Blue John is quite a rare varity of Fluorite , which can be found in a multitude of colours , hence the name The Rainbow Mineral.
Blue John is a purple blue variety of Fluorite , mined exclusively in the Castleton area of Derbyshire . It was formed largely during the Carboniferous geological period , 350 million years ago , from highly saline solutions , seeping into rocks deep below the surface and crystallizing there .
The Derbyshire region relied on the mining of Blue John , since its discovery in 1766, as it became very popular during the Victorian period due to its beautiful colourations and patterns.
It is a birthstone for Pisces and Capricorn . It may calm anxiety , bring clarity , strengthen compassion and respect.