THE HAWLEY SCHIST. 



1()9 



up to the Davis mine, where, a niih- helow thu mine, a crossroa.l turns ..tl' 

 to the east. It has bhie (luartz, single twiuned feklspars, and very little 

 biotite, and is 60 I'eet thick. 



THE POSSIBLE IGNEOUS OKIGIN OF THE HAWLEY SCHIST. 



The theory that a ferromagnesiau formation like the present may be 

 in whole or part of igneous origin is very attractive, and I know of no sed- 

 imentary series which could be more easily transformed by wholly mtelli- 

 o-ible metamorphic processes into the present one than the Trias.sic beds of 

 the Holyoke range, with their interi^edded traps, tuffs, and lemigmous 

 sandstones, to which respectively the amphibolites, chloritic schists, and fas- 

 ciculate sericite-sclusts can be compared. There remains now no distmc- 

 tively eruptive structure in 

 these beds. The pseudo-por- 

 phyritic character of the am- n. 

 phibolites proves to be caused 

 by the exchision fi'om the 

 white spots of the black horn- 

 blende needles by a second- 

 aiy feldspar growth, now 

 more or less saussuritic, so 

 that the white feldspar ground 

 appears. A single very strik- 

 in. occurrence, looking like a small dike branclnng across the beddmg 

 occurs in Charlemont (fig. 9), going up over the W rocks wes o 

 A P Maxwell's (now Vincent's), a mile north of the vdlage, to the highest 

 rocky bluff visible in the woods from the house. On the east is the 

 common soft ankerite-chlorite-schist (a), and a sharp boundary hue sepa- 

 rates this from a white feldspathic muscovite-schist or gneiss of sandy 

 texture (h) Distinct dikes (c) of aid.erite-chlorite-schist of slightly dit- 

 ferent texture from the country rock («) appear in the latter and run out 

 into the white gneiss, branching and expanding into irregular forms. The 

 country rock is distinctly faulted by the dike, and a later fault cuts across 

 the whole and throws it, and this is filled with vein quartz (d) There is a 

 distinct foliation in the dike, which is in part parallel to that of the country 

 rock and in part divergent therefrom, as indicated in the figure. 



Fio 9.-Plan of altered dikes and quartz veins in chlonte-sclnst, 

 CUarlemont. a. ankerite-chlorite-schist; b, sandy muscoy.te-gneiss; 

 <■, altered dikes, now green ankerite-chlorite-schist; <(, blue-tiuart?, 

 veins. 



