Fluorite - Fluor Spar Composition, Crystallization & Structure

Composition. Calcium fluorite, CaF2 = Fluorine 48.9, calcium 51.1.

Crystallization. Isometric. Habic cubir often in twinned cubes other form are rare, but examples of all the forms of the Normal Class have been observed; the tetrahexahedron and hexoctahedron are characteristic.

Structure. Usually crystallized. Also massive; coarse or fine granular, columnar.

Physical Properties. Perfect octahedral cleavage H. = 4. g. = 3.18. transparent to subtranslucent. Vitreous luster. Color widely various; most commonly light green, yellow, bluish green or purple, also colorless, white, rose, blue, brown. A single crystal may show varying bands of color; the massive variety is also often banded in color. The bluish green varieties often show fluorescence (green by transmitted light, blue by reflected light). Some varieties phosphoresce when heated, giving off variously colored lights which are independent of the actual color of the specimen. The variety affording a green light is known as chlorophane.

Test. fusible at 3, and residue gives alkaline reaction to moistened test paper. Gives a reddish flame (calcium). When mixes with potassium bisulphate and heated in C.T., hydrofluoric acid is evolved which etches the glass, and a white deposit of silica forms upon the walls of the tube. Determined usually by its cubic crystals and octahedral cleavage, also vitreous luster and usually fine coloring, and by the fact that it can be scratched with a knife.

Occurrence. A common and widely distributed mineral. Usually found either in veins in which it is the chief mineral or as a gangue mineral with metallic ores, especially those of lead and tin. Common in dolomites and limestones and has been observed also as a minor accessory mineral in various igneous rocks.- associated with many different mineral, as calcite, dolomite, gypsum, celestite, barite, quartz, galena, sphalerite, cassiterite, topoaz, tourmaline, apatite.

The more important deposit in the United Status are in southern Illinois near Rosiclare, and in the adjacent part of Kentucky. The fluorite occurs here in limestone, in fissure veins which at time become 40 feet in width. Fluorite is found in quantity in England, chiefly from Cumberland, Derbyshire and Durham; the first two localities being famous for their magnificent crystallized specimens. Found commonly in the mines of Saxony. Fine specimens come from Switzerland, the Tyrol, Bohemia, Norway, etc.

Use. Fluorite is used mainly as a flux in the making of steel, in the manufacture of opalescent glass, in enameling cooking utensils, for the preparation of hydrofluoric acid, and occasionally as an ornamental material in the from of vases, dishes, etc.