emmons.]  CACTUS  COPPER  MINE,  UTAH.  247 
extend  to  a  considerable  depth,  and  would  seem  to  indicate  that  in 
spite  of  the  limited  rainfall  the  corrasion  of  the  gulch  had  kept 
pace  with  the  oxidation  of  the  ore.  The  disintegration  of  the  rock 
within  and  along  the  shattered  zone  has  evidently  facilitated  its 
wearing  away  and  probably  had  much  to  do  with  determining  the 
location  of  the  gulch. 
The  width  of  the  zone  of  faulting  varies  from  15  to  ?>0  feet,  as 
shown  by  the  underground  workings  of  the  mine,  which,  as  already 
stated,  have  reached  a  depth  of  GOO  feet,  longitudinal  drifts  with  fre- 
quent crosscuts  being  driven  along  the  zone  at  vertical  intervals  of 
100  feet.  The  rock  within  this  zone  is  shattered  rather  than  sheeted, 
though  some  sheeting  is  visible.  There  are  no  well-defined  and  con- 
tinuous walls,  but  rather  indefinite  boundaries  between  the  impreg- 
nated zone  and  barren  country  rock  are  afforded  by  frequent  slip 
planes.  At  certain  points  there  is  apparent  evidence  of  cross 
faulting.  In  the  upper  50  to  100  feet  there  is  the  appearance  of 
rounded  bowlders  of  country  rock  within  the  fault  zone,  which  has 
been  thought  to  indicate  an  open  fissure  into  which  they  had  fallen 
from  the  surface.  It  appears  more  probable,  however,  that  these  were 
originally  angular  fragments  in  the  shattered  zone  that  have  been 
rounded  by  the  disintegrating  action  of  surface  waters.  Where  most 
clearly  seen  the  pyritous  ore  bodies  sometimes  form  a  sort  of  cement 
to  these  rounded  fragments,  and  fill  cracks  and  interstices  in  the 
shattered  rock.  It  is  likewise  concentrated  in  irregular  patches,  in 
which  case  alone  is  massive  chalcopyrite  visible.  The  decomposed 
country  rock  in  the  midst  of  the  ore  zone  contains  abundant  sericite, 
and  a  black  mineral,  apparently  hornblende,  often  simulates  a  metallic 
pre,  and  sometimes  occurs  in  radiate  groups  of  prisms  of  strikingly 
fresh  appearance.     They  may  be  tourmaline. 
Conclusions. — The  deposits  are  evidently  the  impregnation  by 
pyritous  ore  of  a  strong  fault  zone,  and  the  structural  conditions  indi- 
cate that  this  fault  zone  may  be  a  northern  continuation — possibly  a 
branch — of  the  Horn  Silver  fault.  Its  direction  is  more  to  the  west- 
ward of  north  than  is  the  latter,  but  structural  faults  rarely  follow  an 
absolutely  straight  line,  and,  as  shown  by  the  topography,  the  south 
fork  of  Copper  Gulch  is  very  nearly  in  line  with  the  Horn  Silver 
fault.  Moreover,  at  the  east  base  of  the  saddle  at  the  head  of  this 
Pork  there  is  a  contact  of  lime  rocks  with  granite  that  has  the  appear- 
mce  of  a  fault  contact  and  is  quite  in  line  with  this  fault.  If  this 
issumption  proves  to  be  correct,  it  is  probable  that  the  fault  zone 
continues  farther  to  the  northwest,  across  the  gravel  slopes  at  the 
west  base  of  Golden  Horn  Peak,  and  a  further  extension  of  the  copper 
leposits  in  that  direction  might  naturally  be  looked  lor. 
