Kim Kardashian robbery: How do you sell high-profile diamonds?

A stone worth several million euros is likely to have been laser marked, said Neil Duttson, a top diamond trader based in Hatton Garden, London.

The laser makes an invisible mark on the girdle - the side - of the stone, but it isn't foolproof. "The mark can be polished off by someone who knows what they're doing," said Mr Duttson.

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A $4m stone would still bring unwanted attention on the market though, so it's likely it would be cut into smaller stones. That would lower the overall value of the original, but it would also make new, untraceable diamonds.

"Once it's been recut that's it, the pieces are invisible, gone for life," said Mr Duttson. "They probably already have someone removing the stones and going to work as we speak."

The stone would probably go first to a known handler, lined up in advance, said Lee Henderson, an intelligence officer for diamond security company SaferGems. Unless it was stolen specifically to order, most dealers "wouldn't go near the original stone with a barge pole," he said.

French police suspect specific stones may have been targeted after being seen on social media. Mrs Kardashian West posted a picture on Twitter just three days before the robbery showing off a large diamond, reportedly a gift from her husband, the rapper Kanye West.

"Clearly when you have a star like Kim Kardashian who has, I think, more than 48 million followers on Twitter ... I think this could have happened abroad just as easily as in Paris," Johanna Primevert, chief spokeswoman for the Paris police department, told the Associated Press news agency.

"It was really the celebrity who was targeted, with possessions that had been seen and noticed via social media, and it was these goods that the attackers targeted."

The gold settings around the stones would probably be discarded, said Mr Duttson. Melting down that amount of gold is unlikely to be worth the trouble, and trying to sell them in a pawn shop would be a rookie mistake.

It would be "horrendously difficult" for the police to recover the stone, he added. "Unless you're really stupid and you buried it in your back garden then had a big argument with your wife about it in front of the neighbours, it probably won't ever be found."