London: A giant jade boulder that could be worth billions of pounds has been discovered in Burma.

The 50-tonne block was found half buried in soil and rock in the gem-rich north of the country.

Villagers discovered the 5.5 metre-wide boulder in the mountainous state of Kachin, where rebels have been fighting the government for more than 50 years. It is now under armed guard as officials negotiate with rebels about what to do with it.

Burma, also known as Myanmar, is one of the world’s biggest producers of precious stones.

Jade expert Jason Holt, of Holts Jewellers in Hatton Garden, London, said the find was astonishing.

“The very best imperial jade can be worth hundreds of thousands of pounds for a piece that would fit into the palm of your hand,” he said.

“If it is the top, top quality, then you are talking about billions of pounds.”