The Geneva prosecutor's office confirmed on Tuesday that it had opened an investigation into the alleged disappearance of a 50.66-carat pink diamond being held by storage and transport firm Malca-Amit.
"Malca-Amit denies any involvement in the alleged disappearance of the diamond and is fully cooperating with authorities," the company's Geneva manager Francisco Bautista told AFP, blaming the South African-Guinean diamond trader who had filed the suit.
Sylla Moussa, head of the Johannesburg-based Sylla Diamond International, told AFP he had filed a complaint against the company last September after the gem vanished.
"They are a bunch of thieves," Moussa told AFP, insisting he would not leave Geneva until he had found his jewel.
"I just want my diamond back," he said in a telephone interview.
Moussa said he placed the large, rectangular diamond in storage with Malca-Amit in 2007 as he waited to sell it for the best possible price.
But when he wanted to see his gem last August, he was told it had been transferred to a South African businessman, Moti Abbas, who Moussa claims is the mastermind behind the "crime".
'Strangely similar scheme'
That transfer, he lamented, happened despite a storage agreement he signed with Malca-Amit on August 16 2007, stipulating he was the only owner of the stone.
Malca-Amit however tells a very different story, alleging that Moussa had given the diamond to Abbas in 2008 in payment for a debt, and so it was no longer stored under his name.
"Moussa came to Malca-Amit in Geneva and personally delivered the diamond to Abbas, in the presence of witnesses," the firm said in a statement, adding that Abbas had returned the gem to storage under his own name.
"Needless to say, since Moussa had not been the party storing the diamond since 2008, he was unauthorized to issue any instructions concerning it," the company said.
Bautista, who said Malca-Amit no longer had the diamond, also pointed to reports in South African media alleging that Moussa had been charged with defrauding a bank, as well as with fraud, theft and money laundering.
In particular, he noted reports of "a case which appears to be strangely similar to the present one," in which the dealer had wrongfully accused several South African police officers of stealing his gems.
Moussa hit back, accusing the company of "defamation" and saying he had "nothing to hide".
"They are the ones under investigation, but instead of answering questions, they are attacking me," he said.
"I have never been convicted of any crime whatsoever," Moussa said.
He said he was confident that the Geneva probe would prove him right.
The two sides also disagree on the price, with Moussa maintaining the diamond was recently valued at around $75 million, although he is requesting "only" $50 million in compensation for the lost gem.
Malca-Amit insists the diamond was valued at just $15 million when it was placed in storage, and Bautista said "qualified diamond experts" had estimated it was worth $5 million "at best".