INTEiniEDIATE CHARACTER OF APPALACHIAN- GRANITES 9 



On a more generalized basis the seven divisions of the table can be 

 reduced to three as follows: (1) Mica granites, including I, II, III, V, 

 and VI, in which some hornblende (III) and epidote (VI) are associated 

 with the mica (biotite) ; (2) hornblende granites (IV) ; and (3) epidote 

 granites (VII). On this interpretation the totals are: Mica granites 728, 

 or 91.3 per cent.; hornblende granites 63, or 8.5 per cent., and epidote 

 granites 6, or less than 1 per cent., which strongl}' emphasizes the pancity 

 of types other than mica granites. 



Hornblende is only occasionally met with and hornblendic varieties of 

 granite are relatively rare. It is noted alone or associated with biotite, in 

 the granites of Maryland at one locality in northeastern Cecil county, and 

 again near Washington in the vicinity of Garrett Parle; in Virginia, in a 

 part of the granites south of Falls Church, Fairfax county, and with biotite 

 in the granites near Saxe, in Charlotte county ; in Korth Carolina, in some 

 of the granites of Mecklenburg county ; in South Carolina, in the granite 

 occurring one mile south of Winnsboro, Fairfield county, where hornblende 

 is subordinate to biotite ; and in Georgia, in the Armour's Mill area, Putnam 

 county, of sheared fine-grained granite, and near Grantville, Coweta county. 

 Though a common constitiient in man}^ of the more massive and schistose 

 basic rocks abundantly distributed throughout the crystalline region, 

 hornblende is equally as rare in the acid gneisses as in their massive equiv- 

 alents. It is associated with biotite in the coarse-textured granite-gneisses 

 around Eichmond and Fredericksburg, Virginia. 



Epidote occurs in such relations in some of the Maryland granites as to 

 be regarded an original constituent by some students,^ and is present in suffi- 

 cient amount for the rocks to be grouped as biotite-epidote granites. It is 

 often present as a secondary mineral, usually in microscopic quantity only. 

 in the gTanites of the states south of Marjdand. In Madison, Page, and Car- 

 roll counties, Virginia ; Madison county. North Carolina ; and Cocke county, 

 Tennessee, epidote is a chief constituent in the epidote variety of granite, 

 known as unakite. In each of these localities the epidote^ has been shown, 

 from microscopic study, to be a secondary mineral. 



Various accessor)^ minerals are known, among which apatite, zircon, iron 

 oxide, and in many localities, more especially in Maryland and South Caro- 

 lina, titanite, are the commonest ones. AUanite is a frequent accessor}^ 



H5th An. Kept., U. S. Geol. Survey, p. 685. 



Watson, Thomas L. Journ. Geology, 1904, Vol. XII, pp. 395-398; Ainer. Journ. 

 Science, 1906, Vol. XXII, p. 248. Phalen, W. C. Smithsonian Misc. Coll., 1904, 

 Vol. XLV, pp. 306-316. 



