90  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1905. 
are  recovered  on  the  plates  in  the  amalgamation,  which  here  is  the  preliminary  process. 
A  considerable  amount  of  argentite  is  present  in  finely  divided  form,  and  panning  also 
yields  a  little  fine  gold. 
The  ore  shoots  of  the  Annie  Laurie  vein  have  an  ill-defined  lenticular  form  when  pro- 
jected on  the  plane  of  the  vein,  and  appear  to  pitch  45°  or  less  to  the  north.  Some  of 
them  at  least  have  cores  consisting  of  bunches  of  rich  ore,  gradually  decreasing  in  tenor 
toward  the  outside.     On  No.  3  level  in  the  shoot  the  vein  is  in  places  23  feet  wide. 
Conclusions. — The  ore  deposits  of  the  Gold  Mountain  district  possess,  in  some  of  their 
aspects,  more  than  local  interest.  We  find  here  in  the  plateau  country  of  southern  Utah 
an  isolated  volcanic  eruption  of  rhyolite  of  middle  Tertiary  age,  the  central  points  of  which 
now  form  some  of  the  highest  peaks  of  the  State.  Over  wide  areas  around  these  peaks 
extend  broad  plateaus  of  tutTs — all  of  them  barren  of  mineral  deposits*  The  ore  deposits 
are  found  in  the  focus  of  igneous  activity.  On  the  north  side  of  the  peaks  lies  the  Gold 
Mountain  district  of  quartzose  gold-silver  ores.  On  the  southeast  side,  near  Marysvale, 
where  the  core  has  been  deeply  trenched  by  Sevier  River,  are  the  old  mining  districts  of 
Ohio  and  Mount  Baldy,  in  which  there  is  but  little  activity  at  the  present  time. a 
The  Annie  Laurie,  as  to  country  rock,  ore,  and  structure,  is  an  almost  exact  counterpart 
of  the  Waihi  deposits  in  New  Zealand,  though  it  does  not  possess  the  great  number  of  veins 
nor  the  enormous  amount  of  ore  exhibited  by  the  latter  bonanza.  In  many  respects  it  is 
also  similar  to  the  De  Lamar  deposits  of  Idaho. 
These  veins  are  believed  to  have  been  deposited  by  hot  springs  in  fissures  as  a  last  phase 
of  volcanic  activity  shortly  after  the  close  of  eruptions  and  not  far  below  the  actual  surface 
of  that  epoch. 
a  Most  of  the  Marysvale  deposits  arc  said  to  contain  lead,  zinc,  and  copper.  Selenide  of  mercury 
(tiemannite)  occurs  in  the  Lucky  Boy  and  other  mines  in  the  Baldy  district  and  during  1886  and  1887 
was  even  mined  on  a  commercial  scale.  In  this  connection  it  should  be  stated  that  mercury  in  some 
form  is  also  reported  to  occur  in  the  Gold  Mountain  mines. 
