Fluorite has given two words to the language and both came from watching it behave.
The first is flux. Fluorite is calcium fluoride, it melts at a relatively low temperature, and it was added to metal ores to make the slag run freely. The name comes from Latin fluere, to flow, and the mineral is still used in enormous quantities in steelmaking for exactly that purpose, as well as being the principal source of fluorine and of hydrofluoric acid.
The second is fluorescence. Many fluorites glow, typically blue or violet, under ultraviolet light. George Gabriel Stokes described the effect in 1852 and named it after the mineral in which he had been observing it, so every fluorescent lamp and every fluorescent dye is named, at one remove, after this stone. Not all fluorite fluoresces, and the ones that do owe it to trace rare earth elements rather than to the calcium fluoride itself.
The purple banded variety from Castleton in Derbyshire, Blue John, was worked into vases and urns in the eighteenth and nineteenth centuries and is found in only that one small area. It is sometimes proposed as the material of the Roman murrina vessels that Pliny describes as extravagantly costly, but the identification is disputed and the ancient descriptions do not settle it.
Fluorite is soft, four on the Mohs scale, and it has perfect cleavage in four directions, which means it can be cleaved into octahedra and that it is a poor material for anything that will be worn.