This small, copiously illustrated book claims to present the only comprehensive account of Blue John ever written. After an introduction and a definition of Blue John as fluorite with blue or purplish blue crystalline layers alternating in crystalline masses with white or yellowish layers, the world famous deposits of Blue John at Castleton are introduced via the mineral deposits of the Peak District, leading on to the deposits in and around Treak Cliff. The various ‘veins’, each characterized by slightly different patterns of colour banding in the Blue John are described, and it is pointed out that these are not...

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