hiving.]  OURAY    DISTRICT,   COLORADO.  61 
with  a  fine-grained  greenish  groundmass  closely  resembling  an  erup- 
tive rock.  This  is  a  consolidated  friction  breccia  formed  in  the 
fissure.  A  later  opening  of  the  fissure  furnished  the  cavities  in  which 
the  ore  was  deposited. 
This  breccia  is  usually  3  or  4  feet  wide,  but  varies  greatly  in  width 
and  often  makes  out  in  excessively  small  stringers  into  the  wall  rock, 
sometimes  showing  compact  stringers  only  one-sixteenth  of  an  inch 
in  width  which  are  yet  perfectly  solid  and  exhibit  all  of  the  clastic 
characters  of  the  wider  occurrences.  It  is  formed  so  largely  of  the 
clayey  and  aluminous  material  that  result  from  the  comminution  of 
the  shales  and  limestones  which  make  up  the  larger  part  of  the 
country  rocks  of  the  McElmo  group  that  it  may  originally  have  had 
the  correct  composition  for  a  natural  hydraulic  cement.  The  seep- 
age of  hot  mineralizing  waters  into  the  fissure  would  have  supplied 
the  necessary  moisture,  so  that  the  consolidation  was  perhaps  accom- 
plished more  by  virtue  of  the  chemical  composition  of  the  material 
than  by  a  high  degree  of  lateral  compression,  as  suggested  by  Ran- 
some. 
From  the  Bachelor  tunnel  the  vein  has  been  opened  for  more  than 
1,000  feet  to  the  east,  when  it  becomes  barren,  and  to  the  west 
through  the  workings  of  the  Wedge  and  Neodesha  mines  into  Un- 
compahgre  Canyon.  At  the  Wedge  shaft,  about  midway  of  its 
course,  it  divides,  both  branches  passing  across  Gold  Hill  and  emerg- 
ing in  the  cliffs  which  form  the  east  bank  of  the  Uncompahgre 
River.  The  tAvo  branches  are  separated  by  an  interval  of  about  200 
feet  in  this  outcrop.  The  northern  branch  is  worked  by  the  Neode- 
sha  mine  and  the  southern  presumably  by  the  Pony  Express, 
although  no  connection  has  yet  been  made.  The  eastern  portion  of 
the  vein  is  vertical,  and  likewise  that  portion  of  it  operated  by  the 
Neodesha  mine,  but  the  branch  that  extends  into  the  Pony  Express 
mine  is  reported  to  have  a  slight  dip  to  the  south.  The  trend  of  the 
vein  before  its  division  is  N.  83°  E.,  or  very  nearly  east  and  west. 
In  this  respect  it  follows  very  closely  all  the  other  fissures  which  out- 
crop in  the  region  about  the  Uncompahgre  River  and  Dexter  Creek. 
The  fissure,  as  well  as  the  ore  deposited  in  it,  was  formed  subse- 
quent to  the  solidification  of  the  breccia  or  so-called  "  dike,"  as  it 
breaks  across  from  one  side  of  it  to  the  other  or  is  entirely  included 
within  it.  A  faulting  on  the  vein  of  about  7  feet  may  be  observed, 
by  which  the  south  side  has  been  lowered.  This  faulting  is  observ- 
able only  along  certain  portions  of  the  vein.  It  must  have  been  fol- 
lowed by  other  lateral  movements  before  the  deposition  of  the  ore, 
as  the  slickensides  on  the  harder  rocks  which  form  the  walls  are 
invariably  horizontal. 
Subsequent  to  this  movement  bedding  faults  occurred  which  have 
