ADIRONDACK    MOUNTAINS.  605 
series  consisting  of  red  and  gray  orthoclase  gneisses,  usually  lam- 
inated, but  at  times  rather  massive.  In  these  gneisses  are  the  work- 
able iron  ores  of  the  Adirondacks.  (2)  Apparently  resting  on  1,  a 
series  of  crystalline  limestones,  ophicalcites,  black  hornblendic  py- 
roxenic  schists,  and  thinly  laminated  garnetiferous  gneiss.  Pegma- 
tite veins  are  a  frequent  associate  of  these  rocks.  (3)  A  series  of 
rocks  of  the  gabbro  family,  ranging  from  aggregates  of  labradorite 
through  varieties  with  increasing  amounts  of  bisilicates  to  basic  oli- 
vine gabbros.  The  gabbros  vary  from  massive  to  gneissoid  rocks 
which  are  difficult  to  discriminate  from  some  of  the  gneisses  of  series  1. 
These  rocks  contain  the  titaniferous  iron  ores.  They  are  intrusive  in 
series  1  and  2.  Resting  unconformably  upon  1,  2.  and  3  is  the  Pots- 
dam sandstone. 
Smyth  (C.  H.,  jr.),32  in  1895,  describes  the  crystalline  limestones 
and  associated  rocks  of  the  northwestern  Adirondack  region.  The 
limestones,  instead  of  being  in  limited  patches  as  in  the  eastern  part 
of  the  Adirondacks,  are  in  extended  belts  many  square  miles  in  area. 
The  limestone  belt  running  through  the  townships  of  Kossie  and 
(louverneur  has  been  traced  more  than  20  miles  along  the  strike, 
while  the  average  width  is  perhaps  6  miles.  A  narrower  belt  ex- 
tends across  Fowler  into  Edwards  Township.  A  third  belt  crosses 
the  townships  of  Diana  and  Pitcairn,  with  an  average  width  of  2  or 
3  miles.  In  addition  to  these  belts,  numerous  scattered  patches  have 
been  noted  in  the  western  Adirondacks. 
The  limestones  are  highly  crystalline,  coarse,  light-gray  or  white 
rocks,  containing  silicates  in  separate  crystals  or  segregated  in  lumps. 
Among  these  phlogopite,  graphite,  pyroxene,  and  tourmaline  are  most 
common.  The  limestone  is  usually  so  massive  that  it  is  difficult  to 
ascertain  the  strike  and  dip  with  any  accuracy.  When  observable  the 
strike  is  generally  northeast  and  the  dip  northwest,  though  exceptions 
are  common.  Garnetiferous  and  micaceous  gneisses  and  pyroxenic 
and  hornblendic  gneisses  are  intimately  associated  with  the  limestone. 
The  former  are  in  some  cases  distinctly  interbedded  with  the  limestone, 
while  many  of  (he  latter  have  the  appearance  of  interbedded  members, 
and  others  closely  resemble  somewhat  modified  intrusions.  Wherever 
the  hornblendic  and  pyroxenic  gneisses  appear  they  show  a  great 
amount  of  crumpling  and  crushing,  which  goes  from  slight  plication 
to  elaborate  contortion  or  to  crushing  into  angular  fragment-  in  a 
paste  of  limestone,  thus  producing  remarkable  breccias.  In  all  of 
these  cases  the  limestone  shows  little  or  no  sign  of  structural  change. 
having  the  appearance  of  a  plastic  mass  in  which  the  contained  layers 
could  be  twisted  to  any  extent.  It  therefore  follow-  (hat  the  massive 
and  undisturbed  appearance  of  the  limestone,  when  free  from  gneissic 
layers,  does  not  show  that  it  has  not  been  subjected  to  intense  mechan- 
ical strain,  as  subsequent  to  this  it  may  have  recrystallized. 
