﻿706 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  thickness 
  and 
  remarkably 
  free 
  from 
  injurious 
  admixture. 
  At 
  the 
  

   surface 
  these 
  beds 
  are 
  discolored, 
  but 
  further 
  down 
  become 
  a 
  

   clear, 
  greenish 
  white, 
  and 
  have 
  a 
  scaly 
  or 
  fibrous 
  structure. 
  

  

  In 
  seeking 
  the 
  origin 
  of 
  these 
  deposits, 
  their 
  structure 
  and 
  

   relations 
  to 
  surrounding 
  rock, 
  their 
  composition 
  and 
  the 
  occur- 
  

   rence 
  of 
  analogous 
  deposits 
  in 
  other 
  portions 
  of 
  the 
  region 
  are 
  to 
  

   be 
  considered. 
  All 
  of 
  the 
  talc 
  deposits 
  examined 
  lie 
  in 
  that 
  por- 
  

   tion 
  of 
  the 
  belt 
  shown 
  on 
  the 
  map, 
  and 
  these, 
  in 
  every 
  case, 
  are 
  

   in 
  the 
  limestone. 
  They 
  form 
  beds 
  lying 
  in 
  this 
  rock 
  and 
  show 
  

   every 
  evidence 
  of 
  being 
  interstratified 
  deposits. 
  Nothing 
  was 
  

   seen 
  to 
  indicate 
  that 
  the 
  talc 
  bodies 
  are 
  veins, 
  though 
  they 
  are 
  

   commonly 
  referred 
  to 
  as 
  such. 
  In 
  working 
  the 
  deposits 
  masses 
  

   are 
  sometimes 
  struck 
  consisting 
  largely 
  of 
  tremolite, 
  which, 
  as 
  

   stated 
  by 
  Sahlen,* 
  has 
  given 
  rise 
  to 
  the 
  theory 
  that 
  the 
  talc 
  is 
  

   derived 
  from 
  amphibole. 
  The 
  presence 
  of 
  these 
  tremolite 
  masses 
  

   certainly 
  points 
  strongly 
  to 
  such 
  an 
  origin, 
  as 
  does 
  also 
  the 
  fibrous 
  

   structure 
  of 
  the 
  talc. 
  To 
  get 
  further 
  evidence 
  upon 
  this 
  point, 
  

   sections 
  were 
  prepared 
  from 
  specimens 
  of 
  the 
  fibrous 
  talc, 
  an 
  

   effort 
  being 
  made 
  to 
  procure 
  a 
  fairly 
  complete 
  series 
  from 
  soft 
  

   talc 
  to 
  tremolite. 
  Under 
  the 
  microscope 
  these 
  sections 
  all 
  show 
  

   the 
  presence 
  of 
  tremolite. 
  The 
  harder 
  varieties 
  contain 
  nothing 
  

   else 
  excepting 
  quartz, 
  to 
  which 
  mineral 
  the 
  hardness 
  is 
  doubtless 
  

   largely 
  due. 
  Even 
  the 
  softest 
  specimens 
  are 
  seen 
  to 
  be 
  largely 
  

   composed 
  of 
  very 
  finely 
  fibrous 
  tremolite, 
  probably 
  somewhat 
  

   altered, 
  with 
  high 
  interference 
  colors 
  and 
  extinction 
  angle 
  of 
  

   sixteen 
  to 
  eighteen 
  degrees. 
  Thus 
  it 
  seems 
  that 
  much 
  that 
  is 
  

   called 
  talc 
  contains 
  in 
  reality 
  considerable 
  tremolite, 
  only 
  the 
  

   scaly 
  varieties 
  being 
  true 
  talc. 
  Microscopic 
  evidence 
  then 
  

   strongly 
  supports 
  the 
  theory 
  that 
  the 
  talc 
  is 
  derived 
  from 
  tremo- 
  

   lite. 
  When 
  to 
  this 
  is 
  added 
  the 
  fact 
  already 
  stated 
  that 
  the 
  

   crystalline 
  limestone 
  elsewhere 
  in 
  the 
  region 
  shows 
  tremolitic 
  

   varieties 
  which 
  pass 
  into 
  tremolite 
  schist, 
  the 
  evidence 
  becomes 
  

   practically 
  conclusive. 
  

  

  The 
  tremolite 
  schists 
  represent 
  portions 
  of 
  the 
  limestone 
  for- 
  

   mation 
  which 
  contained 
  a 
  large 
  amount 
  of 
  silicious 
  sediment. 
  

   Metamorphism 
  produced 
  crystallization 
  of 
  the 
  mingled 
  calcareous, 
  

  

  * 
  A. 
  Sahlen.— 
  The 
  Talc 
  Industry 
  of 
  the 
  Gouverneur 
  District, 
  N. 
  Y., 
  Trans. 
  Am. 
  Inst. 
  Min. 
  

   Eng., 
  XXI, 
  p. 
  583; 
  The 
  Mineral 
  Industry, 
  I, 
  p. 
  435. 
  

  

  