin Hopkins, acting on a hunch, decided to drill underwater, off an island in Lac de Gras. The drill crew wasn’t happy about it, but Eira insisted. When Thomas and Hopkins inspected the core sample, what they found took their breath away: a two-carat diamond embedded inside. Thomas slept with the core sample under her pillow and flew to Vancouver the next day. After she presented the sample to her father, all he could muster was a single word: “No!” Her response was just as concise: “Yes!”

Eira Thomas, leading the Aber field team, had discovered what was then the highest-grade diamond mine in the world, estimated to contain more than 100 million carats, worth roughly $9 billion. The stones are of such high quality that, in 1999, Tiffany & Co. cut a deal with Aber to provide the high-end retailer with some $50 million in diamonds annually through 2013. Thomas’ find was so lucrative that Aber recently spent about $242 million to purchase the world-renowned jewelry house Harry Winston.

The Canadian discoveries did something else that was extraordinary. They effectively broke the back of the De Beers cartel, as demonstrated in July 2000, when the famously secretive South African company announced it would stop its efforts to control the world’s diamond supply. In a glorious understatement, chairman Nicky Oppenheimer later explained the decision: “As new sources of supply opened up—particularly in Canada—it became evident that that role could not be sustained.”

The Canadian media glommed on to the Eira-as-heroine story. But critics contend that Thomas has gotten an inordinate amount of play out of the Diavik diamond strike and that she’s been taking too much credit. Thomas bats this aside as sour grapes. “When I tell the story, it’s always a team effort,” she says. Still, she acknowledges that some people are unhappy with the way the credit has been distributed.

At some point, however, her overexposure seems to have contributed to what would become a full-scale rift with the Aber management team. Longtime family friend Bob Gannicott, now chairman and C.E.O. of Aber, refused to make himself available for this story. Those familiar with the interpersonal dynamics say the reason is obvious—because he’s sick of talking about Eira Thomas. Says one: “The people at Aber fucking hate it when you mention Eira.”

Both Thomases would step down from Aber’s board in 2006. It’s a sore spot, something Grenville will characterize only as “a falling out.” Matt Manson, formerly of Aber and now president of Stornoway, is less generous. “Bob Gannicott goes to the Oscars now,” he says, referring to Aber’s purchase of Harry Winston, “while we still think there are more diamonds to be found.”

It was to find those diamonds that Eira Thomas founded Stornoway in 2002. Her new partner and chairman is Catherine McLeod-Seltzer, another prominent woman in the exploration community. In 1993, McLeod-Seltzer cofounded Arequipa Resources Ltd., which made a major gold discovery in Peru and was later bought by Barrick Gold for $1.1 billion in 1996.

When I ask McLeod-Seltzer whether logic would suggest that the very last people one should back in an exploration company are those that have already had once-in-a-lifetime discoveries, she laughs. “I’d rather back lucky people than unlucky ones,” she says.

Thomas explains that she and McLeod-Seltzer are simpatico because having explorer fathers inured them to the highs and lows that come with the job. They recall with humor the vicissitudes of growing up in a mining household: One day you come home from school and there’s a pool going in; “the next day, you come home, all the lights are off, there’s no heat, and your dad is saying, ‘Put a sweater on! Why do you need heat anyway?’ It’s the roller-coaster ride of this industry.”

The Stornoway team has already had exploration success, including the 2002 discovery of several promising prospects in Canada’s eastern Arctic territory of Nunavut. The result was the second staking rush in a decade, with Thomas leading the way rather than merely following. But the company has had nothing approaching a repeat of Diavik. Thomas is undaunted. “Ultimately, we’ll find another Diavik,” she says. “Given enough time and money, I know we will do it again. It’s not even an ‘if.’ It’s a matter of when.”

Eira Thomas was born in Calgary, Alberta, on November 20, 1968, to Grenville and his Canadian wife, Gail. The name Eira is Welsh for “snow,” reflecting the weather that day. The eldest of four children, Thomas spent her early years moving from one promising exploration venue to the next. The family was living in Yellowknife when she was born, but moved to Calgary, Wales, and Vancouver before Thomas was a teenager.

In other words, she comes by her interest in geology honestly. Her father remains one of the most revered explorers in Canada. “Gren has incredible goodwill in the north,” says Bob Bishop, editor of the Gold Mining Stock Report. “In Yellowknife, you’d think you’re walking around with God.” After graduating from high school with a tentative plan to head to the University of British Columbia the following fall, Thomas went up to Yellowknife for the summer. She very nearly stayed. “I had such a great time that I didn’t feel compelled to continue my education at that point,” she says.

Her mother was aghast. “She saw it as a bad omen—I was going to stay up north and never finish my education. And this would have been a total disaster,” says Thomas. Mother prevailed, winning her over with the idea that perhaps she’d be happier 2,750 miles away, at the University of Toronto. After starting out as a biology major, Thomas switched to geology in her second year. “But I didn’t know at the time it would be my life’s destiny,” she says.

By all accounts, Thomas has managed to keep a modicum of balance in her life. One of her closest friends, Mat Wilcox, says Thomas surprises her constantly. “We were up north, and Eira decides she’s going to adopt these sled dogs,” Wilcox says. “We didn’t have leashes, and they had diarrhea all over the plane, but she didn’t care.” Although she ended up selling the sled dogs, Thomas now has two of her own, both of them a mix of husky, wolf, and hound, with bright blue eyes. Thomas named them Melville and Hudson, after Nunavut’s Melville Peninsula and Hudson Bay.

