REVIEW OF THE GRANITES BY STATES 381 



eastern Pennsylvania, but regarding massive granites little information 

 is recorded. 



Maryland. — The granites of Maryland conform quite closely to the 

 biotitic types. They show some variation from them in the presence of 

 epidote in such relations that it is regarded as an original mineral by 

 C. R. Keyes. Biotite is, however, always associated with it. Muscovite- 

 granites are quite uncommon, and varieties with hornblende are notice- 

 ably rare. The chemical composition of the Maryland * granites has 

 been more fully investigated than that of other states as yet. Seven 

 analyses in all are available. They vary somewhat widely in the amounts 

 of potash, soda, and lime which are present. In but two cases, namely, 

 Woodstock and Brookville, does the molecular ratio of potash exceed 

 that of soda, and then only slightly. In the others the molecular ratio 

 of the soda is in marked excess, and in the Port Deposit stone it is nearly 

 three times as much In these latter cases the granites exhibit tendencies 

 toward the quartz-mica-diorites. 



Virginia. — So far as recorded,, the Virginia granites are all of the bio- 

 titic type. Both in the hand specimen and in thin- section they resemble 

 the finer-grained, gray biotite-granites of the areas further north. 



North Carolina. — Granites are abundant in this state and are quite 

 extensively quarried. The Tenth Census did not, however, tabulate 

 the determinations of them. G. P. Merrill f has given some notes upon 

 their character and distribution, but not always with mention of the 

 mineralogy. Statistics can not, therefore, be compiled, but it is apparent 

 from this record, and the writer has also learned from his colleague, 

 Doctor A. A. Julien. whose acquaintance with the petrography of North 

 Carolina is extensive, that biotite-granites are abundant, and that other 

 varieties are also present. 



South Carolina. — Granites are known to occur in South Carolina, but 

 their mineralogic characters are not yet a matter of record. 



Georgia. — ^In two localities in Georgia muscovite-biotite-granites are 

 extensively quarried, Stone mountain and Lithonia. The huge doming 

 ridge of Stone mountain is in fact one of the most striking geological 

 phenomena of the East. Muscovite prevails over biotite in the rock, 

 although the latter is fairly abundant. There are doubtless many other 



*G. H. Williams: The general relations of the granitic rocks of the middle Atlantic Piedmont 

 plateau. XV Ann. Rep. Director U. S. Geol. Survey, 1895, p. 657. 



C. R. Keyes : Origin and relations of the central Maryland granites. Idem., p. 685. 



G. P. Grimsley : Granite of Cecil county, in northeastern Maryland. Jour. Cincinnati. Soc. Nat. 

 Hist., vol. xvii, 1894, pp. 56-67, 87-114. 



E. B. Matthews : Report on Blaryland building stones. Maryland Geological Survey, vol. ii, 1898, 

 pp. 136-160. Doctor Blatthews also gives an excellent bibliography on p. 131. 



t Stones for building and decoration, 1897, pp. 257-260. 



