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SKETCH OF THE 



In describing the various individuals of this class, different adjuncts, 

 illustrative of their composition, shall be used, and in this view of the 

 case, the granitic rocks may be divided into the following varieties ; 



First. — Granites composed of three ingredients. 



A. — Common Granite — composed of quartz, felspar, and mica. 



B. — Sienitic Granite — composed of quartz, felspar, and hornblende. 



c. — .Talcose Granite — composed of quartz, felspar, and talc or steatite. 

 D. — Chloritic Granite — in which chlorite replaces the mica. 



Second.— Qom^osedi of four or more ingredients. 



A. — Micaceous Sienitic Granite — Sienitic granite, with the addition 

 ' of mica. 



B. — ^Talco Sienitic Granite — ^the same as the above, the mica being 

 replaced by talc or steatite, &c. &c. &c. 



Third. — Granites composed of two ingredients. 



Under this head shall be included rocks, which might perhaps be 

 classed with the compact and granular felspars. The term white stone, 

 applied to the latter by Werner, is not well adapted for this rock, as it 

 frequently occurs in this district .—Names derived from color, are always 

 objectionable, and, as this rock is here found more frequently of a red- 

 ish color than of any other, I prefer giving it the name of granite, more 

 especially as some other ingredient is almost universally associated with 

 the felspar, whether compact or granular, and these pass into, and are in- 

 timately connected with, the granites-^when they occur pure, the circum- 

 stance shall be mentioned. I do not feel myself called upon, or at all 



