198  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1905. 
western  and  central  hills.  Solution  cavities  here  are  almost  certain  evidence  that  watenj 
heated  by  the  trachyte,  similar  to  those  now  coming  from  it  on  the  south  side  of  the  gulcl 
and  in  one  spring  depositing  limonite,  were  the  agents  of  the  all  era!  ion. 
The  limonite  and  other  alteration  products  of  the  iron  carbonate,  together  with  the  resid- 
ual magnetite  and  hematite  whi<  h  were  originally  associated  with  it,  constitute  the  ores  of 
this  area.  The  principal  showing  of  ore  is  on  the  east  end  of  the  western  hill.  Here  several 
drifts  have  been  run  into  the  hill.  The  ere  may  be  seen  to  extend  along  the  hill  for  500  or 
more  feet,  and  into  the  hid  horizontally  for  CO  feet.  The  ore  consists  of  nodules  and  irreg- 
ular masses  of  limonite,  magnetite,  and  hematite  lying  in  an  iron-stained  matrix  of  clay 
and  (ariying  abundant  secondary  chlorite  or  talc,  li  is  much  broken  and  contorted. 
Beneath  the  surface  the  harder  nodules  disappear  and  the  ore  is  principally  soft  limonite 
or  hematite,  w  i  h  <  !a\  and  some  magnet  i.e.  The  best  of  the  ore  is  said  to  run  55  or  60  per 
cent  metallic  iron,  but  the  average  published  by  Birkinbine  is  35  per  cent,  Several  pull 
lished  analyses  show  phosphorus  below  the  Bessemer  limit,  but  much  of  the  ore  is  said  to 
run  higher.     Sulphur  is  low  in  boh  the  main  body  of  the  ore  and  (he  oxidized  portion. 
On  the  central  iron-carbonate  hill  several  tunnels  have  been  driven  into  the  hill  to  a  dis- 
tance of  100  or  more  feet.      The  oxidation  of  tin1  iron  carbonate  may  he  seen  to  extend  but  i 
a  few  feet  into  the  hill. 
In  two  localities  titaniferous  magnetite  was  observed.  One  is  to  the  northeast  of  the 
centra]  hill,  between  this  hill  and  the  trachyte,  where  il  is  shown  in  a  pit  associated  with 
an  altered  greenish  rock  now  represented  only  by  large  mica  plates  and  some  feldspar  in  a 
clayey  matrix.  The  other  locality  i-  across  the  creek  from  the  springs  just  east  of  the 
bridges  where  there1  is  a  bell  fully  50  feet  wide  apparently  running  up  the  slope  for  100  feet 
or  more.  This  has  been  opened  ai  one  place.  One  specimen  taken  here  showed  42.71  per 
cent  iron,  0.002  per  cenl  phosphorus,  0.00'.)  per  cent  sulphur,  and  4.15  per  cent  titanic  acid. 
No  associated  rocks  are  visible,  but  the  magnetite  contains  narrow  bands  of  greenish 
amphibole,  partb  altered  to  asbestos.  It  may  be  that  the  associated  rock  is  the  basic 
granite  to  be  seen  in  the  creek  bottom  beneath  the  bridge. 
CALIFORNIA. 
A  visit  was  made  to  the  Cave  Canyon  iron  area,  about  one-fourth  of  a  mile  north  of  Scott' 
station,  on  the  San  Pedro  Railroad  (Cave  Canyon  mines).  It  lies  on  the  south  side  of  the 
hills,  between  a  complex  of  acid  and  intermediate  rocks  on  the  north  and  coarsely  crystal- 
line marble  on  the  south,  dipping  southward  at  about  30°.  The  iron  is  mainly  along  the 
contact,  but  apparently  projects  into  the  igneous  complex  below  and  into  the  marble  above. 
Little  patches  of  marble  were  -ecu  in  what  was  taken  to  be  iron  ore.  The  exposure  is- 
much  broken  and  covered  by  desert  varnish,  with  the  result  that  the  surface  distribution 
is  not  at  once  obvious.  While  the  iron-ore  debris  covers  the  slope,  in  several  places  the 
igneous  rocks  appear  through  it.  The  ore  occurs  in  two  belts,  one  along  the  trend  of  the 
other,  but  separated  by  an  erosion  valley.  The  western  belt  is  about  2,000  feet  long  and 
the  eastern  1,700  fvvt  long.  The  width  of  outcrop  reaches  a  maximum  of  450  feet.  Its 
average  width  for  the  v.  es  era  belt  may  be  300  feet  and  for  the  eastern  belt  100  feet.  The 
true  thickness  of  the  ore  body,  assuming  that  it  follows  approximately  the  contact  of  the 
limestone,  is  probably  less  than  half  the  width  of  outcrop  because  of  the  southward  dip  of 
the  formation  and  the  fact  thai  1  he  erosion  slope  follows  the  dip.  Four  tunnels  are  reported 
on  the  property.  Two  were  seen  in  ore,  i  he  longer  one  30  feel  in  lengi  h.  The  ore  is  mainly 
red  hematite  and  limonite,  soft  and  broken,  showing  limestone  bedding.  In  one  of  the 
western  tunnels  green  iron  silicates  were  observed  in  the  ore.  The  ore  was  not  sampled. 
Commercial  analyses  from  two  sources  show-  a  percentage  of  iron  above  00  per  cent  and 
phosphorus  within  the  Bessemer  limit. 
