MINERALOGY. 44' 



FIRST ORDER. 

 CARBON. 



The first of this race of minerals is 



Stone Coal. Mineral coal occurs either in compact 

 masses, or detached portions, in beds or layers of differ- 

 ent sizes, interstratified with other rock strata, as clay 

 shales and coarse grit sandstones. Mostly sectile, 

 sometimes brittle; color grayish-black, of shades more 

 or less intense. Luster vitreous, resinous, sometimes 

 sub-metallic, opaque ; often rendered impure by admix- 

 ture with clays, and always associated with sulphur 

 (pyrites). H. = 2 to 2.5. G. = 1.1 to 1.5. Bitu- 

 minous coal ignites easily, and burns with a bright lively 

 flame ; anthracite, called stone-coal, affords only a pale 

 blue, sulphurous light. If coal is burned in a close 

 receptacle, and the atmospheric air is wholly shut off, 

 gas is evolved, and the residue, rough, ponderous, ex- 

 tremely hard, and highly combustible, forms coke, 

 which is of infinite use in the smelting of metals. 



Mineral coal occurs in extensive beds or layers be- 

 tween the clay shales and sandstones, principally those 

 of the sedimentary and old red sandstone formations. 

 The strata vary in thickness from a few lines to forty 

 feet. This useful mineral is very widely distributed 

 over the world. England, France, Spain, Belgium, 

 Germany, especially in the region of the Rhine, the 

 Saale, the Elbe, and the Oder. But nowhere is the 

 coal formation more extensively displayed than in the 

 United States, nowhere are its beds of greater thickness 

 or its qualities more valuable. East of the Alleghanies 

 the coal is of the hard, compact species known as anthra- 



