196  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1906,  PART    I. 
Guernsey  formations  are  in  fault  contact,  the  amount  of  displacement 
being  over  200  feet,  with  the  downthrown  side  on  the  south.  Breccia- 
tion  has  accompanied  both  faulting  and  folding,  and  the  main  ore 
deposits  are  intimately  associated  with  it.  There  is  evidence  also  that 
in  some  places  the  schist  was  opened  along  its  planes  of  schistosity 
during  the  folding. 
The  Carbon  if erous  formations  occur  usually  as  flat-lying  remnants 
capping  the  pre-Cambrian  hill.  On  the  borders  of  the  uplift,  how- 
ever, the  Carboniferous  formations  at  many  places  dip  rather  steeply 
beneath  younger  formations. 
ORE   BODIES. 
FORM    AND    PLACE    OF   THE    ORES. 
The  most  important  iron-ore  deposits  of  the  Hartville  iron  range  are 
lenses  that  occur  in  schist  on  a  limestone  foot  wall.  The  ore  largely 
replaces  the  schist,  although  it  partially  (ills  cavities  in  the  schist 
which  are  due  to  jointing,  faulting,  and  brecciation.  Detrital  ores  of 
secondary  derivation  from  these  deposits  are  situated  (1)  at  the  base 
of  the  Guernsey  formation,  (2)  at  the  base  of  the  Hartville  formation, 
and  (3)  in  the  Tertiary  lake  and  Pleistocene  and  Recent  stream  depos- 
its. The  pre-Cambrian  jaspers,  an  amphibolitized  phase  of  the  schist, 
and  the  matrix  of  some  of  the  conglomeratic  facies  of  the  second  pre- 
Cambrian  series,  also  locally  contain  considerable  iron. 
The  most  important  ore  deposits  next  to  the  lenses  above  the  con- 
tact of  the  pre-Cambrian  schisl  and  limestone  are  situated  along  the 
fault  already  mentioned,  north  of  Guernsey,  between  the  pre-Cam- 
brian series  and  the  Guernsey  formation.  Although  but  little  devel- 
oped, these  deposits  will  perhaps  repay  careful  prospecting.  Masses 
of  hematite  and  limonitc  in  the  Haystack  Mountains  are  evidently 
the  iron  hats  or  gossans  of  sulphide  deposits  and  are  economically 
important. 
LENSES    OF    IRON    ORE    IN    SCHIST    UPON    A    LIMESTONE    FOOT    WALL. 
GENERAL  CHARACTER. 
The  principal  bodies  are  irregular  lenses,  elongated  parallel  to  the 
strike  of  the  metamorphic  sedimentary  rocks  in  which  they  occur. 
Their  range  in  width  is  from  a  few  to  100  feet  or  more,  and  some  of 
them  are  over  1,000  feet  long.  It  is  reported  that  one  ore  body  in  the 
district  has  been  proved  to  a  depth  of  900  feet.  The  principal 
deposits  of  this  type  include  those  of  the  Sunrise  mine  and  its  practi- 
cal extension1— the  Lone  Jack — and  the  Chicago  and  the  Good  Fortune 
mines.  Similar  ore  masses  occur  at  a  number  of  points  between 
these  ore  bodies. 
