HIGHLANDS    OF    NEW    JERSEY.  639 
or  less  complete  obliteration  of  the  bedding  planes  by  excessive  meta- 
morphism.  The  beds  of  magnetic  ore  occur  in  different  horizons  of 
the  middle  group,  but  never  in  the  highest  or  lowest.  In  this  same 
group  the  beds  of  crystalline  limestone  appear  generally  to  be  at  a 
slightly  higher  horizon  than  the  magnetite  beds.  The  highest  gneissic 
and  schistose  group  corresponds  wvy  well  in  character  with  the  Mont- 
alban  system  of  Hunt.  These  rocks  arc  like  those  of  Trenton  and 
Westchester  counties  in  New  York.  Among  the  eruptive  rocks  are 
placed  those  which  occur  in  dikes,  such  as  diorite,  diabase,  kersantite, 
and  porphyry. 
Britton,106  in  1888,  describes  as  occurring  in  the  Archean  of  New 
Jersey  an  organic  form,  apparently  alga1,  to  which  he  applies  the 
name  Archceophyton  newberryanum. 
Nason,107  in  1890,  describes  the  Archean  of  Xew  Jersey.  Here  are 
found  four  types  of  rock:  The  Mount  Hope  type,  a  foliated  mag- 
net it  ic  gneiss,  the  magnetite  sometimes  largely  replaced  by  horn- 
blende, with  little  mica  ;  the  Oxford  type,  foliated  hornblende  gneiss, 
magnetite  and  biotite  in  places  almost  wholly  replacing  the  horn- 
blende; the  Franklin  type,  a  less  foliated  biotite  gneiss;  and  the 
Montville  type,  white  or  crystalline  limestone.  The  Franklin  type 
differs  from  the  Mount  Hope  and  Oxford  types  in  that  the  quartz 
and  feldspar  are  usually  in  sharply  angular  grains,  which  contrast 
with  the  roundish  grains  of  these  minerals  in  the  first  t  wo  types.  The 
crystalline  limestone  is  placed  under  the  Archean  only  provisionally. 
As  there  are  apparently  many  reasons  why  it  should  be  considered 
of  more  recent  origin,  there  is  greater  reason  for  supposing  that  if  a 
part  of  it  proves  to  be  Archean  all  will  not.  This  rock  is  found  at 
Montville,  Wanaque,  Pequest  Furnace,  Jenny  Jump  Mountain.  Ox- 
ford Church  (now  Hazen),  and  Mendham.  No  actual  contacts  be- 
tween the  different  groups  have  been  found.  The  distribution  of  the 
various  types  is  described  in  detail.  Whether  the  gneisses  are  sedi- 
mentary or  eruptive  has  not  been  ascertained,  but  there  are  many 
localities  in  which  true  eruptive  granitic  rocks  inclose  within  their 
masses  fragments  of  the  adjacent  schistose  and  gneissic  rock-.  Also 
in  the  Archean  is  frequently  found  gabbro,  which  is  almost  certainly 
of  igneous  origin.  Occurrences  of  graphite  are  widely  separated  in 
the  Archean  rocks.  At  one  place,  commencing  at  the  old  graphite 
mine  near  South  Bridge,  ii  is  found  continuously  for  35  miles.  A 
similar  rock  has  been  found  at  Iona  Island  in  Hudson  River,  35  miles 
northeast.  Another  Line  is  found  on  Bald  Hill,  and  a  third  graphite 
gneiss  is  found  on  a  hill  east  of  Pompton  station  and  in  part  of  the 
Kamapo  Mountain  range.     Graphite  occurs  at  other  places,  also. 
NTason,108  in  L891,  describes  the  relations  of  the  white  and  blue 
limestones  of  Sussex  County,  X.  J.  They  are  found  to  grade  into 
each  other  at  many  points.    The  white  limestone  is  always  associate 
