﻿26 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  greatest 
  variety 
  of 
  species. 
  Professor 
  Kemp 
  1 
  has 
  listed 
  the 
  min- 
  

   erals 
  from 
  the 
  former 
  locality, 
  with 
  mention 
  of 
  their 
  more 
  

   important 
  characters. 
  The 
  Lyon 
  Mountain 
  locality 
  has 
  been 
  

   described 
  recently 
  in 
  a 
  detailed 
  manner 
  by 
  H. 
  P. 
  Whitlock. 
  2 
  

  

  As 
  a 
  rule 
  the 
  magnetites 
  show 
  little 
  alteration 
  or 
  effects 
  of 
  weath- 
  

   ering, 
  and 
  are 
  quite 
  fresh 
  at 
  the 
  surface. 
  The 
  only 
  chemical 
  change 
  

   at 
  all 
  common 
  is 
  oxidation 
  with 
  the 
  formation 
  of 
  hematite. 
  The 
  

   latter 
  is 
  usually 
  pseudomorphic 
  showing 
  the 
  characteristic 
  granular 
  

   structure 
  and 
  octahedral 
  parting 
  of 
  the 
  magnetite 
  — 
  the 
  form 
  

   known 
  as 
  martite. 
  It 
  occurs 
  sparingly 
  in 
  several 
  deposits, 
  but 
  in 
  

   quantity 
  only 
  on 
  Arnold 
  hill 
  where 
  the 
  so 
  called 
  " 
  blue 
  " 
  veins 
  

   are 
  practically 
  solid 
  hematite. 
  The 
  oxidation 
  of 
  magnetite 
  to 
  

   hematite 
  is 
  accomplished 
  very 
  slowly 
  under 
  ordinary 
  atmospheric 
  

   conditions, 
  and 
  it 
  seems 
  to 
  have 
  been 
  induced 
  in 
  these 
  deposits 
  by 
  

   some 
  special 
  agency 
  connected 
  probably 
  with 
  underground 
  water 
  

   circulations. 
  There 
  are 
  bodies 
  of 
  unaltered 
  magnetite 
  in 
  the 
  same 
  

   vicinity. 
  

  

  Shape 
  of 
  the 
  deposits 
  

  

  The 
  Adirondack 
  deposits 
  occur 
  in 
  a 
  variety 
  of 
  forms 
  such 
  as 
  

   are 
  common 
  to 
  the 
  magnetites 
  found 
  in 
  gneisses 
  and 
  schists 
  else- 
  

   where. 
  They 
  have 
  been 
  designated 
  by 
  different 
  writers 
  as 
  beds, 
  

   veins, 
  pods, 
  shoots, 
  lenses 
  etc., 
  depending 
  upon 
  their 
  particular 
  

   development 
  in 
  the 
  locality 
  investigated. 
  

  

  In 
  general 
  the 
  bodies 
  have 
  a 
  much 
  greater 
  extent 
  along 
  the 
  

   strike 
  and 
  dip 
  than 
  at 
  right 
  angles 
  thereto, 
  and 
  show 
  a 
  more 
  or 
  

   less 
  lenticular 
  form 
  in 
  horizontal 
  section, 
  wider 
  at 
  the 
  middle 
  and 
  

   tapering 
  toward 
  either 
  end. 
  In 
  some 
  cases 
  they 
  are 
  so 
  prolonged 
  

   in 
  the 
  direction 
  of 
  strike 
  that 
  they 
  are 
  better 
  described 
  as 
  tabular 
  

   bodies, 
  their 
  regularity 
  of 
  width 
  being 
  like 
  that 
  found 
  in 
  a 
  bed 
  or 
  

   stratum, 
  a 
  resemblance 
  that 
  has 
  been 
  emphasized 
  by 
  some 
  geol- 
  

   ogists 
  as 
  evidence 
  of 
  a 
  sedimentary 
  derivation. 
  The 
  tabular 
  and 
  

   elongated 
  lenticular 
  bodies 
  are 
  more 
  abundant 
  in 
  the 
  northern 
  and 
  

   western 
  Adirondacks. 
  The 
  Lyon 
  Mountain, 
  Arnold 
  hill 
  and 
  St 
  

   Lawrence 
  county 
  districts 
  afford 
  examples. 
  The 
  greatest 
  irregu- 
  

   larity 
  of 
  form 
  prevails 
  in 
  the 
  eastern 
  districts, 
  particularly 
  those 
  

   of 
  Essex 
  county, 
  where 
  the 
  deposits 
  often 
  exhibit 
  a 
  puzzling 
  com- 
  

   plexity 
  of 
  pinches, 
  swells 
  and 
  sharply 
  compressed 
  folds 
  not 
  observ- 
  

   able 
  in 
  other 
  sections. 
  

  

  1 
  Geology 
  of 
  the 
  Magnetites 
  near 
  Port 
  Henry. 
  Amer. 
  Inst. 
  Min. 
  Eng. 
  

   Trans, 
  v. 
  27. 
  1897. 
  

  

  2 
  Minerals 
  from 
  Lyon 
  Mountain. 
  N.Y. 
  State 
  Mus. 
  Bui. 
  107. 
  1907. 
  

  

  