Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. Mohs scale of mineral hardness, based on scratch Hardness comparison, defines value 4 as Fluorite.
In its pure variant, the mineral is transparent, but it can be tinted with elemental impurities. Therefore it comes in a wide range of colours and has consequently been dubbed "the most colourful mineral in the world". The most common colours are purple, blue, green, yellow, or colourless. Less common are pink, red, white, brown, and black.
Fluorite is a widely occurring mineral with significant deposits in over 9,000 areas globally. With the largest deposits being in South Africa, Mexico, and China, it can also be found for example in Mongolia, Russia, Spain and Namibia. 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.
Source: en.wikipedia.org/wiki/Fluorite - 23.10.2017