1 2 MINERALOGY. 



7. Mineral Matter in Vegetables and Animals. Or- 

 ganic substances are not wholly destitute of mineral 

 matters, and some have large quantities of such matter 

 in them. There is silica or flint in plants, especially in 

 the grasses ; but this is one of the most extensively dif- 

 fused of minerals, making up most of the sand of the 

 earth, entering largely into the composition of granite 

 and other rocks, and being more or less mingled up with 

 the common earth every where. Then there is carbon- 

 ate of lime, the mineral which constitutes the lime- 

 stones, the chalks, and the marbles, making up the shells 

 of the shell-fish and the skeletons of the coral animals ; 

 and phosphate of lime is the chief constituent of bone. 

 But, in these and all other similar cases, there is mere 

 deposition of mineral matter in interstices in the living 

 organs, and no real change of it into living matter. 



8. Rocks Formed from the Mineral Substances in Ani- 

 mals. Quite a large portion of the rocks in the earth 

 have been formed from the mineral remains of animals. 

 It is supposed by some geologists that this is true of all 

 which are composed of carbonate of lime. It is at least 

 extensively true of them, as we know by the remains of 

 shells and corals found in them. Much, if not all, the 

 marble in the world was once a conglomerate of such 

 remains, and was crystallized into its beautiful granular 

 condition chiefly by the agency of heat. So, also, some 

 flinty rocks are formed from the silica of the shields or 

 skeletons of animals and vegetables, for the most part 

 exceedingly minute in size. It is thus that these liv- 

 ing forms gather from the water in which they live ma- 

 terial for their structure, which, when they die, is laid 

 down to be consolidated into rock. This interesting 

 subject, barely touched fcere, will be fully treated of here- 

 after. 



9. Minerals Simple and Compound. Some minerals 

 are found in nature in their simple elementary state 

 alone, while others are found only in combination with 



