﻿J. 
  B. 
  Wmplehy, 
  etc. 
  — 
  Custerite: 
  A 
  New 
  Mineral. 
  385 
  

  

  Art. 
  XXXV. 
  — 
  Custerite 
  : 
  A 
  New 
  Contact 
  Metamorjphic 
  

   Mineral 
  ; 
  by 
  J. 
  B. 
  Umpleby, 
  W. 
  T. 
  Schaller, 
  and 
  

   E. 
  S. 
  Laesen. 
  

  

  Introduction. 
  

  

  The 
  new 
  mineral 
  here 
  described 
  is 
  a 
  hydrous 
  flue-silicate 
  of 
  

   calcium 
  which 
  in 
  thin 
  section, 
  in 
  parallel 
  light, 
  resembles 
  a 
  

   pyroxene 
  but 
  with 
  crossed 
  nicols 
  suggests 
  albite. 
  It 
  was 
  col- 
  

   lected 
  by 
  one 
  of 
  the 
  authors 
  (J. 
  B. 
  ITmpleby) 
  in 
  the 
  fall 
  of 
  

   1912, 
  from 
  a 
  contact 
  zone 
  three 
  and 
  one-half 
  miles 
  southwest 
  

   of 
  Mackay, 
  Custer 
  County, 
  Idaho. 
  The 
  zone 
  is 
  worked 
  for 
  

   copper, 
  the 
  ore 
  occurring 
  principally 
  as 
  irregular 
  shoots 
  in 
  

   granite 
  porphyry, 
  well 
  removed 
  from 
  its 
  contact 
  with 
  the 
  

   invaded 
  Mississippian 
  limestone. 
  The 
  ore 
  minerals, 
  principal 
  

   among 
  them 
  chalcopyrite 
  and 
  its 
  oxidation 
  products, 
  are 
  inti- 
  

   mately 
  associated 
  with 
  garnet, 
  diopside, 
  magnetite, 
  fluorite, 
  and 
  

   other 
  contact 
  minerals 
  in 
  bodies 
  which 
  are 
  nearly 
  coincident 
  

   in 
  extent 
  with 
  original 
  limestone 
  inclusions.* 
  In 
  some 
  of 
  

   these 
  inclusions 
  none 
  of 
  the 
  original 
  limestone 
  remains, 
  though 
  

   locally 
  its 
  bedded 
  structure 
  is 
  preserved 
  in 
  the 
  garnet-diopside 
  

   rock, 
  but 
  in 
  others 
  a 
  core 
  of 
  unaltered 
  blue 
  limestone 
  grades 
  

   outward 
  through 
  pale-blue, 
  partly 
  recrystallized 
  limestone 
  into 
  

   white 
  marble 
  and 
  on 
  into 
  a 
  zone 
  made 
  up 
  largely 
  of 
  garnet, 
  

   diopside, 
  and 
  magnetite. 
  The 
  new 
  mineral 
  was 
  collected 
  from 
  

   between 
  the 
  garnet-diopside 
  and 
  marble 
  zones 
  which 
  fringe 
  

   one 
  of 
  these 
  inclusions. 
  

  

  The 
  name 
  custerite, 
  after 
  the 
  county 
  in 
  which 
  it 
  was 
  found, 
  

   is 
  proposed 
  for 
  the 
  mineral 
  here 
  described. 
  

  

  Occurrence 
  and 
  Genesis. 
  

  

  The 
  mineral 
  custerite 
  was 
  found 
  about 
  200 
  feet 
  within 
  the 
  

   margin 
  of 
  a 
  great 
  limestone 
  inclusion 
  which 
  outcrops 
  over 
  an 
  

   area 
  of 
  about 
  10,000 
  square 
  feet 
  on 
  the 
  first 
  divide 
  north 
  of 
  

   the 
  Empire 
  (formerly 
  the 
  White 
  Knob) 
  mine. 
  It 
  occurs 
  inti- 
  

   mately 
  associated 
  with 
  magnetite 
  and 
  much 
  less 
  garnet 
  and 
  

   diopside. 
  Hand 
  specimens 
  of 
  usual 
  size 
  may 
  be 
  secured 
  which 
  

   show 
  magnetite 
  and 
  custerite 
  in 
  about 
  equal 
  amount, 
  and 
  

   apparently 
  of 
  contemporaneous 
  origin. 
  The 
  garnet 
  and 
  diop- 
  

   side 
  occur 
  in 
  irregular 
  scattered 
  crystals 
  many 
  of 
  which 
  are 
  

   euhedral. 
  The 
  relation 
  of 
  the 
  custerite 
  to 
  these 
  minerals 
  is 
  

   similar 
  to 
  the 
  relation 
  of 
  calcite 
  to 
  them 
  on 
  the 
  margins 
  of 
  

   garnet-diopside 
  areas 
  and 
  suggests 
  that 
  they 
  were 
  developed 
  

  

  *This 
  interpretation, 
  which 
  will 
  be 
  amplified 
  in 
  a 
  report 
  on 
  the 
  ore 
  

   deposits 
  by 
  J. 
  B. 
  ITmpleby, 
  is 
  at 
  variance 
  with 
  tbat 
  advanced 
  by 
  Kemp, 
  J. 
  F., 
  

   and 
  G-nnther, 
  C. 
  G., 
  The 
  White 
  Knob 
  Copper 
  Deposits, 
  Mackay, 
  Idaho 
  : 
  Am. 
  

   Inst. 
  Min. 
  Eng., 
  Bull. 
  No. 
  14, 
  pp. 
  301-328, 
  14 
  figs., 
  March, 
  1907. 
  

  

  