NOTES  ON  THE  GOLD  VEINS  NEAR  GREAT  FALLS.  MARYLAND. 
By  Walter  Harvey  Weed. 
The  gold-bearing  quartz  veins  near  Washington,  D.  C,  have  beer 
known  for  many  years,  and  large  sums  of  money  have  from  time  tc 
time  been  expended  in  their  development.  A  full  account  of  the 
district  and  its  geologic  features,  by  Mr.  S.  F.  Emmons,  was  pub 
lished  some  years  ago.°  In  the  last  two  years  considerable  new  wort! 
has  been  done  at  the  Maryland  mine  and  extensive  prospecting  worli-j 
on  the  adjoining  Anderson  property.  As  the  results  are  interesting 
both  scientifically  and  economically,  a  few  notes  made  by  the  write!1 
are  presented  herewith. 
The  Maryland  mine. — This  property  is  developed  by  a  shaft  15< 
feet  deep,  with  levels  at  depths  of  100  and  150  feet.     On  thj  100-fooi 
level  the  vein  is  opened  up  for  100  feet  north  and  100  feet  south  o 
the  shaft.     The  vein  is  from  7  to  12  feet  Avide  and  consists  of  massive  \| 
coarsely  crystalline,  vitreous  quartz,  incased  in  Avell-defined  Avails  o 
mica-schist.     The  coarse  is  nearly  north-south  and  the  dip  85°  t 
the  Avest.     The  quartz  incloses  wedges  and  sliA^ers  of  the  schist,  bfl 
these  masses  of  schist  are  mostly  attached  to  the  Avails  at  some  poin  J 
though  apparently  isolated  masses  Avere  seen. 
Both  country  rock  and  vein  quartz  are  traversed  by  well-definec 
joints,  Avhich  form  an  angle  of  90°  with  the  plane  of  the  vein.  TheH 
fractures,  however,  in  the  instances  seen,  are  not  directly  continuoi  ■ 
from  country  rock  into  vein,  as  there  is  a  little  jog  where  they  pa* 
into  the  quartz.  This  fracturing  has  produced  slight  shifting  of  trJ 
veins,  and  combined  with  the  sheeting  of  the  vein  itself  giATes  a  nette 
or  diamond-meshed  structure.  The  course  of  the  veins  does  not  co 
respond  exactly  to  the  foliation  of  the  schist,  but  cuts  across  it  at 
slight  angle.  The  quartz  sIioavs  distinct  banding,  with  lines  mark* 
by  micaceous  material  and  pyrite.  Pyrite  occurs  abundantly  i 
isolated  cubes  in  the  quartz,  frequently  associated  with  galena.  Pyri 
also  occurs  in  small  crystals  in  the  included  masses  of  schist  and  in  tl  < 
schist  Avails,  but  is  pale  in  color  and  differs  in  appearance  from  tl  < 
quartz.  The  richest  ore  occurs  in  masses  varying  from  an  inch 
several  inches  in  diameter  and  is  formed  of  galena  with  coarse  fr 
a  Notes  on  gold  deposits  of  Montgomery  County,   Md.  :  Am.   Inst.   Min.   Eng.,   vol.  ' 
1890,  pp.  391-411. 
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