Fluorite is calcium fluoride, and it is unusually important to science for a soft ornamental mineral. It gave its name to two phenomena: fluorescence, the glow of certain fluorite specimens under ultraviolet light, named after the stone by George Stokes in 1852; and the element fluorine, first isolated from it. It is the reference point for hardness 4 on the Mohs scale, has perfect octahedral cleavage that lets it be split into clean eight-sided pieces, and occurs in nearly every colour, purple being among the most prized. As a flux in smelting, the Latin fluere, to flow, is the root of the name, it has a long industrial history, and the banded blue-purple Blue John of Derbyshire was carved into Georgian ornaments. Its metaphysical placement, typically with mental clarity and the higher centres, is a modern colour-and-name-led assignment, not a traditional one.
Fluorite has long been carved in China as an inexpensive stand-in for jade and other harder stones; called yingshi in Chinese lapidary tradition, banded and coloured fluorite was cut into snuff bottles, small vessels and figures from at least the Qing dynasty onward, prized for taking a high polish despite its softness. In Europe the same softness was turned to different use in Derbyshire, England, where a rare banded purple-and-yellow fluorite called Blue John was mined from a single hill, Treak Cliff, and worked into vases and ornaments from the eighteenth century, a British industry now nearly exhausted of its raw material.