Northwich was the most northern of the -wich towns in Cheshire. The existence of Northwich in the early medieval period is shown by its record in the Domesday Book: The manor of Northwich belonged to the Earls of Chester until 1237 when the family line died out. Subsequently, Northwich became a royal manor and was given to a noble family to collect tolls in exchange for a set rent. That salt production continued throughout the centuries and can be seen through John Leland's description of the town in 1540: Between 1642 and 1643, during the English Civil War, Northwich was fortified
Blue John (mineral) Blue John (mineral) Blue John (also known as Derbyshire Spar) is a semi-precious mineral, a form of fluorite with bands of a purple-blue or yellowish colour. In the UK it is found only at Blue John Cavern and Treak Cliff Cavern at Castleton in Derbyshire. During the 19th century, it was mined for its ornamental value, and mining continues on a small scale. Deposits of fluorite have been recently found in China with colouring and banding similar to the classic Blue John stone. The most common explanation for the name is that it derives from the French "bleu-jaune", meaning 'blue-yellow'.