﻿Lane 
  and 
  Sharjpless 
  — 
  Notes 
  on 
  Michigan 
  Minerals. 
  507 
  

  

  magnetite. 
  Garnet, 
  common 
  blue 
  green 
  hornblende 
  and 
  brown 
  

   mica 
  are 
  associated 
  with 
  it 
  at 
  times, 
  marking 
  stages 
  of 
  tran- 
  

   sition 
  to 
  ordinary 
  hornblende 
  schist. 
  

  

  § 
  4. 
  Judging 
  from 
  some 
  slight 
  variation 
  in 
  the 
  optical 
  prop- 
  

   erties 
  of 
  different 
  occurrences, 
  it 
  seems 
  likely 
  that 
  they 
  are 
  

   not 
  chemically 
  identical. 
  We 
  really 
  need 
  one 
  general 
  name 
  

   for 
  all 
  monoclinic 
  ferromagnesian 
  amphiboles, 
  without 
  regard 
  

   to 
  varieties 
  differing 
  merely 
  in 
  the 
  ratio 
  of 
  Mg 
  : 
  Fe. 
  To 
  amphi- 
  

   boles 
  of 
  this 
  kind 
  the 
  names 
  antholite, 
  kupfferite, 
  silf 
  bergite, 
  

   cummingtonite 
  and 
  griinerite 
  have 
  been 
  applied. 
  The 
  first 
  

   name, 
  antholite, 
  has 
  been 
  used 
  also 
  for 
  anthophyllite 
  and 
  is 
  

   confined 
  by 
  Dana 
  to 
  the 
  very 
  magnesian 
  varieties. 
  Typical 
  

   kupfferite 
  seems 
  to 
  be 
  chromiferous, 
  but 
  otherwise 
  practically 
  

   the 
  same 
  as 
  antholite, 
  thougli 
  its 
  physical 
  relations 
  to 
  the 
  

   amphiboles 
  have 
  not 
  been 
  determined 
  so 
  far 
  as 
  we 
  know. 
  

   Silfbergite* 
  has 
  8*39 
  per 
  cent 
  MnO, 
  as 
  well 
  as 
  3049 
  per 
  cent 
  

   FeO, 
  and 
  8*74: 
  per 
  cent 
  MgO. 
  The 
  name 
  cummingtonite 
  was 
  

   given 
  by 
  Dewey 
  f 
  to 
  a 
  mineral 
  from 
  Cummington, 
  Mass., 
  which 
  

   he 
  supposed 
  to 
  be 
  a 
  kind 
  of 
  epidote. 
  There 
  are 
  two 
  minerals 
  

   from 
  Cummington 
  which 
  have 
  been 
  taken 
  for 
  it, 
  as 
  the 
  original 
  

   description 
  is 
  not 
  very 
  explicit. 
  The 
  one 
  is 
  a 
  ferromagnesian 
  

   monoclinic 
  amphibole 
  in 
  truth, 
  with 
  only 
  a 
  mere 
  trace 
  of 
  

   MnO, 
  as 
  we 
  have 
  personally 
  found. 
  This 
  we 
  also 
  find 
  to 
  be 
  

   very 
  much 
  like 
  our 
  mineral 
  but 
  larger 
  and 
  coarser. 
  It 
  agrees 
  

   in 
  luster, 
  color, 
  brittleness 
  and 
  specific 
  weight, 
  3 
  2. 
  The 
  mineral 
  

   associations, 
  optical 
  properties 
  and 
  frequent 
  twinning 
  are 
  also 
  

   similar. 
  It 
  has 
  been 
  analyzed 
  by 
  Smith 
  and 
  Brush. 
  \ 
  

  

  The 
  other 
  mineral 
  is 
  a 
  manganese 
  mineral 
  akin 
  to 
  rhodonite. 
  

   It 
  has 
  been 
  analyzed 
  by 
  Muir§ 
  and 
  the 
  name 
  is 
  used 
  in 
  this 
  

   latter 
  sense 
  by 
  Rammelsberg, 
  Groth 
  and 
  other 
  writers 
  up 
  to 
  

   the 
  present 
  day. 
  

  

  With 
  griinerite 
  I 
  there 
  is 
  physically 
  the 
  closest 
  agreement. 
  

   Griinerite 
  however 
  is 
  supposed 
  to 
  contain 
  only 
  about 
  1 
  per 
  

   cent 
  MgO, 
  and 
  to 
  be 
  somewhat 
  heavier, 
  perhaps 
  also 
  more 
  bi- 
  

   refractive. 
  

  

  What 
  the 
  average 
  ratio 
  of 
  Mg 
  : 
  Fe 
  in 
  the 
  Michigan 
  amphi- 
  

   boles 
  under 
  consideration 
  is, 
  — 
  they 
  are 
  of 
  widespread 
  occur- 
  

   rence, 
  and 
  what 
  their 
  relations 
  to 
  kupfferite, 
  etc., 
  are 
  questions 
  

   that 
  require 
  work 
  upon 
  a 
  large 
  range 
  of 
  authentic 
  material 
  to 
  

   settle. 
  It 
  seems 
  indeed 
  possible, 
  in 
  view 
  of 
  the 
  tendency 
  to 
  

   repeated 
  twinning 
  parallel 
  to 
  100, 
  that 
  anthophyllite 
  may 
  be 
  

  

  *This 
  Journal, 
  xxvi, 
  p. 
  157. 
  f 
  This 
  Journal, 
  viii, 
  1824, 
  p. 
  59. 
  

  

  \ 
  This 
  Journal, 
  xvi, 
  1853, 
  p. 
  48. 
  § 
  Thomson's 
  Mineralogie, 
  vol. 
  i, 
  p. 
  493. 
  

  

  || 
  The 
  diaeresis 
  which 
  strictly 
  should 
  be 
  over 
  the 
  wis 
  dropped 
  by 
  Rammelsberg. 
  

   Tschermak, 
  Naumarm, 
  Zirkel, 
  Grroth 
  and 
  Chester, 
  and 
  sometimes 
  by 
  Levy 
  and 
  

   Lacroix 
  and 
  Max 
  Bauer, 
  while 
  Dana, 
  Lapparent, 
  Descloizeaux 
  and 
  Ramsay 
  retain 
  

   it. 
  

  

  