198  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.        [bull.*2G0. 
American  Molybdenum  Company.  At  the  mine,  however,  the  writer] 
was  not  permitted  to  examine  the  property  thoroughly.  A  shaft 
has  been  sunk  and  some  drifts  are  said  to  have  been  run  on  the 
molybdenite  ore,  but  the  secretive  policy  of  the  management  pre- 
vented any  observations  which  would  furnish  a  basis  for  a  statement 
of  the  probable  extent  of  the  deposit.  Observations  made  at  the 
surface,  however^  furnish  data  for  a  consideration  of  the  character 
and  origin  of  the  deposit. 
The  molybdenite  occurs  both  in  pegmatite  dikes  and  in  the  granitJ 
cut  by  these  dikes.  A  number  of  distinct  pegmatite  dikes  were  seen 
on  this  property,  varying  in  width  from  a  few  inches  to  several  feet. 
In  these  the  molybdenite  occurs  in  lead-gray  hexagonal  crystals  of 
short  prismatic  habit,  or  as  less  regular  foliated  masses,  often  with 
radiate  structure.  These  crystals  and  bunches  of  molybdenite  range 
from  1  to  2  inches  in  diameter  and  are  intimately  mixed  with  the 
quartz  and  feldspar  of  the  pegmatite.  The  molybdenite  is  possibly 
more  abundant  near  the  contact  with  the  country  rock,  yet  there  il 
no  parallel  arrangement  of  the  minerals,  but  rather  the  intergrowth 
characteristic  of  pegmatites.  The  molybdenite  is  the  only  con- 
stituent of  the  pegmatite  possessing  well  defined  crystal  faces,  except 
in  places  where  the  feldspar  crystals  project  into  open  spaces. 
The  molybdenite  occurs  also  in  small  flakes  or  larger  nests  of 
flakes  disseminated  throughout  the  granite  mass.  The  granite  il 
other  respects  is  the  light-gray  fine-grained  variety  common  to  thl 
region  and  is  probably  of  late  Paleozoic  age.  It  is  comparatively 
poor  in  the  darker  minerals,  but  in  places  near  the  pegmatite  dikes 
the  flakes  of  molybdenite  are  sufficiently  abundant  to  give  the  rock 
the  appearance  of  a  granite  rich  in  biotite. 
Molybdenite  occurs  at  several  other  localities  in  Maine  as  well  as 
in  the  other  New  England  States.     It  is  usually  found  in  small  flakes 
disseminated  through  the  granite  or  gneiss,  so  that  the  Cooper  occur-r 
rence  is  of  special  interest  by  reason  of  the  light  it  throws  on  th( 
origin  of  this  mineral.     The  pegmatite  dikes  are  probably  approxii 
mately    contemporaneous   with    the   granite    intrusion,    representing 
the  latest  crystallization  of  the  granitic  magma  and  therefore  intrud 
ing  the  consolidated  granite.     In  this  pegmatite  magma  molybdenun 
disulphide   appears  to  have   been   a   prominent   constituent,   and   t< 
have    crystallized    early    in    the    consolidation    of   the   dikes.      Th" 
molybdenite  in  the  granite  may  be  either  the  result  of  impregnatioi 
at  the  time  of  the  pegmatitic  intrusion  or  an  original  constituent 
The  former  view  is  supported  by  the  apparently  greater  amount  il 
the  granite  near  the  dikes. 
The  economic  value  of  such  a  deposit  as  the  Cooper  molybdenite 
is  partly   conjectural.     The   conditions   for  quarrying   and   minin  ; 
