MOUNT GREYLOCK. 185 



granulite or fine grained gneiss. These do not seem to be confined to any 

 particular portion of the horizon, nor are they persistent where they do occur. 



The scams and lenses of quartz in the calcareous schist are calcareous, 

 and the rock itself is often calcareous where it looks least so, and vice versa. 

 In structure it shows the same peculiarities as the limestone and schist of 

 the lower horizons. 



No fossils have yet been found in this formation on Greylock, although 

 the rock in many places is sufficiently fine grained and not too metamor- 

 phic for their preservation. 



The only reason for the entire omission of this horizon from Emmons's 

 section seems to be that his section traversed the mountain in one of the few 

 places where there are no outcrops on the calcareous belts. 1 



The following is a summary of Mr. Wolff's report on these rocks. A 

 bluish gray, finely crystalline limestone composed of calcite grains and 

 quartz grains, with occasional flakes of muscovite and considerable pyrite 

 scattered through the calcite. 2 (Thus a specimen from locality 212 on Peck's 

 brook, about 2 miles south of the Bellowspipe.) Traversing the limestone 

 are thin beds of graphitic, pyritiferous quartzite composed of quartz, feldspar, 

 pyrite, graphite, and muscovite. (Thus locality 7(14 in the Notch about 

 three-quarters of a mile south of its highest point.) 



The calcareous schist is composed of large grains of calcite mixed 

 with stringers of muscovite and graphite containing inclusions of mica, 

 graphite, calcite, and quartz. Pyrite and small fragments of microcline also 

 occur in it. (Thus a specimen from locality 712 on the west side of Ragged 

 mountain near its south end.) 



The feldspathic quartzite so often associated with or replacing the cal- 

 careous schist of this horizon consists of an interlocking 1 aarareffate of "Tains 

 of quartz and feldspar with rare Hakes of muscovite, small crystals of rutile, 

 and specks of limonite (thus at locality 345 in the Notch, west of the center 

 of Ragged mountain); and the gneiss, which seems intimately related to the 

 above, is a mixture of quartz with a large amount of feldspar, twinned and 

 untwinned plagioclase, with occasional grains of microcline and muscovite 



1 See Emmons's American Geology, part 2, p. IS. "From the termination of the limestone [i. e., the 

 Stockbridge limestone] to the top of Greylock the talcose slate is uninterrupted." 



-Recent assays of a similar specimen of this horizon are said to have shown the pyrite to he aurif- 

 erous, but not sufficiently so to give the rock any metallurgical value. 



