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ROCKS AND SOIL 



made up of particles, some large, some tiny. Each of 

 these substances out of which rock is formed has a different 

 chemical composition and is called a mineral. Sulphur 

 is a mineral containing a single chemical element, while 

 table salt or a grain of white sand is a mineral each made 

 of two elements combined in compounds. Granite, on 

 the other hand, is made up of several minerals in which 

 quartz and feldspar are always present. Rocks usually 

 contain several minerals, but some, like the rock salt, are 

 single minerals. The name of the mineral, salt, is halite, 

 and when freed from impurities, we use it to season our 

 food. Mica is an interesting mineral. Some mica is 

 white and some is black in color. It has the remarkable 

 quality of splitting off in very thin almost transparent 

 sheets. It is often incorrectly called isinglass. It is used 

 as an insulator in electric devices and for windows in 

 doors of stoves. 



Rocks and Minerals Are of Different Hardness. If 

 you take a number of different minerals, such as quartz, 

 feldspar, mica, rock salt, talc, gypsum, and others, you 



Wright Pierce 



This shows how the hardest rocks (granite) may be weathered to form soil, 

 has probably caused this rock to break down ? 



What 



