202  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.        [bull.  260. 
statement  is  presented  now  as  a  preliminary  report.  After  an  intro- 
ductory general  description,  the  principal  features  of  the  two  proper- 
ties which  have  shipped  ore  are  briefly  described,  and  some  of  the 
other  localities  from  which  these  minerals  have  been  reported  are 
mentioned. 
The  general  chemical  determination  of  the  rare  vanadium  minerals 
collected  by  the  writer  has  been  made  by  Dr.  W.  F.  Hillebrand,  of 
the  United  States  Geological  Survey.  For  information  regarding 
special  deposits,  the  writer  is  indebted  to  Prof.  J.  E.  Talma dge,  of  Salt- 
Lake  City;  Mr.  S.  T.  Lockwood,  of  Buffalo,  N.  Y. ;  Judge  W.  A. 
Warf,  of  Price,  Utah,  and  Mr.  Ira  R.  Browning,  of  Emery,  Utah, 
and  for  valuable  cooperation  in  field  work  to  Manager  James  H. 
Lofftus,  Richardson,  Utah. 
GENERAL  DESCRIPTION. 
The  known  deposits  of  uranium  and  vanadium  minerals  in  Utah 
occur  in  the  eastern  and  southeastern  portion  of  the  State  in  the 
margins  of  the  basin  of  the  Green,  Grand,  and  Colorado  rivers. 
This  area  is  a  geographic  and  geologic  unit.  The  gentle  southerly 
dip  of  the  east-west  Uinta  Range  gradually  gives  way  to  a  flat  dip, 
then  in  the  Book  Cliffs  and  the  region  immediately  south  to  a  slight 
northerly  dip,  and  thus  forms  the  Green  River  Basin.  On  its 
margins  the  underlying  beds  are  turned  up  by  the  laccolithic  intru-j 
sives  of  the  La  Sal  group  on  the  east,  the  Abajo  cluster  on  the  south- 
east, the  Henry  Mountains  on  the  southwest,  and  the  San  Rafael 
swell  on  the  west.  The  rare  minerals  appear  to  be  restricted  to 
Mesozoic  sediments  in  or  adjacent  to  these  intrusive  centers. 
The  Utah  deposits  thus  occur  in  the  same  general  geographic  prov 
ince  as  the  deposits  of  western  Colorado,  and  probably  in  an  equiva 
lent  series  of  rock  formations,  but  they  differ  in  important  mmeralog-  | 
ical  characteristics  and  in  certain  features  of  geological  occurrence. 
In  general  the  Colorado  deposits  occur  in  sandstone  of  Jurassic  age, 
principally  in  the  La  Plata  formation,  except  on  La  Sal  Creek,  where 
the  thin-bedded  sandstone  in  which  the  uraniferous  deposits  occur 
was  believed  to  be  the  next  overlying   formation   in  the  Jurassic, 
known  as  the  McElmo  formation.0     Stratigraphic  work  on  the  for- 
mations constituting  the  country  rock  of  the  Utah  deposits  could  not 
be  undertaken  during  the  limited  time  at  the  writer's  disposal.     It 
appears,  however,  by  general  correlation  from  previous  surveys  that 
the  Cretaceous,  Jurassic,  and  perhaps  upper  Carboniferous  of  the  Col- 
orado locality  extend  Avestward  to  the  Utah  localities,  with  the  same 
°  Hillebrand,  W.   F.,  and  Ransome,   F.   L.,   Oarnotite  and  associated  vanadiferous   min- 
erals in  western  Colorado  :  Am.  Jour.  Sci.„  4th  ser.,  vol.  10,  1900,  pp.  120-144. 
