396 Eggleston — Eruptive Rocks at Cutting sville, Vt. 



draw a line between the two in mapping their respective 

 areas. It is possible that there is no such line, and that 

 the pulaskite and nordmarkite are really one body, more 

 augitic and nordmarkitic on the north and more feld- 

 spathic and pulaskitic on the south. 



Coarse-grained phases of pulaskite are very strikingly 

 developed near the crest of the middle part of Granite 

 Hill. It occurs as ill-defined apparently northward- 

 trending streaks or schliers, about a foot wide, in sydnite 

 not quite so coarse. The rock is practically all feldspar, 

 in chunks or rough crystals, some upwards of 2 inches in 

 length. 



A noteworthy point about some of the coarse-grained 

 phases of the Cuttingsville eruptives is their proximity 

 to eruptive contacts, suggesting that their coarseness of 

 grain is partly due to the action of gases emanating at 

 contacts. 



Biotitic phases of the pulaskite develop near contacts 

 with" essexite. This is notably the case on the north knob 

 of Granite Hill, and in the exposures along Mill River at 

 the east foot of the south knob. 



A peculiar coarse biotitic phase is developed in small 

 amount between essexite and normal pulaskite in the pit 

 (P, fig. 1) south of the quarry. Similar rock, with the 

 same association of essexite and normal pulaskite and in 

 limited amounts, is exposed on the path near the quarry. 

 Penetrating the usual coarse, hypidiomorphic gray-white 

 feldspars are skeleton flakes of biotite up to one inch 

 in diameter. The flakes are quite numerous and lie in 

 various attitudes. Consequently a broken surface of the 

 rock shows a number of roughly radiating black lines, 

 which are the traces of the wide flakes broken across. 

 Besides these, some flakes, luster-mottled as a result of 

 their skeletal structure, appear full face. 



Fine-grained and porphyritic phases of pulaskite 

 appear frequently along contacts. 



The pulaskite of the two small eruptive areas (fig. 1) 

 north of the Granite Hill area is mostly medium 

 grained. 



Sodalite-nephelite Syenite (4, fig. 1). — The sodalite- 

 nephelite syenite at the railroad cut is a holocrystalline, 

 moderately coarse-grained aggregate of light-gray feld- 

 spar of tabular habit, rather frequently in Carlsbad 

 twins, with interstitial black pyroxene and brownish 