Thomas’ previous pet, a sled dog named Thor, was briefly as famous as his owner. In the early days at Lac de Gras, Thor was spooked by gunfire and took off running, eventually making it all the way to Fipke’s camp some 60 miles away. Suspecting a ruse by Aber, Fipke’s people wouldn’t let Thomas pick him up at their camp, forcing her to fly all the way back to Yellowknife to retrieve him. The whole episode earned Thor the sobriquet Spy Dog of the North.

At the end of each day, Thomas retreats to a two-story hideaway sandwiched between mountains and water in the hills outside West Vancouver. Decorated with Inuit art, the house is sparsely but elegantly furnished. It has a jaw-dropping view across Howe Sound to Bowen Island, but its relative isolation from town would probably be unacceptable for most unmarried people.

But this is a woman who finds inspiration in the endless tundra of the north, who vacations from a life spent working in the Arctic by hiking up to one of the base stations at Everest—a woman who likes Sun Valley, Idaho, because of its remoteness and who recently bought a plot of land there after coming across it while vacationing with her dogs. (That trip, by the way, included a 20-mile ski-joring race—wearing skis and being pulled by her dogs—that she’d decided to train for on a whim.)

Thomas admits that she loves diamonds just as much as the next girl. She laughingly recounts the time that Harry Winston vice chairman Peter Schneirla allowed her and McLeod-Seltzer to try on all of the jewelry in the New York store. “Peter is an honorary member of our Tiara Club, which he’s quite happy about,” Thomas says. If owning actual Harry Winston jewelry is required for entry, Thomas has that covered: Her father recently bought her earrings and a watch.

Mind you, Thomas hadn’t done much in the past year—beyond working nonstop to pull off the $120 million, three-way merger announced last July and completed in March. The deal united Stornoway and two rivals, Ashton Mining and Contact Diamond. The goal was to create a mid-tier diamond company that can finance its own exploration. That would allow investors to bet on the next diamond discovery without the risk of their stakes being severely diluted should the company have to sell stock to raise cash. If Stornaway is successful, the returns could be phenomenal. Aber is a case in point: It traded for $0.30 a share at the beginning of 1991. Today, it trades for $36, a 120-fold return. (Stornoway shares have generally bounced between $0.15 and $2.15, depending on the latest dispatches from the exploration front.)

The deal at first seemed a fait accompli, as Thomas’ old friends at Rio Tinto had sold its 52 percent stake in Ashton to Stornoway. But the reaction from some quarters was angry and pointed. In a September report, industry analyst John Kaiser called the takeover bid a “clumsy, hubris-fueled exercise in power-tripping.” In January, he was not contrite. “Eira refuses to admit that her exploration efforts have failed,” he said. “Basically, she took Ashton away from [its minority shareholders] to save her own company from dying.”

Mention Kaiser to Thomas, and she almost chokes on her tongue. “I would have said that we were friends,” she said in January, “but it’s pretty hard to say that now.” (More recently, Kaiser seems to be coming around; perhaps they can bury the hatchet.) Both she and Manson, Stornoway’s president, dismiss the idea that they’re stealing Ashton’s crown jewels to make up for their own failures. “That’s just silly,” Thomas says, pointing out that even the best-case scenario for Ashton’s most promising prospective mine, in Quebec, is estimated at 21 million carats at most, a fifth of the amount found in Diavik. Not exactly the kind of project she’d look for if she were mounting a diamond heist.

How does Manson feel about walking in the inevitable shadow of Thomas? “I’ve done a lot of work in diamonds,” he says. “But people don’t remember me. She’s got that something-ness that some people have. It’s called celebrity. I’ve got no problem with it at all.”

Over dinner with Thomas, Grenville, and Manson at the Red Lion—a pub Grenville built when his own local was torn down—the conversation ranges from George MacDonald’s Flashman novels (adventure stories, naturally) to the travails of another Canadian corporate icon, Conrad Black.

Between the second and third bottles of wine, Manson suggests a new way of looking at the diamond business. “Diamonds are more like Gucci handbags than copper,” he says, noting that exchanges do not track diamond prices the way they do copper prices. But, he adds, diamonds are also “the only nondiscretionary luxury product. Most women are given a diamond in their lifetime. Most women are not given a Gucci handbag.”

Eira Thomas could buy a Gucci handbag for herself if she wanted one. But she’s also got something money can’t buy: the respect of De Beers. Says Richard Molyneux, the former president and C.E.O. of De Beers Canada: “I would put her team in the top 10 junior companies involved in diamonds in Canada. If something came up, De Beers would be very happy to work with her.”

Industry guru Martin Rapaport—whose Diamonds.net is a trusted source of diamond prices and market information for the industry—explains why Thomas, a woman who could just as well be modeling diamonds as exploring for them, has managed to fit into what is otherwise almost exclusively a man’s industry. “She’s a woman with boots,” he says. “She’s not just a woman sitting in the boardroom.” She’ll probably put those boots back on this year and return to the field. Because, while she says she’s enjoyed the learning experience that came from pulling off a merger, it’s quite clear that corporate maneuverings are not as close to her heart as stomping around in subzero temperatures in the Arctic.

In the meantime, Thomas plans to unpack the boxes still unopened from a move two years ago. It was in the half-unpacked mess that she lost a pair of earrings set with two-carat diamonds from the Diavik mine. She’s pretty sure her dog Melville ate them. (“He likes shiny things,” she says.) She’s philosophical about the loss, even though the earrings held great meaning for her. “Like my dad says, you can’t get caught up in material things. Perhaps it’s a sign to focus on what’s next.” Like figuring out how to tease lightning into striking twice.