﻿324 
  G. 
  P. 
  Merrill 
  — 
  Calcium 
  Phosphate 
  in 
  Meteoric 
  Stones. 
  

  

  These 
  results 
  agree 
  in 
  all 
  respects 
  with 
  those 
  given 
  in 
  my 
  

   previous 
  paper, 
  and 
  show 
  with 
  seeming 
  conclusiveness 
  that 
  a 
  

   calcium 
  phosphate 
  is 
  a 
  very 
  general 
  if 
  not 
  universal 
  constituent 
  

   of 
  meteoric 
  stones, 
  and 
  that, 
  further, 
  it 
  differs 
  from 
  normal 
  

   apatite 
  in 
  its 
  optical 
  and 
  other 
  physical 
  characteristics, 
  which 
  

   may 
  be 
  summed 
  up 
  as 
  below, 
  a 
  repetition 
  in 
  part 
  of 
  what 
  I 
  

   have 
  previously 
  stated 
  : 
  

  

  Occurrence 
  sporadic, 
  without 
  crystal 
  form, 
  very 
  brittle, 
  

   colorless 
  ; 
  cleavage 
  for 
  the 
  most 
  part 
  lacking 
  though 
  sometimes 
  

   imperfect 
  and 
  interrupted, 
  showing 
  angles 
  of 
  60° 
  and 
  120° 
  ; 
  

   optically 
  biaxial 
  and 
  positive 
  (?), 
  birefringence 
  weak, 
  less 
  than 
  

   0-005, 
  refractive 
  indices 
  o=l-623±0*002and 
  7=l-627db0-005 
  ; 
  

   no 
  pleochroism 
  and 
  often 
  undulatory 
  extinction, 
  polarizing 
  in 
  

   light 
  and 
  dark 
  colors, 
  sometimes 
  almost 
  isotropic 
  ; 
  easily 
  soluble 
  

   in 
  cold 
  dilute 
  nitric 
  acid 
  and 
  less 
  so 
  in 
  hydrochloric, 
  giving 
  

   solutions 
  reacting 
  for 
  calcium 
  and 
  phosphorus. 
  The 
  mineral 
  is 
  

   further 
  distinguished 
  from 
  normal 
  apatite 
  in 
  that 
  it 
  is 
  a 
  product 
  

   of 
  the 
  last 
  rather 
  than 
  the 
  first 
  stages 
  of 
  consolidation.* 
  Just 
  

   what 
  meaning 
  and 
  how 
  much 
  importance 
  is 
  to 
  be 
  attached 
  to 
  

   this 
  different 
  habit 
  of 
  the 
  phosphate 
  in 
  the 
  history 
  of 
  a 
  meteor- 
  

   ite 
  it 
  is 
  yet 
  too 
  early 
  to 
  say. 
  Obviously 
  it 
  bespeaks 
  conditions 
  

   governing 
  crystallization 
  unlike 
  those 
  which 
  prevailed 
  during 
  

   the 
  consolidation 
  of 
  terrestrial 
  rocks. 
  

  

  For 
  the 
  present 
  it 
  would 
  seem 
  best 
  to 
  designate 
  this 
  member 
  

   of 
  the 
  apatite 
  group 
  by 
  the 
  name 
  francolite, 
  with 
  which 
  it 
  

   most 
  nearly 
  agrees,f 
  as 
  was 
  done 
  in 
  the 
  paper 
  mentioned 
  above. 
  

   It 
  may 
  be 
  added 
  that 
  its 
  common 
  presence 
  in 
  optically 
  recog- 
  

   nizable 
  quantities 
  suggests 
  the 
  advisability 
  of 
  exercising 
  greater 
  

   care 
  in 
  the 
  determination 
  of 
  phosphorus 
  and 
  calcium 
  in 
  chemi- 
  

   cal 
  analyses 
  of 
  meteoric 
  stones. 
  

  

  * 
  In 
  his 
  description 
  of 
  the 
  meteorite 
  of 
  A.ngra 
  dos 
  Reis, 
  Tschermak 
  men- 
  

   tions 
  the 
  occurrence 
  of 
  abundant 
  small 
  colorless 
  granules, 
  without 
  cleavage, 
  

   weakly 
  doubly 
  refracting, 
  uniaxial 
  and 
  negative. 
  These 
  he 
  identified 
  as 
  

   apatite, 
  a 
  conclusion 
  borue 
  out 
  by 
  the 
  chemical 
  composition 
  of 
  the 
  silicate 
  

   portion 
  of 
  the 
  stone. 
  The 
  mineral 
  I 
  have 
  described, 
  which 
  apparently 
  is 
  

   quite 
  similar, 
  is, 
  however, 
  biaxial. 
  The 
  possibility 
  of 
  the 
  apparent 
  biaxial 
  

   interference 
  figures 
  being 
  those 
  of 
  a 
  uniaxial 
  mineral 
  cut 
  parallel 
  with 
  an 
  

   optic 
  axis 
  was 
  considered, 
  but 
  deemed 
  wholly 
  improbable 
  from 
  the 
  fact 
  that 
  

   in 
  not 
  one 
  of 
  the 
  many 
  sections 
  examined 
  was 
  I 
  able 
  to 
  find 
  a 
  uniaxial 
  

   figure. 
  It 
  seems 
  improbable 
  that 
  among 
  so 
  large 
  a 
  number 
  should 
  not 
  be 
  

   found 
  at 
  least 
  one. 
  did 
  such 
  exist. 
  

  

  fSee 
  Schaller, 
  Bull. 
  509, 
  U. 
  S. 
  Geol. 
  Surv., 
  p. 
  91, 
  1912. 
  

  

  