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.