peed.]  GOLD    VEINS    NEAR    GREAT    FALLS,    MARYLAND.  129 
jfold.  Sheeting  of  the  vein  after  deposition  of  these  minerals  has 
Produced  a  gilding  of  certain  surfaces  or  a  clouding  clue  to  galena 
lust.  The  pyrite  crystals  have  also  been  broken  by  an  earlier  period 
)f  fracturing,  and  the  fragments  have  been  recemented  by  quartz, 
rhe  quartz,  though  massive,  shows  plainly  the  outlines  of  hexagonal 
crystals  and  is  certainly,  in  part  at  least,  of  comb  structure.  The 
ichist  fragments  near  the  gold-bearing  nests  are  honeycombed  in  part 
md  the  cavities  drusy,  as  if  the  quartz  and  mica  were  being  dissolved. 
■50  far  as  can  be  determined  with  the  hand  glass,  the  ferromagnesian 
ninerals  are  being  removed  or  leached  out  by  alkaline  waters,  and 
martz  deposited  in  their  place,  together  with  pyrite,  since  the  pyrite 
aibes  projecting  into  these  cavities  are  not  affected.  The  secondary 
fractures  traversing  the  quartz  pass  at  times  directly  through  the  rich 
)*alena  and  gold  masses,  but  there  is  no  visible  connection  between 
he  fractures  and  the  nests  of  rich  ore.  At  the  same  time  there  is  an 
evident  association  of  the  gold  with  fractures  in  the  quartz,  though 
lot  as  a  filling  between  growing  crystals. 
Samples  of  the  solid  pyrite  from  the  100-foot  level,  showing  no 
risible  gold,  assayed  by  E.  T.  Allen  in  the  Survey  laboratory,  yielded 
L25  ounces  gold  and  0.36  ounces  silver  per  ton.     In  the  operation  of 
he  mill  a  considerable  tonnage  of  the  pyritic  ore  was  run  over  the  con- 
centrators.    The  resulting  product,  consisting  of  almost  pure  pyrite, 
yielded  upon  assay,  by  A.  C.  Kombauer,  of  Butte,  Mont.,  0.74  ounces 
lor  $14.80)  gold  and  1.5  ounces  per  ton  of  silver.     In  December  504 
ons  of  ore  from  the  pay  shoot,  run  through  the  mill,  yielded  $5,144. 
The  Anderson  projierty. — West  of  the  Maryland  mine  several  veins 
Lave  been  prospected  in  the  past  year  on  what  is  known  as  the  Ander- 
on  property,  Avhere  seven   veins  have  been  opened.     The  Potomac 
ein  crosses  the  Aqueduct  road  about  200  yards  east  of  the  canal  and 
5  at  this  point  exposed  by  two  adits.     The  north  adit  follows  the 
ein  for  135  feet,  the  course  var}'ing  from  N.  5°  E.  at  the  mouth  to 
18°  E.  near  the  face.     This  vein  has  a  dip  of  75°  to  80°  to  the  west, 
ad  for  this  distance  will  average  nearly  2  feet  in  width.     It  is  always 
istinct  and  well  defined,  but  thins  and  thickens  from  point  to  point. 
'he  vein  consists  of  crushed  and  decomposed  ferruginous  schist,  is 
dually  defined  by  a  clay  selvage,  but  varies  in  appearance  and  char- 
ter.    Opposite  a  winze  sunk  on  the  vein  at  a  point  100  feet  from 
ie  entrance  to  the  adit,  the  vein  shows  but  5  inches  of  crushed,  dull, 
ive-drab  schist.     The  winze  is  about  12  feet  deep,  and  at  the  bot- 
m  the  vein  is  opened  for  about  15  feet  in  length.     At  this  point, 
jmost  directly  opposite  the  5-inch  place  just  noted,  the  vein  is  3  to  5 
et  wide. 
The  exposures  in  the  Potomac  tunnel  show,  better  than  anywhere 
fee  in  the  property,  that  the  veins  cut  obliquely  across  the  schists 
|  dip  and  strike.     This  is  seen  40  feet  in  from  the  tunnel  mouth, 
Bull.  2C0— 05  m 9 
