358  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1906,  PAET    T. 
Eighty-eight    quarries   were  visited.     The   granite   of  nearly  all  ofj 
these  quarries  differs  from  that  of  those  in  Maine,  and  some  of  the 
geological  features  of  the  quarries  are  also  different.     These  granites 
differ  also  greatly  among  themselves,  as  may  be  seen  by  noting  the 
various  kinds  produced.     Among  these  are  the  fine-grained  Westerly] 
granites,  so  well  adapted  to  the  most  delicate  sculpture,  and  the  .Mil- 
ford,  N.  H.,  and  Chester,  Mass.,  granites,  which  somewhat  resemble! 
them;  the  dark   hornblende-augite  monumental  granite  of  Quincyl 
Mass.,  noted  for  its  high  polish;  the  massive  structural  granite  of  Mil- 
ford,  Mass.,  which  is  going  into  several  important  public  structures;' 
the  medium-grained  light-gray  muscovite  granite  of  Concord,  N.  H.J 
used  in  the  Congressional  Library  at   Washington;  the  olive-colored 
granites  of  Kockport.  Mass.,  and  Redstone,  N.  II.;  the  pink  granite 
of  Red-tone  X.  II..  and  the  mottled  medium-gray  granite  of  Rock- 
port,  Mass. 
In  describing  these  -tones  polished  specimens  of  one  or  two  typical 
granites  from  each  distrid  will  be  examined  l>v  the  Rosiwal  method, 
and  the  estimated  percentages  of  the  chief  mineral  constituents  will 
be  given  in  connection  with  the  microscopic  descriptions.  Some  of 
these  estimates  have  already  been  completed,  and  are  presented 
below  in  advance. 
The  "extra  dark"  hornblende-augite  granite  of  the  J.  S.  Swingle 
quarry  al  West  Quincy,  Mass.,  shows  feldspar,  56;  hornblende-augite, 
L0.50;  smoky  quartz,  33.50. 
The  "dark"  granite  of  the  Granite  Railway  Company's  quarry  at 
the  same  place  -how-  Feldspar,  58.79;  hornblende-augite,  7.47; 
smoky  quartz,  33.7  l . 
The  "dark"  granite  of  the  Maguire  &  O'Heron  quarry  at  Milton, 
aear  Quincy,  shows  feldspar,  55.80;  hornblende-augite,  I  1.10;  smoky 
quartz,  33.10. 
The  "medium"  granite  of  the  Wigwam  quarry  of  Badger  Brothers 
at  Wesl  Quincy  -how-  feldspar,  69.51;  hornblende-augite,  8.43; 
smoky  quartz,  22.06. 
These  results  indicate  thai  the  difference  in  the  shade  of  Quincy 
granite-,  designated  commercially  by  "medium,"  "dark,"  and 
"extra  dark,"  is  due  partly  to  differences  in  the  percentage  of  the 
hornblende-augite  and  partly  to  differences  in  that  of  the  smoky 
quartz. 
The  medium  gray  granite  from  the  Pigeon  Hill  quarry  (Lower 
quarry)  of  the  Pigeon  Hill  Granite  Company  at  Kockport,  on  Cape 
Ann,  Mass.,  show-  feldspar,  58.86;  hornblende,  7.2(i;  smoky  quartz, 
33.88. 
In  examining  the  fine-grained  granites  the  Rosiwal  method  is 
applied  to  camera  lucida  drawings  made  from  thin  sections,  with  an 
enlargement,  in  the  finest  ones,  of  40  diameters.     The  finest  of  the 
