MINERALS AND ORES 



171 



193. Feldspar. Feldspar contains the same elements as 

 quartz and, in addition, the elements of lime or soda and of 

 alumina (a very hard mineral, sometimes known as corundum 

 or emery). Feldspar is not so hard as quartz, is fusible, and 

 on being exposed to the air crumbles to clay. Clay is found 

 in many soils, where it furnishes some elements required by 



FIG. 85. JAMES DWIGHT DANA: GEOLOGIST. 1813-1895 



The characteristic that most impressed all who came to know him, 

 whether through the reading of his works or through personal intercourse, 

 was his profound sense of the sacredness of truth. . . . Even to extreme 

 old age he remained hospitable to new truth and ready to change opinions. 

 Disloyalty to truth was infidelity to God. In his scientific investigations 

 he always felt, like Kepler, that he was thinking God's thoughts after him. 

 WILLIAM NORTH RICE in Leading American Men of Science. 



plants. Because of its fusibility, feldspar is common in 

 volcanic rocks; these rocks on decaying make fertile soil. 



Common crockery is made from white clay, pressed into 

 shape and baked. Powdered feldspar is used to make the 

 glazing for the surface. There are feldspar quarries in 



