Rocks and Soil 



295 



Limestones are as a rule not so desirable for building purposes 

 as granite, marble, and sandstone, owing to their colors and their 

 poor working qualities. In some sections, however, limestones 

 are found that are good enough for building purposes. Certain 

 ones of a white or cream color, fine grained and readily shaped, 

 are located in southern Indiana and in northern Kentucky. Other 

 useful limestones are found in Illinois, Ohio, Iowa, Kansas, and 

 Missouri. 



Marble. Marble is a term which includes any limestone 

 capable of taking a fine polish. Its most common form is that of 

 crystalline limestone, which 

 often contains minerals whose 

 colors make it prized for or- 

 namental purposes. The so- 

 called verd antique marbles, 

 veined with green, belong 

 to this class. The color of 

 marble varies from white 

 through intervening shades of 

 gray to black. Pink, red, and 

 brown marbles are also quite 

 common, the colors being due 

 to the presence of iron oxides. 



The main sources of mar- 

 ble in the United States are the 

 older beds of limestone lo- Brown Brothers, 



cated in the vicinity of the A MARBLE QUARRY 



Appalachian mountain system. The state of Vermont furnishes 

 over 50 per cent of it. Other eastern states supply marble for 

 building. The chief source of colored decorative marble is eastern 

 Tennessee. The most beautiful and highly prized of all marbles is 

 the so-called onyx marble. It was formerly found only in Egypt, 

 Algeria, and Mexico, but is now found in California and Arizona. 



Cement and Concrete. In recent years cement and concrete 

 have been used increasingly in place of wood, rock, and metal for 

 important structures. Everywhere we have examples of 

 their use in buildings, roads, bridges, sidewalks, and fence posts. 



