Massive Crystalline Rocks. 63 



on the other. It occurs along the railroad between Peekskill and 

 Montrose station, and over the most of the town of Cortland east of 

 this line, and to some extent west. 



This rock passes into a felspathic kind {Bh), consisting almost 

 wholly of the felspars ; and into a micaceous kind (Be) containing 

 very much black mica with little hypersthene — a very common 

 variety, often occurring close alongside of the ordinary norite. 



Although the norite is generally a massive rock, it is occasionally 

 distinctly gneissic in structure, and sometimes contains a few garnets. 

 The schistose variety usually abounds in black mica, or contains 

 more quartz than other varieties, and sometimes more orthoclase. 



C. The Augitic. — True augitic rocks are less common than hyper- 

 sthene rocks, although augite is present in most of the massive rocks 

 of the Cortland region. The chief kind {Ga) is pyroxenite — con- 

 sisting mainly of pyroxene or augite, with sometimes a little horn- 

 blende ; it varies from a very coarse rock with the augite crystals 

 half an inch across, to a fine granular kind. A greenish-grey 

 granular variety occurs on Stony Point in its chi'ysolitic region. 

 Another kind (C&) contains much triclinic felspar with the augite, 

 and is here called augite-norite} A local variety ( Cc), related to 

 the last, is light-grey in colour and smooth in fracture ; it has 

 a whitish felspathic base, seemingly almost felsitic, speckled with 

 small spots or points of dark grey-green augite, and only traces of 

 mica. The felspar in this variety, as slices show, is actually in 

 fine crystalline grains ; almost all of it is triclinic, as in other 

 varieties. Chrysolitic kinds are mentioned beyond. 



D. The Micaceous. — The micaceous rocks are of two prominent 

 kinds. One {Da) is like a coarse granite in aspect ; but its fels- 

 pathic portion is chiefly triclinic, and quartz is sparingly present. 

 It is characteristically a soda-lime granite, although containing some 

 orthoclase, and it is a nearly quartzless variety of it. The mica is 

 almost solely biotite or black mica. It is called beyond soda-granite. 

 Some hornblende or augite is usually present ; and apatite is 

 common in small or minute disseminated crystals. It is sometimes 

 sparingly garnetiferous. Good examples of this rock occur west of 

 Cruger's railroad station above the brick yards ; and also at Stony 

 Point, where it is the prominent rock. At the former locality it 

 graduates into the quartz-diorite ; and at several places the coarsest 

 of the diorite is found within a few yards of the typical soda-granite. 



Another kind {Bh) is a fine-grained black rock, often small- 

 porphyritic. It owes its colour and texture to its having black mica 

 in fine scales as its chief constituent. Like the preceding, it contains 

 little quartz, and the felspar is almost wholly triclinic. Hornblende 

 and augite are sparingly present. The rock is therefore a micaceous 

 variety of the soda-granite. But, though ordinarily massive, it 

 sometimes has distinct indications of bedding. The rock is most 

 common in the vicinity of limestone belts. It occurs at Centerville, 



1 This rock looks like the norite, but contains augite in place of hj'persthene. If 

 its felspar is chiefly labradorite (a point yet in doubt) , it does not differ in mineral 

 constitution from dolerite or diabase, or a prominent part of the so-called gabbro. 



