﻿LAURENTIAN 
  LIMESTONES 
  OF 
  NORTH 
  AMERICA. 
  95 
  

  

  There 
  is, 
  however, 
  another 
  class 
  of 
  graphites 
  belonging 
  to 
  the 
  

   stratification, 
  and 
  evidently 
  of 
  sedimentary 
  origin, 
  containing 
  a 
  

   large 
  admixture 
  of 
  earthy 
  materials, 
  such 
  as 
  sand 
  and 
  clay. 
  These 
  

   graphites 
  are 
  generally 
  amorphous, 
  or 
  but 
  imperfectly 
  crystalline, 
  

   and 
  ordinarily 
  give 
  a 
  much 
  darker 
  streak 
  than 
  the 
  purer 
  varieties. 
  

   To 
  this 
  second 
  class 
  belongs 
  the 
  earthy 
  graphite 
  from 
  Clarendon, 
  

   Ontario, 
  already 
  described, 
  and 
  that 
  of 
  many 
  other 
  localities, 
  where 
  

   the 
  mineral 
  has 
  been 
  formed 
  by 
  the 
  alteration 
  of 
  more 
  or 
  less 
  car- 
  

   bonaceous 
  layers 
  in 
  schistose 
  rocks. 
  The 
  impure 
  plumbaginous 
  

   schists 
  from 
  the 
  Quebec 
  group 
  of 
  the 
  Eastern 
  Townships 
  of 
  the 
  

   province 
  of 
  Quebec 
  ; 
  the 
  beds 
  of 
  graphite 
  in 
  the 
  micaceous 
  schists 
  

   of 
  eastern 
  Massachusetts, 
  at 
  Sturbridge, 
  Worcester 
  and 
  elsewhere, 
  

   which 
  are 
  now 
  recognized 
  to 
  be 
  altered 
  beds 
  of 
  coal 
  ; 
  those 
  of 
  the 
  

   French 
  Alps, 
  which 
  are 
  associated 
  with 
  fossil 
  plants, 
  and 
  those 
  of 
  

   Passau, 
  in 
  Bavaria, 
  where 
  the 
  mineral 
  is 
  disseminated 
  in 
  gneiss 
  

   of 
  Laurentian 
  age, 
  are 
  also 
  examples 
  of 
  this 
  second 
  class 
  of 
  graph- 
  

   ites. 
  To 
  these 
  we 
  may 
  add 
  the 
  graphite 
  of 
  Borrowdale, 
  in 
  

   Cumberland, 
  which 
  is 
  found 
  in 
  lenticular 
  masses 
  in 
  altered 
  slates, 
  

   and 
  the 
  beds 
  of 
  graphite 
  in 
  mica-slate, 
  in 
  New 
  Hampshire, 
  which 
  

   in 
  some 
  cases 
  passes 
  into 
  a 
  plumbaginous 
  mica-slate, 
  holding 
  gar- 
  

   nets. 
  In 
  describing 
  the 
  latter 
  deposits, 
  Dr. 
  Jackson 
  has 
  observed 
  

   that 
  in 
  the 
  town 
  of 
  Goshen 
  the 
  beds 
  of 
  graphite 
  are 
  intersected 
  

   with 
  cross 
  veins, 
  which 
  are 
  filled 
  with 
  pure 
  foliated 
  graphite. 
  

  

  These 
  graphites 
  of 
  the 
  second 
  class 
  are 
  distinguished 
  not 
  only 
  

   by 
  the 
  large 
  proportion 
  of 
  silicious 
  and 
  argillaceous 
  matters 
  with 
  

   which 
  they 
  are 
  mingled, 
  but 
  also 
  by 
  the 
  very 
  general 
  absence 
  of 
  

   crystalline 
  texture. 
  This 
  is 
  so 
  evident 
  a 
  characteristic, 
  that 
  Sir 
  

   Benjamin 
  Broclie, 
  in 
  his 
  recent 
  researches 
  on 
  the 
  chemical 
  relations 
  

   of 
  graphite, 
  distinguishes 
  two 
  varieties 
  — 
  the 
  amorphous, 
  including 
  

   that 
  from 
  Borrowdale 
  and 
  from 
  Passau, 
  and 
  the 
  lamellar 
  or 
  crys- 
  

   talline, 
  represented 
  by 
  the 
  graphite 
  associated 
  with 
  quartz 
  from 
  

   Ceylon, 
  and 
  that 
  from 
  Ticoncleroga, 
  New 
  York 
  (Philos. 
  Transac- 
  

   tions 
  1859, 
  page 
  249), 
  the 
  latter 
  of 
  which 
  belongs 
  to 
  Laurentain 
  

   veins. 
  The 
  graphites 
  from 
  New 
  Brunswick 
  and 
  from 
  Greenland, 
  

   according 
  to 
  him, 
  approach 
  to 
  anthracite 
  in 
  character, 
  and 
  prob- 
  

   ably, 
  like 
  that 
  of 
  Massachusetts, 
  pass 
  into 
  this 
  variety 
  of 
  mineral 
  

   carbon 
  (Lyell. 
  Geol. 
  Journal, 
  I, 
  199. 
  — 
  HitchcocMs 
  Geol. 
  Mass., 
  

   page 
  127). 
  Between 
  the 
  amorphous 
  graphite 
  of 
  Broclie, 
  repre- 
  

   sented 
  by 
  that 
  of 
  Borrowdale 
  and 
  Passau, 
  and 
  the 
  lamellar 
  variety 
  

   from 
  Ceylon 
  and 
  from 
  the 
  Laurentian 
  veins 
  of 
  North 
  America, 
  

   may 
  be 
  placed 
  the 
  interstratified 
  graphites 
  of 
  New 
  Hampshire 
  and 
  

  

  