While Illinois produced only 2 per cent of the 16,000,000 tons of zinc of the United States as a mine product, the zinc smelters of the state turned out 159,95S tons of zinc spelter, the largest output of any state, and 33 per cent of the total for the United States. One of the first zinc smelters in the United States was located in 1855 at La Salle, on the north edge of the Illinois coal fields nearest to the Jo Daviess County lead and zinc mines, where railroad, canal, and river transportation were at hand at that early date.
It takes so much coal to smelt zinc that it is cheaper to ship the zinc ore to the coal fields than to ship the coal to the zinc mines. For this reason the cheap and abundant coal supply of Illinois has led to the development of zinc smelters at La Salle, Peru, Depue, Springfield, Hillsboro, East St. Louis, Collinsville, Sandoval, and Danville. Thus Illinois, because of coal resources, remains a leading state in zinc smelting, although long ago the center of ore production shifted to other states. The $89,000 worth of lead and the nearly $6,000 worth of silver produced by the state are by products of the zinc mines.
Fluor spar, tripoli, and other mineral products.—Illinois produces more than 75 per cent of the fluor spar of the United States, and this output comes from the fluor-spar mines of Rosiclare, a river port on the Ohio River in Hardin County. The ore is sent by boat down the Ohio to Golconda or up the Ohio to Shawneetown, where it is loaded on railroad cars and shipped widely throughout the country. Fluor spar or "fluor ite" is used as a flux in smelting iron. It is also the source of hydrofluoric acid, which is employed for etching glass and in the manufacture of opalescent glass.
The material called tripoli is a white, or yellowish, light, porous siliceous rock. Illinois produced 77 per cent of the tripoli of the United States in 1915. Some tripoli is used as an abrasive, but most of it is worked into filter blocks. The Illinois tripoli is also used in paint, wood filter, metal polish, in soaps, in cleansers, for making glass, tile, and enamel, and for facing foundry molds.
The asphalt produced in Illinois is a by-product of the oil refineries. It finds a larger use in street paving than elsewhere.
The mineral waters of Illinois were pro duced from 23 commer cial springs, and sold at an average price of 5 cents per gallon.
About 93 per cent was sold as table waters and 7 per cent as medicinal waters.
Summary.—The coal of Illinois is of greater value than all other mineral resources combined, and it is likely to remain so. In 1915 the value of coal constituted 56 per cent of the total value of the mineral output. With the entrance of the United States into the world-war and its stimulating effect on produc tion and price of coal, this percentage of value increased to 68 per cent in 1917. Coal, petroleum, and natural gas are the mineral fuels and petroleum is the chief supply of lubricating oils. These three mineral products, once used, can never be replaced. Since the supply is limited every effort should be made to use them to the best advantage and without waste in production or consumption. Mineral resources obtained from an unlimited supply should be used where they serve as well and are as cheap as materials which are limited in amount. Limestone and shale, used in the manufacture of Portland cement, sand, gravel, and crushed rock, are among the mineral resources of this class. Illinois is fortunate in having so many mineral resources in sufficient quantities to supply her own needs, and, in some cases, a surplus to send to other states. The favorable location of Illinois with reference to the abundant iron ore of the Lake Superior district and the lead and zinc ores of the Missouri district enables her to build up great industries in these fields of manufacture on or near her coal fields. The mineral resources of the state have enabled Illinois to take high rank among the states in population, manufacturing, trans portation facilities, commerce, and wealth.