Sri Lankan authorities on Sunday put on show what they said was the world’s largest natural corundum blue sapphire, weighing 310 kilogrammes, which was found in a gem pit about three months ago. Local gemologists, who have examined the sapphire, said it was one of the rarest gems in the world as it weighed more than 300 kilogrammes. International organisations are yet to certify the precious stone. The sapphire was put on display at the home of one of the gem pit owners in Horana, 65 kilometres south of Colombo. A group of Buddhist monks chanted blessings for the gemstone before it was unveiled. The stone was found in the gem-rich Ratnapura area where local people had previously found the world’s largest star sapphire cluster in a backyard by accident. Ratnapura is known as the gem capital of the South Asian country, which is a leading exporter of sapphires and other precious gems. The country earned around half a billion dollars through the export of gems, diamonds and other jewellery last year, the local gems and jewellery industry body has reported.