MINERALOGY. 



CHAPTER III. 



MINER ^LOGICAL CONSTITUTION OF THE EARTH's SURFACE. 



Simple Minerals : Quartz, Feldspar, Mica, Talc, Chlorite, Horn 

 blende, Serpentine, Limestone, Slate and Clay, and Augite 

 — Minerals found in Veins or Beds : Iron, Lead, Gold, Silver 

 Tin, Copper, Zinc, Mercury, Manganese, Titonium, Bismuth, 

 Antim.ony, Cobalt. 



We have now described, in a very brief manner, 

 some of the elementary substances of which the sol- 

 id as well as fluid matter of the earth is composed ; 

 and we have found that the four earths, silex, alu- 

 mine, lime^ and magnesia, constitute at least nineteen 

 parts out of twenty of the known solid matter of 

 the globe, variously intermixed and aggregated to- 

 gether. These materials form the chief proportion 

 of all loose soils, and also of the softer species of 

 stone, which are, in fact, the same substances in a 

 more compact form. Thus most kinds of sand- 

 stone are nothing more than loose sands or silex 

 cemented together; the softer kinds of slates, or 

 those which readily soften and crumble away on 

 exposure to air and moisture, are nothing more 

 than indurated clays or alumine ; and those kinds 

 of limestone which may be readily cut and worked 

 are ahnost the same thing as chalk, but in a state 

 of greater induration : while marl, which is often 

 very hard when first taken from the ground, is 

 merely an indurated admixture of argillaceous and 

 calcareous matter.* Although the varieties of 

 stones and rocks appear to be so numerous, yet, on 

 examination, we shall find that the simple minerals 



♦ Burr'8 Practical Geology. 



