Blue John is native to Treak Cliff, Derbyshire, where there were four mines. It is a variant fluorspar which has been coloured in veins, over millions of years, with natural minerals and chemicals such as oil, iron and uranium, thus it has a wide colour range from deep purple through to golden yellow, cream to blood red. It may have been first discovered by the Romans and known as vasa murrina and subsequently rediscovered in the mid-18th Century. It was mined in seams, usually about 4in. wide, so to produce a large piece of Blue John was rare indeed. Shaping Blue John after chiselling out the basic form and smoothing the surface was done by heating and applying a metal tool while on a lathe. Blue John proved so popular and was mined exhaustively during the late 18th and early 19th Centuries, until it is said that there is only enough left in some mines to last until the year 2000.