==="Blue John"===One of the most famous of the older-known localities of fluorite is Castleton in Derbyshire, England, where, under the name of Derbyshire Blue John, purple-blue fluorite was extracted from several mines or caves.
Po fluoritu sta dobila ime fluorescenca, ki je značilna za fluorite iz nekaterih nahajališč in je posledica določenih nečistoč v kristalih, in kemijski element fluor.