1870,] T. S. HUNT — ON GRANITIC ROCKS. 391 



to considerable variations, from a compact jasper-like rock to more 

 or less coarsely granular Tarieties, all of which are often porphy- 

 ritic from feldspar crystals, and sometimes include grains or 

 crystals of quartz. The colors of these rocks are generally some 

 shade of red, varying from flesh-red to purple ; pale yellow, gray, 

 greenish and even black varities are however occasionally met with. 

 These rocks are throughout this region distinctly stratified, and 

 are closely associated with dioritic. chloritic and epidotic strata. 

 They apparently belong, like these, to the great Huronian system. 



§ G. Many of the so-called granites of New England are true 

 gneisses, as for example, those quarried in Augusta, Hallowell, 

 Brunswick, and many other places in Maine, which are indigen- 

 ous rocks interstratified with the micaceous and hornbleudic 

 schists of the great White Mountain series. To this class also, 

 judging from lithological characters, belong the so-called granites 

 of Concord and Fitzwilliam, New Hampshire. These indigen- 

 ous rocks are tenderer, less coherent, and generally finer grained 

 than the eruptive granites, of which we have examples in the 

 micaceous granite of Biddeford, Maine, and the hornblendic 

 granites of Marblehead and Stoneham, Mass., and Newport, Rhode 

 Island, in all of which localities the contact of the eruptive mass 

 with the enclosing rock is plainly seen, as is also the case farther 

 eastward, on the St. Croix and St. John's Rivers, in New Bruns- 

 wick, and in the Cobequid Hills and elsewhere in Nova Scotia. 

 The hornblendic granites of Gloucester, Salem and Quincy^ 

 Massachusetts, seem also, from their lithological characters, to 

 belong to the class of exotic or true eruptive granites.^ The 

 farther discussion of the nature and origin of these gneisses and 

 granites is reserved for another occasion, and we now proceed to 

 notice the history of granitic veins. 



§ 7. The eruptive granitic masses just noticed, not only include 

 fragments of the adjacent rocks, especially near the line of contact, 

 but very often send off dykes or veins into the surrounding strata. 

 The relation of these with the parent mass is however generally 

 obvious, and it may be seen that they do not differ from it except 

 in being often finer grained. These injected or intruded veins 

 are not to be confounded with a third class of granitic aggregates, 

 which I have elsewhere described as granitic veinstones, or, to 



* T. S. Hunt on the Geology of Eastern Xew England, Amer. Journal 

 of Science for July 1870, p. 88 ; also Notes on the Geology of the 

 vicinity of Boston, Proc. Boston Xat. Hist. Soc, Oct. 19, 1870. 



