vanhisb.]  LAKE    SUPERIOR    REGION.  99 
The  Quartzite  group  is  in  places  inter  stratified  with  ferruginous  and 
siliceous  seams,  as  well  as  novaculitic  strata  and  siliceous  limestones. 
Frequently  in  the  quartzite  is  a  conglomerate  containing  abundant 
quartz  fragments,  and  also  not  infrequently  containing  granite  and 
slate  fragments.  Oftentimes  these  conglomerates  containing  the  gran- 
ite fragments  are  very  close  to  the  massive  granite,  while  it  not  infre- 
quently underlies  them.  At  one  place  in  which  the  quartzite  is  in  con- 
tact with  the  granite  the  one  rock  is  seen  to  graduate  by  imperceptible 
stages  into  the  other,  in  which  case  the  sedimentary  strata  are  changed 
into  the  granite-like  rock  by  being  exposed  to  the  contact  with  the 
eruptive  granite.  In  another  place  a  granite  breccia  containing  large 
fragments  of  granite  is  found  in  connection  with  such  large  masses  of 
granite  as  to  be  too  great  to  be  fragments  of  a  breccia,  and  this  sug- 
gests that  the  nucleus  of  the  hills  are  solid  granites,  whose  shattered 
portions  are  recemented  on  the  spot  by  sedimentary  debris  washed 
into  the  interstices.  In  the  next  hill  to  the  south  the  inclosed  water- 
worn  pebbles  are  in  part  granite  and  in  part  slate.  Above  the  ore- 
bearing  rock  beds  is  generally  a  very  coarse  quartzite  conglomerate 
which  often  has  the  characters  of  a  coarse  grained  ferruginous  quartz- 
ite and  grades  down  into  a  brecciated  ore.  The  fragments  are  chiefly 
ore,  jasper  and  quartz,  and  the  cement  is  arenaceous  or  ferruginous. 
This  occurrence  is  so  general  as  to  suggest  that  great  disturbances  not 
of  a  local  extent  must  have  occurred  at  the  end  of  the  era  of  iron  sedi- 
ments. The  number  of  localities  and  mines  at  which  this  conglomerate 
or  breccia  occurs  is  very  great.  Among  the  latter  are  the  Home,  Gib- 
bon, Jackson,  Cleveland,  Cascade,  Gribben,  Salisbury,  Lake  Superior, 
Champion,  Saginaw  and  Goodrich,  Keystone,  Eepublic,  and  Michi- 
gamme. 
The  Iron  group  occupies  a  position  inferior  to  the  Quartzite  group, 
and  there  are  not  two  horizons  here,  as  supposed  by  Brooks.  It  is  com- 
posed of  banded  jasper,  conformable  chlorite- schist,  and  ore.  The  ore- 
deposits  are  not  regular  sedimentary  layers,  but  the  product  of  the 
decomposition  of  the  impure  ledges  by  percolating  waters,  leaching  out 
the  siliceous  matter  and  replacing  it  with  iron  oxide,  and  are  therefore 
very  irregular  in  form.  The  strata  are  in  a  much  disturbed  condition, 
folded  and  distorted  in  every  possible  way,  usually  without  fault. 
These  disturbed  beds  lie  in  every  instance  directly,  but  often  uncon- 
formably,  on  chloritic  or  hydromicaceous  schists,  or  on  crystalline  dio- 
ritic  masses,  which  are  constant  associates  of  the  chlorite  schists,  or  on 
dioritic  schists.  At  the  Jackson  mine  are  knobs  of  diorite  associated 
with  schists  surrounded  by  the  banded  jasper  rocks,  which  are  evi- 
dently corrugated  by  the  intrusion  of  this  mass.  In  places  the  ore- 
bearing  formation  is  not  found  incumbent  on  the  Dioritic  group.  At 
Teal  lake  the  quartzite  is  found  under  the  ore  and  the  diorite  over  the 
ore,  which  leads  to  the  conclusion  that  these  strata  are  in  an  over- 
turned position. 
