126  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1905. 
In  Sinbads  Valley  massive  Carboniferous  limestones,  belonging  below  the  Permian  con- 
glomerates, are  exposed.  It  is  probable,  therefore,  that  considerable  thicknesses  of  both 
of  these  strata  would  be  crossed  before  the  basal  granite  was  reached. 
The  Dolores  formation  in  its  typical  development  of  red  sandy  shales  and  limestone  con- 
glomerates was  observed  just  south  of  the  bridge  crossing  Dolores  River  at  Paradox.  It  is 
the  base  of  the  section  as  there  exposed.  In  the  country  to  the  north  and  west  the  Cutler 
formation  (Permian)  underlies  the  Dolores  and  consists  of  a  great  thickness  of  red  sandstones 
and  conglomerates,  with  occasional  beds  of  red  shale  and  lenses  of  gypsum.  At  several 
places  the  Cutler  and  Dolores  are  separated  by  an  angular  unconformity,  showing  that  there 
was  tilting  and  erosion  between  the  periods  of  their  deposition,  but  in  Paradox  Valley  their 
dip  appears  to  be  uniform. 
The  La  Plata  formation  occupies  a  large  area  in  this  region  and  often  forms  the  "rim  rock" 
of  the  valleys.  The  later  formations  generally  occur  as  more  or  less  isolated  areas  on  the 
higher  portions  of  the  plateau.  In  Paradox  and  Sinbads  valleys  the  rocks  are  complexly 
dislocated  by  faults  of  considerable  throw  in  some  eases  several  hundred  feet.  A  pro- 
nounced fissure  trends  northward  from  Cashin  to  Paradox  Valley.  The  crushed  sandstone 
along  this  fissure  shows  that  it  has  been  a  plane  of  movement ,  though  the  beds  show  little 
displacement. 
There  are  no  igneous  rocks  in  the  immediate  vicinity  of  the  mine.  A  body  of  "porphyry'] 
is  reported  to  occur  6  miles  southwest  of  Cashin,  and  the  La  Sal  Mountains,  a  laceolithic 
group,  are  about  10  or  12  miles  to  the  west . 
To  judge  from  the  thickness  of  the  La  Plata  sandstone  above  the  mine,  the  tunnel  must 
enter  that  formation  near  its  base  and  the  Triassic  limestone  conglomerate,  if  present,  would 
appear  near  the  lower  workings.  Mr.  J.  X.  McBride  states  thai  the  ore  becomes  very  much 
richer  in  lime  in  that  portion  of  the  mine,  and  this  may  be  because  of  the  proximity  of  the 
limestone.  There  is  so  much  crushed  quartz,  kaolin,  and  secondary  calcite  at  this  point  that 
with  the  present  limited  development  here,  the  country  rock  could  not  be  determined  with 
certainty. 
ORE  DEPOSITS. 
The  ore  deposits  occur  along  a  fissure  which  cuts  the  La  Plata  sandstone.  The  dip  of  this 
fissure  is  75°  W.  and,  though  it  bends  slightly,  its  general  strike  is  about  N.  20°  E.  Accord- 
ingtoMr.  Thomas  L.  Darby,  the  fissure  may  be  traced  on  the  surface  northward  to  the  rim  of 
Paradox  Valley,  2  or  3  miles  distant,  but  the  writer  was  unable  to  examine  this  portion  of 
the  lode,  nor  to  observe  its  behavior  in  the  formations  above  the  La  Plata.  A  tunnel  with 
its  portal  about  30  feet  above  La  Sal  Creek  has  been  driven  northward  on  the  lode  for  700 
feet.  An  inclined  shaft  connecting  with  the  surface  and  extending  100  feet  below  the  level 
of  the  tunnel  crosses  it  about  halfway  to  the  breast,  thus  exposing  400  feel  of  beds.  In 
places  considerable  ground  above  the  tunnel  has  been  stoped  out  and  short  drifts  have 
been  run  on  the  vein  at  several  levels. 
The  nonmetallic  minerals  are  crushed  quartz  sand,  kaolin,  calcite,  barite,  and  vein  quartz. 
The  metallic  minerals  are  covellite,  chalcocite,  bornite,  native  copper,  malachite,  azurite, 
cuprite,  and  iron  sulphate.  Argcntitc  and  native  silver  occur  near  the  surface  in  pockets 
of  considerable  size,  but  at  the  time  of  visit  these  had  been  removed. 
The  lode  varies  in  width  from  1  foot  to  20  feet  or  more  and  is  composed  mainly  of  crushed 
sand  and  kaolin,  containing  small  specks  of  copper  sulphides.  It  is  often  stained  green  by 
copper  carbonate  and  iron  sulphate.  There  is  not  always  a  distinct  line  of  demarcation 
between  the  lode  and  the  wall  rock,  since  the  lode  is  made  up  largely  of  the  material  of  the 
country  rock,  altered  somewhat  by  movement  and  concomitant  processes.  The  green  dis- 
coloration sometimes  extends  beyond  the  fissure,  a  feature  which  is  strikingly  shown  on  the 
face  of  the  cliff  southwest  of  the  portal  of  the  tunnel. 
Rich  ore,  composed  largely  of  argentiferous  covellite,  chalcocite,  and  bornite  and  also  car- 
rying calcite  and  barite,  occurs  as  veinlets  in  the  (issure  zone.  These  verniers  arc  from  1  inch 
to  several  inches  wide  and  are  sometimes  composed  entirely  of  the  copper  sulphides,  the 
