KINDS OF ROCK. 43 () 



The distinctions as to kinds of rocks between metamorphic and 

 eruptive granites are not yet made out. A porphyritic variety, having 

 the base fine-grained, occurs east of Parkview Peak, in the Rocky Mts. , 

 which, according to Hague, is eruptive and related to the trachytes of 

 the region. The granite of New England is for the most part meta- 

 morphic or in veins. The following are prominent regions of the 

 granite quarries. In Maine : at Hallowell, a whitish granite, some- 

 times a little gneissoid ; at Rockport, whitish ; at Clarke's Island, 

 spotted gray ; at Jonesbury, fiesb-red ; also in the Mt. Desert region! 

 In New Hampshire, at various places, but most prominently near Con- 

 cord, a fine-grained whitish granite. In Massachusetts at several 



at Groton, near New London, a fine-grained whitish granite ; at Stoney 

 Creek, a pale reddish, but liable to large micaceous spots ; at Ply- 

 mouth, on the Naugatuck, a whitish granite, even and fine-grained, 

 more easily worked than the Westerly. 



2. Granulyte. (Leptinyte.) — Like granite, but containing 

 no mica, or only traces. Metamorphic and eruptive. 



Varieties. — a. Common granulyte ; white and usually fine granu- 

 lar, a common rock in Western Connecticut and Westchester Co., New 

 York. b. Flesh-colored; usually coarsely crystalline, granular, and 

 flesh-colored ; the coarse flesh- colored "granite" of the Eastern or 

 Front Range of the Rocky Mts. , in Colorado, sometimes called Aplite, 

 is partly of this kind ; it contains a little albite or oligoclase with the 

 orthoclase. c. Garnetiferous. d. Rornblendic ; containing a little 

 hornblende — a variety that graduates into syenyte. e. Magnetitic ; 

 containing disseminated grains of magnetite, a kind common in 

 Archaean regions, in the vicinity of the iron ore beds, occurring in 

 Orange Co., N. Y., and south in New Jersey, and also at Brewster's, 

 Dutchess Co., N. Y., and in Kent and Cornwall, Conn. f. Grapltib 

 (Pegmatyte) ; like gr. ^hic granite, but containing no mica. The 

 coarser granulyte, especially that of veins, is often called pegmatyte 

 when not graphic. 



3. Gneiss. — Like granite, but with the mica and other 

 ingredients more or less distinctly in layers. Gneiss breaks 

 most readily in the direction of the mica layers, and hence 

 its schistose structure ; in consequence of this structure, 

 many kinds may be got out in slabs. It often graduates 

 imperceptibly into granite. Metamorphic. 



Varieties. — Similar to those under granite, a. Porphyritic. b. Al- 

 hilic. c. Oligoclase-bearing. d. EornUendic. e. Micaceous, f. Globu- 

 liprous. g. Epidotic. h. Garnetiferous. i. Andalusitic; contains an- 

 dalusite in disseminated crystals, j. Cyanitic ; contains cyanite, a 

 variety that has been observed on New York Island, and also in New- 

 town, Ct., Bellows Falls and elsewhere in N. H. k. Graphitic; con- 

 tains graphite disseminated through it. 1. Quartzose ; the quartz 

 largely in excess, m. Quartzytic ; consists largely of quartz in grams, 

 being intermediate between quartzyte and gneiss, a variety occurring 

 just northeast of Bernardston, Mass. Fig. 3 on page 415 represents, 



