80  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.         [bull.  260. 
productive  properties  exploited  during  the  earlier  history  of  the  State. 
The  history  of  Lake  City  begins  with  the  discovery  of  the  Ute  and 
Ulay  mines  on  August  27,  1871.  Among  the  mines  which  have  been 
productive  since  that  discovery  the  following  may  be  regarded  as  the 
most  important:  Ute  and  Ulay,  Ocean  Wave,  Hidden  Treasure, 
Golden  Fleece,  Black  Crook,  Lellie. 
ORE  DEPOSITS. 
The  ore  deposits  of  the  Lake  City  region  may  be  grouped  under  the 
single  head  of  fissure  veins.  They  are  capable  of  a  further  subdivi- 
sion into  (1)  silver-bearing  fissure  veins,  (2)  gold-bearing  fissure 
veins. 
SILVER-BEARING    FISSURE    VEINS. 
General  features. — The  series  of  veins  which  are  described  undei: 
this  heading  in  most  cases  carry  silver  and  lead.     Gold  is  generally 
absent  or  very  subordinate  in  amount.     At  a  few  mines  consider-; 
able  values  in  gold  occur  in  certain  parts  of  the  ore,  especially  ir 
the  deeper  portions  of  the  mines,  but  these  are  exceptional.     Th<i 
Black  Crook  mine  might  be  mentioned  as  one  of  them.     The  veins  art 
contained  in  fissures  in  the  country  rock  which  have  been  filled  witl 
ore  and  gangue  minerals.    The  fissures  are  frequently  vertical  or  di] 
at  a  high  angle,  very  few  of  them  showing  a  dip  less  than  60°.     On 
or  two  instances  occur  where  the  inclination  is  as  little  as  45°.     Th 
width  of  the  fissures  ranges  from  a  few  inches  to  upward  of  10  fee 
and  varies  very  much  in  different  portions  of  the  vein,  pinches  an< 
swells  being  a  characteristic  feature.     Generally  a  narrow  portion  o 
the  vein  alternates  both  vertically  and  horizontally  with  larger  masse 
and  there  are  formed  irregular,  tabular  shoots  of  ore  and  gangue  mate 
rial,  separated  from  one  another  by  pinches  in  which  the  two  walls  o 
the  fissure  are  frequently  in  contact.     No  prevailing  direction  of  or 
shoots  can  be  observed.     The  irregularity  in  the  width  of  the  vein  i 
undoubtedly  caused  by  the  deviations  of  the  original  fissure  from 
straight  course  before  the  displacement  occurred.     No  distinct  syj 
terns  of  fissures  can  be  determined,  as  the  strikes  vary  within  wid 
limits  even  in  those  localities  which  contain  the  largest  number  c 
veins.     Some  of  the  veins  correspond  closely  with  the  jointing  of  tr  | 
country  rock.     Others  are  entirely  at  variance  with  it,  showing  th| 
the  vein  formation  has  probably  preceded  the  jointing. 
In  detail  the  fissures  are  usually  of  composite  character,  la  vi  | 
masses  of  country  rock  being  frequently  included  within  the  wall 
In  some  cases  the  veins  have  almost  a  brecciated  character.  Tl  < 
hanging  wall  is  frequently  more  irregular  than  the  foot  wall,  f(  I 
lateral  fissures  often  intersect  the  vein  on  the  hanging-wall  sid  5 
In  the  Hidden  Treasure  and  Ute  mines  the  veins  are  singular] 
