Open-pan salt making from lead using wood as a fuel. In Britain they established towns for salt production at Droitwich in Worcestershire, and Nantwich, Middlewich and Northwich in Cheshire. In the early Middle Ages these developed into the 'wich' towns of Cheshire. Small 'wich' houses containing several lead pans to evapourate the brine into salt, clustered around brine springs within each of the towns. The open-pan process continued largely unchanged throughout the medieval period. A 17th-century German wood-cut by Georgius Agricola shows the process in detail. Excavated evidence has uncovered wooden rakes to draw salt crystals to the side of the pan, and
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'.