Russian diamond giant Alrosa has referred an investigation of a case of substitution of low value synthetic stones in a batch of Alrosa rough diamonds that was sold to a foreign client to the criminal prosecutors and the Russian courts, reports PolishedPrices.

Andrei Polyakov, the company spokesman, told PolishedPrices that a case of substitution had been discovered "recently". Though Polyakov declined to say who is suspected, and how exactly the substitution was carried out, he noted that the evidence will appear in court.

"It's up to the law enforcement services to find who is guilty,” he said.

According to Russian press reports, Alrosa has acknowledged that the switch occurred in a small batch of stones of up to 3 carats in size, and that though the discovery was recent, the switch is believed to have happened between late 2008 and early 2009 during cutting and polishing of the rough diamonds.

Such switches were known to have occurred during the 1990s in the diamond pipeline between Russia and the Armenian cutting plants.

The Alrosa rough had been replaced by stones treated by the high pressure, high heat (HPHT) synthesizing technology at a location outside the direct control of the main company or its diamond polishing affiliate, Alrosa said.

"Such manipulation of its products may damage the reputation of the company and the diamond as such," Alrosa has said in a statement, "so any attempt to mislead the consumers of precious stones, made of our diamonds, will be stopped in the strongest fashion."