﻿LATJRENTIAN 
  LIMESTONES 
  OF 
  NORTH 
  AMERICA. 
  65 
  

  

  These 
  veins 
  are 
  seldom 
  of 
  great 
  extent, 
  and 
  near 
  Stockholm, 
  where 
  

   they 
  are 
  very 
  abundant, 
  rarely 
  exceed 
  300 
  feet 
  in 
  length. 
  

  

  At 
  the 
  iron 
  mines 
  in 
  the 
  island 
  of 
  Utoe, 
  where 
  the 
  ore 
  is 
  a 
  mix- 
  

   ture 
  of 
  magnetic 
  and 
  specular 
  oxyds, 
  occurring 
  in 
  beds, 
  with 
  horn- 
  

   blendic 
  rocks 
  passing 
  into 
  gneiss, 
  or 
  with 
  crystalline 
  limestone 
  

   holding 
  hornblende 
  and 
  mica, 
  granitoid 
  veinstones, 
  like 
  those 
  of 
  

   Arendal, 
  are 
  met 
  with, 
  holding 
  orthoclase 
  and 
  quartz, 
  with 
  tour- 
  

   maline 
  and 
  oxyd 
  of 
  tin, 
  together 
  with 
  the 
  rare 
  minerals, 
  petalite, 
  

   spodumene 
  and 
  lepidolite, 
  which 
  occupy 
  the 
  central 
  portion 
  of 
  the 
  

   veins. 
  This 
  association 
  is 
  the 
  more 
  worthy 
  of 
  notice, 
  as 
  the 
  only 
  

   other 
  known 
  locality 
  of 
  the 
  rare 
  mineral 
  petalite 
  (if 
  we 
  except 
  the 
  

   castor 
  of 
  Elba) 
  is 
  in 
  the 
  crystalline 
  limestone 
  of 
  Bolton, 
  Massa- 
  

   chusetts, 
  where 
  it 
  occurs 
  with 
  scapolite, 
  hornblende, 
  pyroxene, 
  

   chrysolite, 
  spinel, 
  apatite 
  and 
  sphene 
  — 
  the 
  characteristic 
  minerals 
  

   of 
  similar 
  limestones 
  in 
  Canada, 
  New 
  York 
  and 
  Scandinavia. 
  

  

  The 
  occurrence 
  of 
  oxyd 
  of 
  tin 
  in 
  the 
  above 
  associations 
  is 
  not 
  

   without 
  interest 
  in 
  relation 
  to 
  the 
  economic 
  mineralogy 
  of 
  the 
  

   Laurentian 
  system, 
  to 
  which 
  the 
  rocks 
  of 
  Utce 
  probably 
  belong 
  ; 
  

   and 
  it 
  is 
  well 
  to 
  recall, 
  in 
  this 
  connection, 
  the 
  existence 
  of 
  tin 
  ore 
  

   in 
  rocks, 
  probably 
  of 
  the 
  same 
  age, 
  at 
  Pitkaranta, 
  on 
  Lake 
  Ladoga, 
  

   in 
  Finland. 
  A. 
  rock 
  consisting 
  of 
  greenish 
  lamellar 
  hornblende, 
  

   with 
  garnet, 
  epidote 
  and 
  pyroxene, 
  is 
  there 
  interstratified 
  with 
  

   mica-slates, 
  sometimes 
  graphitic, 
  and 
  with 
  a 
  granitic 
  gneiss, 
  the 
  

   series 
  being 
  cut 
  by 
  granite-like 
  veins. 
  In 
  certain 
  beds 
  of 
  the 
  horn- 
  

   blenclic 
  rock, 
  magnetic 
  iron 
  is 
  disseminated 
  to 
  such 
  an 
  extent 
  that 
  

   the 
  mass 
  becomes 
  an 
  iron 
  ore. 
  This 
  is 
  occasionally 
  associated 
  

   with 
  oxyd 
  of 
  tin, 
  which 
  in 
  some 
  parts 
  predominates, 
  so 
  that 
  the 
  

   ore 
  is 
  mined 
  for 
  this 
  metal. 
  Other 
  hornblendic 
  beds 
  in 
  the 
  series 
  

   are 
  rich 
  in 
  copper 
  pyrites, 
  which 
  is 
  also 
  disseminated 
  in 
  the 
  mica- 
  

   slates, 
  and 
  is 
  sometimes 
  accompanied 
  by 
  sulphurets 
  of 
  lead, 
  zinc 
  

   and 
  molybdenum 
  {Durocher, 
  Ann. 
  des 
  Mines 
  [4], 
  xv, 
  316). 
  These 
  

   associations 
  should 
  not 
  be 
  overlooked 
  in 
  the 
  study 
  of 
  our 
  Lauren- 
  

   tian 
  rocks, 
  which 
  may 
  yet 
  be 
  found 
  to 
  be 
  tin-bearing. 
  

  

  Another 
  mineral 
  which 
  may 
  possibly 
  be 
  met 
  with 
  in 
  the 
  Lau- 
  

   rentian 
  rocks 
  of 
  Canada 
  is 
  gold, 
  since 
  small 
  quantities 
  of 
  the 
  pre- 
  

   cious 
  metal 
  are 
  found 
  in 
  several 
  localities 
  in 
  Scandinavia, 
  some 
  of 
  

   them 
  probably, 
  as 
  that 
  of 
  Barbo, 
  near 
  Arendal, 
  in 
  rocks 
  of 
  Lau- 
  

   rentian 
  age. 
  The 
  gold 
  of 
  Scandinavia 
  is, 
  however, 
  in 
  such 
  small 
  

   quantities 
  as 
  to 
  be 
  nowhere 
  made 
  the 
  object 
  of 
  mining. 
  Details 
  

   with 
  regard 
  to 
  it 
  are 
  given 
  by 
  Daubree 
  {Ann. 
  des 
  Mines 
  [4], 
  iv, 
  

   265) 
  and 
  by 
  Durocher 
  {Ibid. 
  [4], 
  xv, 
  371). 
  Small 
  quantities 
  of 
  

  

  