NOME VII. D. GRANITE. 245 



mountain had not been decomposed, perhaps 

 these precious mines would not have been dis- 

 covered. 



On a smaller scale, the most usual decompo- 

 sition of granite is where the felspar assumes the 

 appearance of bole or lithomarga, of porcelain , 



earth, or of fine clay. The noted Kaolin of the Kaolin. 

 Chinese forming a chief ingredient of their 

 famous porcelain manufactures, is a decomposed 

 felspar, which seems mostly to proceed from an 

 entire rock of that substance, as there seems to 

 be no quartz ; while that of Limoges, in France, 

 the chief ingredient of the Sevres manufacture, 

 may have been a granite in which the micarel is 

 also decomposed ; for there are numerous grains 

 of quartz, which are carefully separated. 



Granite, decomposed by volcanic heat, is 

 common in Auvergne, where the lava has 

 burst through superincumbent masses of that 

 substance ; but such appearances may rather be 

 ranked among the volcanic ; the decomposition 

 here chiefly treated, being that effected by the 

 influence of time and climate. Karsten has 

 given the following examples of decomposed 

 granite. 



