In February 2005, Sean Gilbertson fired off a memo to Viktor Vekselberg, one of Russia's largest industrialists, who owns the world's biggest collection of Fabergé eggs.
     Gilbertson pitched the idea of teaming-up to buy the Fabergé brandname, largely dormant since the collapse of Tsarist Russia in 1917. Vekselberg agreed. But shortly before the deal closed, the terms quickly changed. Vekselberg made a grab for the asset, requesting full control, but Fabergé slipped through his fingers, going instead to Gilbertson's private equity firm.
    “Obviously at this point Mr Vekselberg was extremely unhappy,” Sean says, sitting at a large round table in a dark sushi restaurant in London, shuffling sushi bowls around the table quicker than a magician.
     Sean, 45, is one of the sharpest (and most divisive) individuals in mining finance. He is best known as the son of Brian Gilbertson, a formidable South African who built BHP Billiton, the world's largest mining conglomerate. But Sean's own career has been a succession of brainwaves and innovations, from metal trading to coal contracts, leading to his current position at the top of Gemfields, the world's largest ruby and emerald group, which he has built largely from scratch in the last 10 years.
     The Gilbertsons work closely together, but their antics in the mining markets are invariably

as baffling as they are grand in scale, often leaving investors looking in different directions thanks to convoluted deal structures, spiring ambitions and desk-thumpingly complex legal agreements. So how do the Gilbertsons think? And how do they operate?

     Sean grew up outside Johannesburg, went to government schools and was under no pressure to “go into the mining realm,” he says, despite his father's position in the industry. “I could have become a fine artist if that's what I wanted.”
     But art was the only course that the young Gilbertson failed. He studied mining engineering at Wits University and did a stint in South Africa's underground gold and platinum mines, battling 3am shift starts and grim working conditions. “You certainly don't need a gym membership whilst you're working underground.”
     Sean wanted to get into finance and landed an internship with Deutsche Bank in Frankfurt, on the basis that he arrived speaking German, so he went to the Goethe Institut for languages in Munich for four months, learning how to order beer and pretzels.
     It was 1995 and Deutsche Bank at the time “only had one P.C. per floor”, which bankers had to book for half-hour slots. Sean had the “distinct advantage” of having been given a laptop computer by a coal-trader friend and as a result,

he says, picking salmon eggs out of his sushi bowl, “my level of productivity was actually quite reasonable.”
     He was offered a job in project finance in Deutsche Bank's London office, where he set about wrapping his head around financial modelling and weighty legal contracts, requiring “months and months and months of paperwork and hundreds and hundreds of pages.”
     As Vekselberg and others have too often but too late discovered, the Gilbertsons have mastered the dark art of imperceptible loopholes and seemingly innocuous clauses.
     “It's extremely frustrating when you pick up your first complex contract and you actually don't understand very much of what's being said at all,” Sean says, his face half lit by a spotlight that picks out the bubbles in his glass of water. “But the more you bang your head against the contracts, and spend time with them, the easier they get and the more you learn. That was one of the key skills that fortunately was instilled in me at Deutsche Bank. The ability to pick up a contract and spot most or at least many of the principal pitfalls. Great skill.”
     By 1998, the internet was kicking off and Sean spotted an opportunity to “strike out” on his own. He had spent a few months with a Czech-owned trading firm in Switzerland and had seen that the coal market was inefficient and fragmented...