They're a special breed, likened to robots or followers of a religious sect, such is their unflinching dedication.

Life as a top trader at Glencore, the world's leading commodities marketing group, means grueling long hours and intense pressure to strike killer deals, salved by handsome financial rewards and a family-like camaraderie.

Its shrewd traders are arguably the most valuable asset at the secretive Swiss company, which announced on Thursday it was going public.

When the company lists shares next month, stakes held by the roughly 500 partners will be worth an average $120 million based on an expected valuation of $60 billion, though lock-ups will stop the paper multimillionaires from selling up for one to five years.

It's very hard work, very intense. You've got management teams which establish a culture of high performance among the key personnel, and high incentives, said Henri Alexaline, senior credit analyst at BNP Paribas in London.

It is similar to the high-pressure environment at investment banks such as Goldman Sachs, but perhaps even more extreme, he added. It involves a lot more traveling, and their private life takes a back seat.

MOONIES, ANDROIDS?

The driven band of top traders who make it through a rigorous selection process are cut from the same mold, according to several sources who declined to be identified.

They are so tough, the ones who survive. They are so resilient, like androids. There can be all kinds of horrible things going on, and they rarely lose their cool, said one industry source who has friends at the group.

The person said that staff carried laptops and Blackberries while on holiday, logging on to answer 400-500 emails and being on call 24/7.

An outsider who has worked closely with senior Glencore officials said the group's hard-working, up-or-out culture can be ruthless and even cult-like.

There is an element of the Moonies about Glencore, the person added, referring to the term used by critics to describe followers of the Unification Church.

To say they've all drunk from the same Kool-Aid is an understatement, said another outsider who has worked closely with top company officials.

Glencore says it does not hire senior staff from outside, but promotes insiders to maintain a very strong corporate culture.

Many top traders live almost permanently out of suitcases as they move between the group's more than 50 offices in 40 countries, foremost among them in Switzerland, the U.S. East Coast, London, Rotterdam, Beijing, Moscow and Singapore.

A person who has experience working with Glencore said: I generally worked 10-12 hours a day. The assumption is glam parties in the evenings ... but the reality of the daily stresses means I rarely went out in the week.

RUTHLESS BUT CHARMING

Those stresses are in part explained by a culture in which blunders are not tolerated.

If you make a mistake and you've lost them money, then the whole company will ridicule you because they send these multi-chain emails around, the first source said.

They learn to be really, really careful, because the whole company will laugh at you and you'll lose your bonus.

But while the stresses can be severe, there is also a tight bond among the traders that is cultivated by CEO Ivan Glasenberg, who worked his way up over a quarter century from starting as a coal trader in South Africa.

He's a very charismatic guy. I don't think I can recall anybody that hasn't been very taken with him when they meet him. He's very driven, but very approachable and down-to-earth, the second outsider said.

While Glasenberg can have a fiery temper when things go wrong, he also inspires strong loyalty from his traders, who are hired young and expected to make a career at the company.

A group of traders often joins the 54-year-old boss for his daily run.

That kind of bond limits the prospect of a brain drain from the group when it lists in London and Hong Kong next month.

A lot of them are very loyal to Ivan personally. They'll want to be part of the new structure. They are his loyal lieutenants, the first source said.

They don't need the money; they know they'll be worth far more than they can spend in a lifetime. What they want is the buzz of being part of this venture.

(Additional reporting by Jessica Donati; Editing by Will Waterman)

South Africa BNP Paribas