History of Northwich in the early medieval period is shown by its record in the Domesday Book: It shows that by 1086 the town was producing salt and was valued the same as Middlewich at £8, although less than the £21 value given to Nantwich. It is unclear if salt extraction had continued from the Roman to Medieval periods. The manor of Northwich belonged to the Earls of Chester. However, in 1237 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. By 1484 this family
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'.