Eggleston — Eruptive Rocks at Cutting 'sville, Vt. 387 



inferred to be a metamorphosed eruptive of gabbroid, 

 diabasic, or basaltic character. 



Limestone. — The limestone (L, figs. 1 and 4) varies con- 

 siderably in texture, mineral content, and degree of meta- 

 morphism. It is quite subordinate to the gneisses as a 

 member of the country rock series. It crops out at four 

 localities about the main eruptive body and also about 

 one-half mile west of the area of breccia shown in fig. 4. 



The limestone on the southwest slope of Granite Hill 

 and on Mill River varies in color from bluish gray 

 through cream to white. It is fine-grained although the 

 sparkle of the calcite cleavage is distinctly visible. It 

 effervesces freely with dilute hydrochloric acid. Under 

 a hand lens grains of quartz and particles which are 

 probably graphite are noticeable. 



On the southwest slope of Copperas Hill (fig. 1) one or 

 more bands of crystalline limestone follow the easterly 

 to northeasterly strike and high dips of the enclos- 

 ing gneisses. One of the bands has an exposed 

 width of 20 feet. In working the pyrrhotite bodies which 

 replace the limestone along the belt of tinguaite dikes on 

 this slope of Copperas Hill (fig. 1) cuts have been made 

 in masses of limestone 5 to 15 feet thick associated with 

 hornblende gneiss. This limestone is light bluish gray to 

 white in color, fairly coarse-grained, and distinctly met- 

 amorphic. The metamorphism is presumably due to 

 regional rather than igneous contact action. Hand speci- 

 mens show, besides calcite, generally considerable musco- 

 vite or sericite, and more locally, abundant flakes of 

 graphite. Some bands carry much tremolite or wollas- 

 tonite developed in short prisms and fibers along the 

 planes of schistosity. All samples effervesce freely with 

 dilute hydrochloric acid. 



One half-mile southeast of the Granite Hill eruptive 

 a bed of coarsely crystalline tremolitic limestone about 

 15 feet thick is associated with quartzite and hornblende 

 and mica gneisses, and is cut by a dike of camptonite or 

 essexite-porphyry. 



The limestone indicated in fig. 4 varies from light gray 

 and medium-grained, with occasional graphite flakes, to 

 cream white and decidedly coarse-grained, with quartz 

 veins and considerable muscovite. There is a notable 

 amount of limestone altogether, although it soon passes 

 into sericitic schist. 



