﻿204 
  REPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  

  

  Leaving 
  out 
  the 
  surface 
  specimen 
  from 
  tbe 
  Dry 
  Arroya 
  and 
  tlie 
  poor 
  

   specimens 
  from 
  Stephens 
  bank 
  (No. 
  9), 
  tbe 
  average 
  percentage 
  of 
  ash 
  

   in 
  the 
  Trinidad 
  coal 
  would 
  11.15 
  per 
  cent. 
  

  

  A 
  total 
  average 
  taken 
  of 
  the 
  Colorado 
  coal, 
  excluding 
  the 
  anthracite 
  

   varieties 
  from 
  the 
  Gunnison 
  and 
  the 
  Elk 
  Mountains, 
  gives 
  an 
  approxi- 
  

   mate 
  idea 
  of 
  their 
  position 
  in 
  a 
  mineralogical 
  classification. 
  The 
  sub- 
  

   joined 
  average 
  is 
  prepared 
  from 
  thirty-four 
  analyses 
  : 
  

  

  Specific 
  gravity 
  : 
  1. 
  325. 
  

  

  Per 
  cent. 
  

  

  Water 
  6. 
  436 
  

  

  Carbon, 
  fixed 
  52.617 
  

  

  Volatile 
  matter 
  . 
  34.096 
  

  

  Ash 
  - 
  6.835 
  

  

  In 
  contradistinction 
  to 
  the 
  above 
  is 
  the 
  total 
  average 
  of 
  the 
  anthra- 
  

   cite 
  coals, 
  prepared 
  from 
  ten 
  analyses, 
  all 
  that 
  were 
  available 
  at 
  the 
  

   time 
  of 
  writiug 
  : 
  

  

  Specific 
  gravity 
  : 
  1.686. 
  

  

  Per 
  cent. 
  

  

  Water 
  2.898 
  

  

  Carbon, 
  fixed 
  73.690 
  

  

  Volatile 
  matter 
  16. 
  435 
  

  

  Ash 
  6.987 
  

  

  From 
  the 
  above 
  tables 
  it 
  will 
  be 
  seen 
  that 
  the 
  average 
  specific 
  gravity 
  

   varies 
  to 
  a 
  certain 
  extent 
  commensurate 
  with 
  the 
  increase 
  of 
  non-com- 
  

   bustible 
  component 
  parts. 
  Of 
  all 
  the 
  constituents 
  the 
  volatile 
  are 
  the 
  

   most 
  constant 
  in 
  their 
  relative 
  proportion, 
  excepting 
  the 
  coal 
  from 
  the 
  

   Gunnison 
  and 
  the 
  Elk 
  Mountains. 
  Having 
  but 
  comparatively 
  few 
  

   analyses 
  from 
  each 
  locality, 
  the 
  table 
  showing 
  averages 
  has 
  not 
  the 
  same 
  

   value 
  that 
  a 
  larger 
  number 
  would 
  have 
  given 
  it. 
  As 
  an 
  indication, 
  how- 
  

   ever, 
  serving 
  for 
  comparison, 
  it 
  may 
  answer. 
  In 
  the 
  United 
  States 
  

   Geological 
  Report, 
  1873, 
  p. 
  112, 
  a 
  large 
  number 
  of 
  coal 
  analyses 
  will 
  be 
  

   found, 
  furnishing 
  not 
  only 
  data 
  regarding 
  Colorado 
  coals, 
  but 
  also 
  from 
  

   other 
  regions 
  where 
  they 
  occur 
  in 
  formations 
  analogous 
  or 
  related 
  to 
  

   those 
  treated 
  of 
  in 
  this 
  chapter. 
  

  

  IRON-ORE. 
  

  

  In 
  connection 
  with 
  the 
  coal-bearing 
  strata 
  we 
  find 
  at 
  Trinidad 
  a 
  vari- 
  

   ety 
  of 
  iron 
  ore 
  known 
  popularly 
  as 
  "kidney-ore." 
  At 
  other 
  localities, 
  

   either 
  in 
  the 
  same 
  or 
  analogous 
  formations, 
  it 
  has 
  also 
  been 
  discovered, 
  

   and 
  in 
  some 
  instances 
  utilized. 
  It 
  is 
  mainly 
  a 
  carbonate 
  of 
  iron, 
  associ- 
  

   ated 
  with 
  silica, 
  silicate 
  of 
  alumina, 
  and 
  some 
  carbonates. 
  Upon 
  decom- 
  

   position 
  the 
  percentage 
  of 
  iron 
  increases, 
  through 
  the 
  loss 
  of 
  carbonic 
  

   acid. 
  Generally 
  the 
  quantity 
  of 
  iron 
  contained 
  in 
  "fresh" 
  ore 
  is 
  small. 
  It 
  

   occurs 
  in 
  the 
  shales 
  and 
  sandstones, 
  forming 
  more 
  or 
  less 
  irregular, 
  hard, 
  

   nodular 
  concretions. 
  These 
  resist 
  atmospheric 
  influences 
  more 
  success- 
  

   fully 
  than 
  the 
  material 
  surrounding 
  them, 
  and 
  weather 
  out, 
  forming 
  

   sometimes 
  deposits 
  not 
  unlike 
  those 
  of 
  river-drift. 
  

  

  Two 
  specimens 
  were 
  taken 
  from 
  the 
  immediate 
  vicinity 
  of 
  coal-beds 
  

   south 
  of 
  Trinidad. 
  No. 
  1 
  was 
  " 
  fresh 
  " 
  ; 
  color, 
  grey 
  ; 
  no 
  sign 
  of 
  decompo- 
  

   sition. 
  No. 
  2 
  was 
  decomposed, 
  color 
  reddish-brown, 
  Easily 
  broken 
  with 
  

   a 
  hammer. 
  It 
  formed 
  the 
  exterior 
  crust 
  of 
  one 
  of 
  the 
  nodules, 
  the 
  inte- 
  

   rior 
  of 
  which 
  was 
  still 
  in 
  its 
  undecoraposed 
  state. 
  

  

  An 
  analysis 
  for 
  iron 
  furnished 
  the 
  following 
  result 
  : 
  

  

  Per 
  cent. 
  Per 
  cent. 
  

  

  No. 
  1 
  : 
  a. 
  I>. 
  

  

  Iron 
  (calculated 
  as 
  metal) 
  4, 
  76 
  4. 
  35 
  

  

  No. 
  2: 
  

  

  Iron 
  (calculated 
  as 
  metal) 
  ^ 
  43. 
  93 
  43. 
  29 
  

  

  