Burmese politican U Tint Soe stands next to the giant gem at the remote mine in Kachin State Credit: SWNS 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 s