History of Northwich was the Stanley's, later Earls of Derby and stayed in the family’s hands until the late 18th century. That salt production continued throughout the centuries can be seen through John Leland's description of the town in 1540: Although Leland described Northwich as a market town, there is no surviving charter for a market or fair. A market still exists today. Between 1642 and 1643, during the English Civil War, Northwich was fortified and garrisoned by Sir William Bereton for the Parliamentarians. The salt beds beneath Northwich were re-discovered in the 1670s by employees of the local Smith-Barry family. The Smith-Barrys
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'.