﻿LATJRENTIAN 
  LIMESTONES 
  OP 
  NORTH 
  AMERICA. 
  79 
  

  

  Babingtonite.— 
  This 
  rare 
  species, 
  which 
  belongs 
  to 
  the 
  pyrox- 
  

   ene 
  group, 
  is 
  said 
  to 
  be 
  found 
  upon 
  crystals 
  of 
  feldspar 
  in 
  Gou- 
  

   verneur, 
  New 
  York, 
  and 
  occurs 
  under 
  similar 
  conditions 
  in 
  veins 
  

   near 
  Arendal 
  in 
  Norway. 
  

  

  Pyrallolite. 
  — 
  This 
  species, 
  the 
  rensellaerite 
  cf 
  Emmons, 
  occurs 
  

   in 
  one 
  locality 
  in 
  radiating 
  columnar 
  masses, 
  with 
  quartz, 
  in 
  a 
  

   vein, 
  and 
  is 
  also 
  met 
  with 
  in 
  beds, 
  in 
  contact 
  with 
  serpentine, 
  with 
  

   pyroxenite, 
  and 
  in 
  another 
  case 
  with 
  limestone, 
  and 
  enclosing 
  

   scales 
  of 
  mica 
  and 
  of 
  graphite 
  (Geol. 
  Can., 
  page 
  470). 
  A 
  com- 
  

   pact 
  earthy 
  hydrous 
  silicate 
  of 
  magnesia, 
  having 
  the 
  characters 
  of 
  

   meerschaum 
  or 
  aphrodite, 
  and 
  the 
  composition 
  of 
  the 
  latter, 
  occurs 
  

   in 
  cavities 
  in 
  massive 
  renseliaerite 
  in 
  Grenville 
  (Ibid, 
  page 
  473). 
  

  

  Talc. 
  — 
  This 
  species 
  is 
  closely 
  related 
  to 
  the 
  last, 
  and 
  the 
  two 
  

   may 
  be 
  looked 
  upon 
  as 
  dimorphous 
  conditions 
  of 
  the 
  same 
  

   hydrous 
  silicate 
  of 
  magnesia. 
  In 
  the 
  Laurentian 
  series, 
  talc 
  seems 
  

   to 
  be 
  generally 
  replaced 
  by 
  pyrallolite, 
  but 
  in 
  one 
  instance 
  is 
  

   observed 
  mixed 
  with 
  carbonates 
  of 
  lime 
  and 
  magnesia, 
  in 
  such 
  

   proportions 
  as 
  to 
  give 
  rise 
  to 
  a 
  bed 
  of 
  impure 
  steatite 
  (Ibid. 
  

   page 
  469). 
  Prof. 
  H. 
  D. 
  Eogers 
  has 
  also 
  indicated 
  talc 
  as 
  occur- 
  

   ring 
  in 
  a 
  vein, 
  with 
  calcite, 
  pyroxene 
  and 
  spinel, 
  in 
  Sparta, 
  New 
  

   Jersey. 
  

  

  Gieseckite. 
  — 
  This 
  mineral, 
  which 
  the 
  careful 
  researches 
  of 
  

   Prof. 
  G. 
  J. 
  Brush 
  have 
  shown 
  to 
  be 
  identical 
  with 
  the 
  rock 
  

   named 
  dyssyntribite 
  by 
  Prof. 
  C. 
  U. 
  Shepard, 
  and 
  with 
  what 
  I 
  

   formerly 
  described 
  as 
  parophite, 
  is 
  found 
  in 
  large 
  crystals 
  in 
  

   northern 
  New 
  York, 
  associated 
  with 
  calcite, 
  brown 
  pyroxene 
  and 
  

   mica, 
  the 
  aggregate 
  doubtless 
  constituting 
  a 
  veinstone. 
  Wilsonite, 
  

   which, 
  notwithstanding 
  its 
  apparently 
  distinct 
  cleavage-form, 
  I 
  

   have 
  provisionally 
  included 
  under 
  the 
  head 
  of 
  gieseckite, 
  with 
  

   which 
  it 
  is 
  almost 
  identical 
  in 
  composition, 
  hardness 
  and 
  gravity, 
  

   occurs 
  also 
  in 
  a 
  veinstone, 
  in 
  Bathurst, 
  with 
  calcite, 
  apatite, 
  white 
  

   aluminous 
  pyroxene 
  and 
  serpentine. 
  The 
  mineral 
  which 
  I 
  once 
  

   described 
  by 
  the 
  name 
  of 
  algerite, 
  is 
  found 
  in 
  white 
  calcite, 
  among 
  

   the 
  Laurentian 
  limestones 
  of 
  Franklin, 
  New 
  Jersey, 
  and 
  has 
  a 
  com- 
  

   position 
  similar 
  to 
  that 
  of 
  gieseckite, 
  although 
  the 
  form 
  of 
  the 
  

   crystals 
  appears 
  to 
  be 
  a 
  square 
  prism. 
  Whatever 
  conclusions 
  may 
  

   eventually 
  be 
  arrived 
  at 
  relative 
  to 
  these 
  hydrous 
  silicates 
  of 
  alu- 
  

   mina 
  and 
  potash, 
  the 
  assumption 
  that 
  they 
  are 
  results 
  of 
  a 
  sup- 
  

   posed 
  alteration 
  of 
  nepheline, 
  scapolite, 
  etc., 
  is 
  purely 
  gratuitous. 
  

  

  