﻿LAURENTIAN 
  LIMESTONES 
  OF 
  NORTH 
  AMERICA, 
  63 
  

  

  1832, 
  published 
  a 
  description 
  of 
  the 
  minerals 
  of 
  Orange 
  county, 
  

   New 
  York 
  (Amef. 
  Jour. 
  Science 
  [1], 
  xxi, 
  321). 
  Prof. 
  H. 
  D. 
  Rogers 
  

   also, 
  in 
  his 
  Final 
  Report 
  on 
  the 
  Geology 
  of 
  New 
  Jersey, 
  notices 
  

   the 
  occurrence 
  of 
  aggregates 
  of 
  carbonate 
  of 
  lime, 
  with 
  feldspar, 
  

   hornblende, 
  pyroxene, 
  sphene, 
  spinel, 
  etc., 
  forming 
  dykes 
  or 
  veins 
  

   in 
  the 
  crystalline 
  limestone 
  of 
  that 
  region 
  ; 
  and 
  shows, 
  moreover, 
  

   that 
  the 
  franklinite 
  and 
  red 
  zinc 
  ore, 
  with 
  their 
  associated 
  minerals, 
  

   occur 
  in 
  calcareous 
  veins. 
  Finally, 
  Mr. 
  W. 
  P. 
  Blake, 
  in 
  describ- 
  

   ing 
  a 
  locality 
  of 
  the 
  first 
  mentioned 
  group 
  of 
  minerals 
  in 
  Vernon, 
  

   New 
  Jersey, 
  declares 
  it 
  to 
  have 
  the 
  characters 
  of 
  a 
  segregated 
  

   vein 
  (Amei\ 
  Jour. 
  Science 
  [2], 
  xiii, 
  116). 
  Despite 
  these 
  observa- 
  

   tions, 
  however, 
  Emmons 
  and 
  Mather 
  did 
  not 
  regard 
  the 
  distinction 
  

   which 
  evidently 
  exists 
  between 
  the 
  bedded 
  limestones 
  and 
  the 
  

   veins, 
  many 
  of 
  which, 
  from 
  a 
  predominance 
  of 
  carbonate 
  of 
  lime 
  

   in 
  their 
  composition, 
  became 
  confounded 
  in 
  their 
  eyes 
  with 
  the 
  

   limestones 
  themselves, 
  leading 
  both 
  of 
  these 
  observers, 
  as 
  we 
  

   have 
  already 
  seen, 
  to 
  admit 
  the 
  existence 
  of 
  eruptive 
  limestones 
  ; 
  

   while 
  Emmons 
  even 
  concluded 
  that 
  all 
  the 
  limestones 
  of 
  the 
  

   northern 
  Laurentian 
  district 
  of 
  New 
  York 
  were 
  non-stratified, 
  and 
  

   of 
  eruptive 
  origin. 
  A 
  careful 
  geognostic 
  study 
  will, 
  however, 
  we 
  

   think, 
  suffice 
  to 
  show 
  that 
  by 
  far 
  the 
  greater 
  part 
  of 
  the 
  calcareous 
  

   rocks 
  in 
  the 
  Laurentian 
  system 
  of 
  North 
  America 
  are 
  stratified, 
  

   and 
  that 
  the 
  so-called 
  eruptive 
  limestones 
  are 
  really 
  calcareous 
  

   veinstones, 
  or 
  endogenous 
  rocks, 
  generally 
  including 
  foreign 
  

   minerals, 
  such 
  as 
  pyroxene, 
  scapolite, 
  orthoclase, 
  quartz, 
  etc. 
  

   These, 
  in 
  other 
  veins, 
  predominate 
  to 
  the 
  exclusion 
  of 
  carbonate 
  

   of 
  lime, 
  and 
  then 
  present 
  aggregates 
  approaching 
  in 
  composition 
  

   to 
  the 
  granitic 
  veinstones, 
  into 
  which 
  they 
  pass 
  by 
  the 
  exclusion 
  

   of 
  calcareous 
  and 
  magnesian 
  minerals, 
  such 
  as 
  calcite, 
  apatite, 
  

   pyroxene, 
  magnesian 
  mica, 
  scapolite, 
  etc. 
  These 
  species 
  serve 
  to 
  

   distinguish 
  the 
  veins 
  of 
  the 
  limestone 
  groups 
  from 
  the 
  proper 
  

   granitic 
  veinstones, 
  in 
  which 
  latter, 
  orthoclase, 
  albite, 
  quartz 
  and 
  

   muscovite 
  are 
  the 
  characteristic 
  minerals. 
  

  

  The 
  so-called 
  Primitive 
  Gneiss 
  formation 
  of 
  Scandinavia 
  has 
  

   long 
  been 
  regarded 
  by 
  the 
  Geological 
  Survey 
  as 
  belonging 
  to 
  the 
  

   Laurentian 
  system 
  (Esquisse 
  Geologique 
  du 
  Canada, 
  p. 
  17 
  : 
  Geo- 
  

   logy 
  of 
  Canada, 
  p. 
  586), 
  and 
  is 
  associated 
  with 
  crystalline 
  lime- 
  

   stones, 
  which 
  have 
  afforded 
  most 
  of 
  the 
  minerals 
  that 
  are 
  to 
  be 
  

   met 
  with 
  in 
  the 
  Laurentian 
  limestones 
  of 
  North 
  America, 
  together 
  

   with 
  many 
  additional 
  species. 
  Such 
  of 
  these 
  minerals 
  as 
  are 
  com- 
  

   mon 
  to 
  the 
  two 
  regions, 
  offer 
  close 
  resemblances, 
  not 
  only 
  in 
  their 
  

  

  