smith]  QUARTZ    VEINS    IN    MAINE    AND    VERMONT.  83 
this  same  vein.  Here  it  is  even  more  irregular  in  width.  A  seam  of 
pyrite  one-half  inch  in  width  was  exposed  in  the  working  face  of  the 
tunnel  when  visited  in  July,  1903. 
Several  smaller  veins  have  been  located  on  the  same  slope  of  Mount 
Glines,  but  these  are  not  worked.  The  No.  6  vein  is  being  devel- 
oped by  a  shaft.  This  vein  is  similar  in  composition  to  No.  1,  and 
a  thickness  of  over  6  feet  is  exposed.  It  strikes  N.  20°  E.  and  is 
nearly  vertical,  dipping  to  the  north.  The  walls  of  this  vein  are  not 
so  sharply  denned  as  those  of  the  other  vein,  being  in  part  due  to 
approximately  parallel  shear  planes  developed  in  the  granite  walls. 
The  ore  minerals  are  galena  and  pyrite,  occurring  both  in  bunches 
and  in  a  fairly  distinct  streak,  4  inches  wide,  near  the  northern  side 
of  the  vein.  This  band  of  sulphides  dips  to  the  northwest,  crossing 
the  vein  at  an  angle  of  about  45°,  and  this  dip  agrees  with  that  of 
veins  of  quartz  seen  in  other  parts  of  the  main  vein. 
Open  fissures  also  occur  in  the  vein,  and  all  of  these,  like  the  small 
veins  of  quartz  and  the  streak  of  sulphides,  cross  the  general  structure 
of  the  quartz  gangue,  which  is  nearly  vertical,  while  the  others  are 
characterized  by  the  northwest  dip.  These  relations  are  considered 
as  evidence  of  a  Assuring  subsequent  to  the  formation  of  the  large 
fissure  and  the  crystallization  within  it  of  the  gangue  minerals.  The 
conclusion  suggested  by  this  hypothesis  is  that  the  ore-bearing  solu- 
tions were  of  later  origin  than  the  solutions  from  which  the  major 
portion  of  the  quartz  was  deposited.  This  assignment  of  a  later  date 
bo  the  ore  minerals  than  to  the  most  of  the  quartz  gangue  is  important, 
bince  it  follows  from  the  application  of  this  hypothesis  that  in  this 
region  thick  veins  of  quartz  are  not  of  themselves  necessarily  indica- 
tive of  the  presence  of  ore  unless  they  show  evidence  of  the  later 
fracturing  that  preceded  the  introduction  of  the  ore  minerals. 
The  ore  exposed  by  the  development  work  on  Mount  Glines  is  very 
irregularly  distributed  within  the  veins.  This  lack  of  natural  concen- 
tration detracts  from  the  value  of  the  ore.  Any  estimate  of  its  value 
ihould  not  disregard  the  proportions  in  which  the  metallic  sulphides 
ire  mixed  with  the  gangue  minerals.  Usually  the  nature  of  this 
J  admixture  is  such  that  the  greater  part  of  the  quartz  would  need  to  be 
landled  with  the  ore  minerals.  An  assay  of  anything  less  than  a  com- 
olete  sample  taken  across  the  entire  width  of  the  vein  therefore  would 
iave  little  direct  bearing  upon  the  economic  value  of  these  veins. 
Assays  from  the  Mount  Glines  property  have  been  reported  as  indi- 
cating values  ranging  from  $7.50  to  $49.68  per  ton,  it  being  stated 
hat  the  ore  increases  in  value  with  depth.  These  assays  were  doubt- 
t  iss  made  of  picked  material.  At  the  time  of  the  visit  to  this  prop- 
erty, No.  1  shaft,  which  had  been  sunk  to  a  depth  of  35  feet,  was  half 
all  of  water.  A  sample  was,  however,  collected  in  the  upper  part 
f  the  shaft,  where  the  vein  is  ^  feet  in  width.     This  sample  was  of 
