Nature Bulletin No. 361-A   December 6, 1969
Forest Preserve District of Cook County 
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

****:FLUORSPAR

Among all the states, Illinois stands at the top or very near the top in 
its production of corn, hogs, soybeans, oats and chickens. The same is 
true in industries: meat packing, steel, agricultural machinery, 
tractors, radios, telephones, paint, candy and many others. It is one of 
the leading producers of coal. Not commonly known, however, is the 
fact that the world's largest fluorite mines are located in Pope and 
Hardin counties along the Ohio River, and few people realize what an 
important part this mineral plays in our daily lives.

Chlorine, bromine, iodine and fluorine are chemical elements always 
found in combination with some metal. Common salt is chloride of 
sodium. Fluorspar, or Fluorite, is fluoride of calcium. Although quite 
common, occurring in several states and in foreign countries, there are 
few deposits with veins large enough to be mined commercially. 
Almost half of what is used in this country comes from southern 
Illinois and most of the remainder from Kentucky, just across the 
river. It is mined from veins as much as 800 feet below the surface.

In many respects, fluorspar is one of the most remarkable of minerals, 
and one of the most useful, but people seldom hear about it because it 
is mostly used to help make something else, as a "silent partner". 
Geologists call it "the most versatile servant of industry". Its name 
comes from a Latin word meaning: "I flow". About 1888, when the 
open-hearth process of making steel came into use, it was found that 
the addition of a small quantity of fluorspar as a fluxing agent speeded 
up the process, saved fuel and produced purer better steel. It enables 
operation of the furnace at lower temperature, changes the slag from 
an unmanageable mass to a fluid substance easily drawn off, and 
removes sulfur or other impurities. Until recent years, the steel 
industry used most of all fluorspar mined. Formerly, the manufacture 
of aluminum depended upon the only known deposit of "cryolite" -- 
sodium aluminum fluoride -- in Greenland. Synthetic cryolite, made 
from fluorspar, is now the key to our vast production of cheap 
aluminum.

Forty years ago, hydrofluoric acid was used chiefly for etching glass 
and in insecticides. Made by treating fluorspar with sulfuric acid, it is 
one of the most corrosive substances known and had to be kept in lead 
containers. Today, it is the key material in the manufacture of 
high-octane gasoline for aviation, an important group of plastics, 
insecticides, and the refrigerants known as Freons -- ideal for use in 
homes and public places because they are colorless, odorless, non-
poisonous and non-inflammable.

Fluorspar plays an important part in the manufacture of glazed tiles; 
enamel coatings on steel for stoves, refrigerators, table tops, counters 
and other equipment for such places as kitchens and bathrooms; 
opalescent glass for light bulbs, lamp shades and soda fountains; 
abrasives; and special lenses for the optical industries. The uses for 
this Jack-of-many-trades are almost endless.

Fluorspar crystals are usually cubes, as in salt, and it is one of the most 
beautiful of all minerals. None other varies so widely in shades and 
tints of many colors: white, amethyst (most common), blues from light 
azure to ultramarine, purple, yellow, red, brown and even black -- 
depending upon the iron manganese or other impurities present. Some 
varieties glow in an invisible ultraviolet light, and hence our term 
"fluorescent". It mars too easily to be used for jewelry, although the 
Mound Builders carved it into statuettes and ornaments and a big pink 
slab of fluorspar has long served as the doorstep to the old Kinkaid 
home on the Ohio River.