leith]  IRON    ORES    IN    SOUTHERN    UTAH.  231 
tours  of  the  hills,  and  sometimes  rising-  as  much  as  100  feet  aoove  the 
base  of  the  outcrop.  Fragments  of  the  ore  have  fallen  down  the 
slopes,  giving  an  impression  that  the  ore  occupies  a  larger  area  than 
it  really  does.  In  width  the  outcrops  vary  from  a  few  inches  to  600  or 
more  feet,  and  have  the  shape  of  lenticular  veins.  In  general  the 
masses  of  ore,  in  following  the  contact  of  the  andesite  and  limestone, 
dip  toward  and  under  the  limestone,  though  markedly  so  in  but  few 
places,  as  in  certain  parts  of  the  Pinto  group  and  the  Desert  Mound, 
where  the  ores  are  found  to  extend  well  under  the  limestone.  At 
Desert  Mound  ore  apparently  occurs  not  only  at  the  contact  of  the 
andesite  and  limestone  but  within  the  limestone  itself,  although  fur- 
ther exploration  may  afford  some  other  explanation  of  the  occurrence 
in  this  locality.  Also  ore  may  be  observed  to  be  entirely  within  the 
andesite,  as  in  the  vicinity  of  the  Great  Western  mine  to  the  north  of 
Iron  Springs  and  above  the  Duluth  group  in  the  southern  part  of  the 
district,  and  in  the  Mountain  Lion  group  of  the  central  part  of  the 
district.  At  the  former  locality  several  roughly  parallel  lenticular 
veins  of  ore,  varying  in  thickness  from  a  f\ action  of  an  inch  to  20  feet 
or  more,  appear  in  the  andesite. 
The  contact  of  the  ore  and  limestone  may  be  observed  at  a  number 
of  localities,  and  especially  well  in  pits  in  the  Pinto  group  and  on 
Desert  Mound.  While  the  contact  is  well  defined,  in  detail  it  is  irregu- 
lar; small  stringers  and  projections,  and  also  apparently  isolated  masses 
of  ore,  appear  in  the  limestone.  The  limestone  is  much  altered  to 
clayey  material  and  is  stained  with  iron  oxide  at  the  contact.  At  one 
locality,  the  Homestead  mine,  the  limestone  is  largely  replaced  by  iron, 
although  the  rock  still  has  the  aspect  of  a  limestone.  An  analysis  by 
George  Steiger  is  as  follows: 
Analysis  of  ore  from  Homestead  mine,  Utah. 
Per  cent. 
Fe 57.32 
MgO 3.09 
CaO 3.09 
PA 29 
At  the  contact  of  the  ore  with  the  andesite,  the  andesite  commonly 
is  much  altered  and  consists,  for  many  feet  from  the  contact,  of  a 
clayey  mass  retaining  andesite  textures,  but  iron  stained  and  some- 
what brecciated. 
Nature  of  the  ore. — The  ore  appearing  in  the  jagged  exposures  is  a 
hard  black  crystallized  hematite  and  magnetite,  these  minerals  being 
present  in  varying  proportions.  The  hematite  tends  to  occur  in 
botryoidal  or  mammillary  forms  and  the  magnetite  in  coarse  octa- 
hedra,  often  with  modified  dodecahedral  faces.     Associated  with  the 
