HARTVILLE    IRON-ORE    RANGE,  WYOMING. 
193 
Colorado  Fuel  and  Iron  Company.  Since  that  time  this  company  has 
been  adding  to  its  holdings  and  now  controls  most  of  the  more  valu- 
able claims.  It  is  rapidly  developing  two  mines,  the  Sunrise  and 
Chicago,  which  now  furnish  the  greater  portion  of  the  ore  used  at  its 
smelters  at  Pueblo,  Colo. 
PRODUCTION. 
The  production  of  the  Hartville  iron  range  is  tabulated  below : 
Production  of  Hartville  iron  range,  1898-1906. 
Year. 
Mine. 
Quantity. 
1898-99 
Good  Fortune  mine 
Long  tons. 
30, 000 
1900 
73,  663 
1901 
do 
134, 161 
1902 
do 
209, 272 
214,  880 
135, 167 
1903 
.do 
1904 
do 
1905 
Sunrise  and  Chicago 
474, 545 
1900 
do 
In  1905  the  Sunrise  mine  was  in  point  of  production  the  twentieth 
iron  mine  in  the  United  States,  but  two  mines  outside  of  the  Lake 
Superior  region  exceeding  it  in  output.  The  product  of  the  range 
shows  an  encouraging  increase,  which  will  presumably  become  greater 
from  year  to  year. 
GEOLOGY. 
STRATIGRAPHY. 
The  rocks  of  the  Hartville  iron  range  fall  naturally  into  three 
groups:  (1)  The  steeply  dipping  pre-Cambrian  rocks,  (2)  the  flat- 
lying  or  gently  dipping  Carboniferous  and  Mesozoic  rocks,  and  (3)  the 
rocks  of  Tertiary  and  Recent  age  encircling  the  older  rocks  and  filling 
depressions  of  erosion  extending  up  into  them. 
The  pre-Cambrian  rocks  consist  of  metamorphosed  sedimentary 
rocks  and  of  igneous  rocks  and  their  mashed  equivalents.  The  oldest 
rocks  are  an  interbedded  series  of  siliceous  limestones,  probably  dolo- 
mitic,  and  muscovitic  and  biotitic  schists.  In  all  there  appear  to  be 
about  fifteen  beds  of  limestone  and  schist,  which  alternate  with  one 
another.  The  beds  vary  in  thickness  from  20  to  500  or  more  feet. 
The  schist  also  occurs  as  lenses  in  the  limestone,  these  lenses  grading 
both  parallel  to  and  across  their  longest  direction  into  rocks  that  are 
intermediate  in  composition  between  schist  and  limestone.  The 
limestone  is  typically  a  fine-grained  rock  of  pinkish  or  grayish  color 
and  has  a  conchoidal  fracture.  Lenses  and  beds  of  cream-colored 
flint  lie  parallel  to  the  original  planes  of  stratification  and  to  a  minor 
extent  cut  these,     The  schists  vary  in  color  from  silvery  to  very  dark 
