Miners in Burma have unearthed one of the world's most valuable pieces of jade - an 18ft stone worth £140million.

Workers were excavating rare gems at a remote mine in Kachin State when they stumbled across the gem stone.

The rock, weighing 175 tonnes and measuring 9ft high and 18ft long, is second only in size to the carved statue at the Jade Buddha Palace in China which weighs 260 tonnes.

Burma - or Myanmar - is the world's largest producer of jadeite - and the 50 billion dollar a year industry represents half of the country's GDP.

The boulder will be sent to China where it will be carved up into expensive jewellery and sculptures.