THE FORMATION OF MINERALS AND ROCKS

The natural formation of minerals, and consequently of rocks, takes place in a wide variety of ways, both in the earth and at the surface. In figure 7.3 some of these processes with the accompanying temperatures and pressures in the various layers are shown. 

When foreign building blocks of roughly equal sizes are present during the crystallization process, these can be incorporated and in this way so-called mixed crystals are formed (fig.7.5) 

Mineral formation as a result of weathering will be discussed in chapter 8, which deals with the formation of clay. 

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