﻿Lane 
  and 
  Keller 
  — 
  Notes 
  on 
  Michigan 
  Minerals. 
  499 
  

  

  contraction 
  of 
  the 
  originally 
  liquid 
  mass 
  were 
  found 
  to 
  be, 
  for 
  

   instance 
  (fourth 
  series): 
  0-0771 
  at 
  1421°, 
  0*0760 
  at 
  1388° 
  

   0-0730 
  at 
  1319°, 
  0-0721 
  at 
  1305°, 
  0'0661 
  (sticky) 
  at 
  1190 
  r 
  

   0-0652 
  (very 
  sticky) 
  at 
  1163°, 
  -0628 
  at 
  1112°, 
  falling 
  off 
  event 
  

   ually 
  to 
  0-0285 
  at 
  1093°, 
  0-0223 
  at 
  914°, 
  0-U202 
  at 
  855°, 
  etc 
  

   Conversely 
  since 
  sudden 
  bulk 
  contraction 
  is 
  a 
  criterion 
  for 
  

   solidifying 
  point, 
  these 
  results 
  lead 
  to 
  sharp 
  values 
  for 
  this 
  

   datum. 
  

  

  Finally, 
  the 
  density 
  of 
  the 
  original 
  (cold) 
  rock 
  was 
  3-0178 
  

   (four 
  measurements) 
  and 
  the 
  density 
  of 
  the 
  (cold) 
  glass 
  after 
  

   fusion 
  2 
  717 
  (three 
  measurements). 
  Now 
  I 
  have 
  been 
  at 
  con- 
  

   siderable 
  pains 
  to 
  show 
  that 
  the 
  chemical 
  equilibrium 
  of 
  a 
  

   substance 
  (solid 
  or 
  liquid) 
  varies 
  with 
  pressure. 
  Since, 
  there- 
  

   fore, 
  the 
  glass 
  obtained 
  by 
  fusion 
  is 
  permanently 
  homogeneous 
  

   in 
  character, 
  structural 
  rock 
  texture 
  is 
  due 
  to 
  pressure 
  ; 
  i. 
  e. 
  

   pressure 
  induces 
  a 
  redistribution 
  of 
  molecules, 
  such 
  that 
  the 
  

   smallest 
  specific 
  volume 
  possible 
  under 
  the 
  given 
  conditions 
  

   may 
  result. 
  Hence 
  it 
  is 
  permissible 
  to 
  conceive 
  a 
  solution- 
  

   fusion 
  mechanism, 
  in 
  virtue 
  of 
  which, 
  by 
  the 
  mere 
  act 
  of 
  

   pressure, 
  volume 
  changes 
  of 
  an 
  order 
  of 
  even 
  13 
  per 
  cent 
  may 
  

   present 
  themselves. 
  

  

  Art. 
  LY1. 
  — 
  Notes 
  on 
  Michigan 
  Minerals 
  ;* 
  by 
  A. 
  C. 
  Lane, 
  

   H. 
  F. 
  Keller 
  and 
  F. 
  F. 
  Sharpless. 
  

  

  Contents: 
  1. 
  Chloritoid 
  [L. 
  and 
  K.] 
  § 
  1. 
  Historical 
  introduction. 
  2. 
  Sum- 
  

   mary 
  of 
  results. 
  3. 
  Physical 
  characters. 
  4. 
  Chemical 
  analysis. 
  5. 
  Paragenesis. 
  

   6. 
  Comparison 
  with 
  previous 
  results. 
  

  

  2. 
  Grunerite 
  [L. 
  and 
  S.] 
  § 
  l. 
  Historical 
  introduction. 
  2. 
  Physical 
  characters, 
  

   3. 
  Chemical 
  characters. 
  4. 
  Comparison 
  with 
  other 
  ferromagnesian 
  monoclioic 
  

   amphiboles. 
  

  

  3. 
  Riebeckite 
  [L.J 
  § 
  1. 
  Occurrence 
  and 
  optical 
  character. 
  

  

  1. 
  Chloritoid. 
  

  

  § 
  1. 
  This 
  mineral 
  has 
  been 
  known 
  to 
  occur 
  in 
  the 
  Upper 
  

   peninsula 
  of 
  Michigan 
  for 
  some 
  years. 
  It 
  was 
  first 
  described, 
  

   so 
  far 
  as 
  we 
  know, 
  by 
  Wadsworthf 
  as 
  occurring 
  at 
  Humboldt. 
  

   It 
  may 
  be 
  found 
  about 
  one 
  thousand 
  feet 
  S. 
  of 
  the 
  station 
  of 
  

   the 
  D. 
  S. 
  S. 
  and 
  A. 
  K. 
  R, 
  and 
  occurs 
  in 
  scales 
  2 
  mm 
  to 
  4 
  mm 
  

   broad. 
  It 
  also 
  occurs 
  at 
  points 
  east 
  and 
  west 
  in 
  the 
  same 
  

   range, 
  e. 
  g. 
  the 
  Fitch 
  Mine, 
  S. 
  24, 
  T. 
  47, 
  R 
  28, 
  and 
  from 
  S. 
  

   29, 
  T. 
  47, 
  R. 
  26. 
  Recently 
  we 
  have 
  found 
  it, 
  in 
  dark 
  green 
  

  

  * 
  Prom 
  the 
  laboratory 
  of 
  the 
  Michigan 
  Geological 
  .Survey, 
  with 
  the 
  permission 
  

   of 
  M. 
  E. 
  Wadsworth, 
  State 
  Geologist. 
  

  

  f 
  Bull. 
  Mus. 
  Comp. 
  Zool., 
  vol. 
  vii, 
  1880, 
  p. 
  45. 
  

  

  