Two men have been arrested on suspicion of stealing an estimated 60kg (132lb) of a rare semi-precious mineral in the Peak District.
Police said a large quantity of Blue John was recovered from an address in Greater Manchester on Tuesday night following a report of theft in Castleton, Derbyshire, on 13 October.
The county’s rural crime team said the mineral was unique to the area and not found anywhere else in the world.
The two men were separately detained in Bury and Oldham on suspicion of theft and have been released pending further investigation, the team said.
Blue John is only found beneath Treak Cliff Hill, near Castleton, and gets its name from its distinctive colour.
It is now only mined in two caverns – Treak Cliff Cavern and Blue John Cavern.
The stone was fashionable during the Regency period in the early 1800s and is displayed at Buckingham Palace and Chatsworth House.
Officers said: “The site is Site of Special Scientific Interest (SSSI) protected and quarrying of Blue John is strictly controlled.
“Theft of this rare fluorite not only harms the natural environment of the site and local economy, but it also harms the site’s heritage.
“It is sometimes said that Blue John was first discovered by the Romans.”
Police added the items would be assessed by an expert to determine their value.
