BLUE John, among miners, a kind of mineral which has lately been fabricated into vases and other ornamental figures. It is of the same quality with the cubical spar, with respect to its fusibility in the fire. It loses its colour, and becomes white in a moderate heat: the weight of a cubic foot of the bluest kind is 3180 ounces, and that of the least blue is 3140 ounces. This substance began first to be applied to use about 18 years ago at one of the oldest mines in Derbyshire, called Odin mine, probably from its being dedicated to Odin the great god of the northern nations, at the foot of a high mountain called Mam-Tor in Castleton. Here the greatest quantities are still found; the largest pieces are sold for 91. a ton, the middle-sized for 61. and the least for 50s.
Prussian BLUE. See CHEMISTRY Index.