A Sri Lankan gem trader who owns the world’s largest blue star sapphire has decided to sell the dazzling stone, with a dizzying asking price of US$300 million, AFP said.

The rare, egg-shaped stone weighs 1,404.49 carats and has been authenticated as the biggest of its kind at the Gemological Institute of Colombo, a private laboratory in Colombo.

“Looking at the reserve price of other very famous gems, I have now valued this at over US$300 million,” the owner said.

He wants to remain anonymous for fear the stone might be stolen.

Unlike blue sapphires which have complete clarity of color, blue star sapphires, a form of corundum, are opaque — but when placed under light reveal a six-line star.

Industry experts said the stone was so rare it was impossible to give a valuation.

“We can’t put a price on something like this. It is so rare and unlike other (smaller) sapphires, this is not a stone that can be replaced,” Ashan Amarasinghe, a gemologist with GIC, told AFP.

“This is something only collectors or museums can afford,” he also said.

The owner said he based his asking price on the Black Star of Queensland, a star sapphire which was reportedly sold for US$100 million in 2002, although details were not publicly disclosed.

The gem, named Lankan Star of Adam by its owner, beat the previous record for the biggest stone of its kind — also held by a Sri Lankan businessman — by about nine carats.

Both sapphires were found in Ratnapura, which is known as the island’s gem capital.

(With inputs from AFP)