The element fluorine and the word fluorescence are both named after it; George Stokes coined the second in 1852 after watching a fluorite crystal glow blue under ultraviolet light. The calcium atoms sit at the corners and face centers of the cube, and fluorine fills every one of the eight tetrahedral holes between them, an arrangement so common that it is called the fluorite structure wherever it turns up, in uranium dioxide fuel pellets and zirconia among others.
Research Elements Compound · CaF2 One unit cell, the smallest block that repeats in every direction to build the whole crystal. Atoms on its faces, edges and corners are shared with the neighboring cells. Farther atoms are drawn fainter. Atom positions from the Crystallography Open Database entry 9009005 (Wyckoff, R. W. G., 1963). In hydrothermal veins and in limestone beside galena, sphalerite and barite, as cubes and octahedra in purple, green, blue and yellow. The classic localities are the North Pennines and Derbyshire in England, where the banded purple Blue John is cut into vases, and Cave-in-Rock in southern Illinois. Most of the world's supply now comes from China, Mexico and Mongolia. Open pit and underground. The ore, called fluorspar, is crushed and sorted by density into metallurgical grade, which goes into steel furnaces as a flux that makes the slag flow (the name is from the Latin for flowing), and by flotation into acid grade of over 97% fluorite, which is turned into hydrofluoric acid for refrigerants, non-stick coatings and the cryolite baths that aluminium is smelted in.Fluorite
Elements
Crystal structure
Cell: a = b = c = 5.46295 Å, all angles 90°
Space group: F m -3 mWhere it's found
How it's mined
Notes