﻿JAN. 
  4, 
  1922 
  schaller: 
  gillespite 
  7 
  

  

  MINERALOGY.— 
  Gille 
  spite, 
  a 
  new 
  mineral.'^ 
  Wai^demar 
  T. 
  Schal- 
  

   LER, 
  U. 
  S. 
  Geological 
  Survey, 
  

  

  A 
  small 
  rock 
  specimen 
  collected 
  from 
  a 
  moraine 
  near 
  his 
  claim 
  near 
  

   the 
  head 
  of 
  Dry 
  Delta, 
  Alaska 
  range 
  (about 
  100 
  miles 
  S. 
  E. 
  of 
  Fair- 
  

   banks), 
  Alaska, 
  by 
  Mr. 
  Frank 
  Gillespie 
  (after 
  whom 
  the 
  mineral 
  is 
  

   named) 
  of 
  Richardson, 
  Alaska, 
  was 
  brought 
  to 
  the 
  Chemical 
  Labora- 
  

   tory 
  of 
  the 
  U. 
  S. 
  Geological 
  Survey 
  by 
  Dr. 
  Philip 
  S. 
  Smith 
  of 
  the 
  

   Survev. 
  

  

  The 
  rock 
  specimen 
  is 
  composed 
  chiefly 
  of 
  a 
  mica-like 
  mineral 
  

   (gillespite) 
  , 
  with 
  a 
  striking 
  red 
  color, 
  w^hich 
  could 
  not 
  be 
  identified 
  

   by 
  simple 
  tests. 
  By 
  chemical 
  analysis 
  the 
  mineral 
  proved 
  to 
  be 
  

   a 
  silicate 
  of 
  ferrous 
  iron 
  and 
  barium 
  with 
  the 
  composition 
  Fe"BaSi40io. 
  

   Two 
  other 
  minerals, 
  a 
  grayish 
  green 
  diopside 
  and 
  a 
  white 
  barium 
  feld- 
  

   spar, 
  with 
  the 
  red 
  gillespite, 
  compose 
  the 
  rock. 
  Several 
  other 
  minerals 
  

   are 
  seen 
  in 
  thin 
  sections 
  but 
  only 
  in 
  very 
  small 
  quantities. 
  The 
  

   mode 
  of 
  occurrence 
  of 
  the 
  rock 
  is 
  not 
  known 
  but 
  it 
  suggests 
  contact 
  

   metamorphism 
  with 
  the 
  development 
  of 
  abundant 
  barium 
  minerals. 
  

  

  The 
  red 
  gillespite 
  forms 
  thick 
  scaly 
  masses 
  from 
  one 
  to 
  five 
  milli- 
  

   meters 
  across 
  and 
  nearly 
  as 
  thick. 
  The 
  rock 
  mass 
  is 
  compact 
  and 
  

   although 
  no 
  crystal 
  faces 
  except 
  the 
  basal 
  plane 
  could 
  be 
  detected, 
  

   thin 
  sections 
  of 
  the 
  rock 
  suggest 
  an 
  occasional 
  terminal 
  plane 
  on 
  a 
  

   gillespite. 
  The 
  mineral 
  does 
  not 
  scale 
  off 
  like 
  mica 
  but 
  the 
  basal 
  

   cleavage 
  is 
  very 
  well 
  developed. 
  The 
  physical 
  properties 
  are 
  : 
  brittle, 
  

   H. 
  = 
  4, 
  sp. 
  gr. 
  = 
  3.33. 
  Luster 
  vitreous, 
  color 
  red, 
  streak 
  pink. 
  The 
  

   color 
  is 
  close 
  to 
  Ridgway's^ 
  "Pomegranate 
  Purple," 
  PI. 
  XII, 
  hue 
  no. 
  

   71, 
  tone 
  i, 
  and 
  to 
  "Spinel 
  Red," 
  PI. 
  XXVI, 
  hue 
  no. 
  71, 
  tone 
  b. 
  The 
  

   powder 
  approaches 
  "Geranium 
  Pink," 
  PI. 
  I, 
  hue 
  no. 
  3, 
  tone 
  d. 
  Trans- 
  

   lucent. 
  Optically 
  uniaxial, 
  negative, 
  birefringence 
  very 
  low, 
  strongly 
  

   pleochroic. 
  Refractive 
  indices: 
  e 
  (rose 
  red) 
  1.619, 
  co 
  (pale 
  pink 
  to 
  

   nearly 
  colorless) 
  1.621. 
  

  

  In 
  the 
  blow-pipe 
  flame, 
  gillespite 
  fuses 
  easily 
  and 
  quietly 
  to 
  a 
  black 
  

   non-magnetic 
  globule. 
  Heated 
  in 
  a 
  closed 
  tube, 
  it 
  darkens 
  and 
  as- 
  

   sumes 
  a 
  deep 
  violet 
  color, 
  the 
  original 
  red 
  color 
  being 
  regained 
  on 
  

   cooling. 
  Readily 
  decomposed 
  by 
  HCl, 
  without 
  gelatinization, 
  the 
  

   mineral 
  flakes 
  being 
  changed 
  to 
  glistening 
  flakes 
  of 
  silica 
  which 
  retain 
  

   the 
  shape 
  of 
  the 
  original 
  mineral. 
  These 
  residues 
  of 
  silica 
  are 
  doubly 
  

  

  ^ 
  Received 
  October 
  24, 
  1921. 
  Published 
  by 
  permission 
  of 
  the 
  Director, 
  U. 
  S. 
  Geological 
  

  

  Survey. 
  

  

  2 
  R. 
  RiDGWAY, 
  Color 
  standards 
  and 
  color 
  nomenclature. 
  Washington, 
  D. 
  C, 
  1912. 
  

  

  