﻿THE 
  GARNET 
  DEPOSITS 
  OF 
  WARREN 
  COUNTY, 
  

   NEW 
  YORK 
  

  

  BY 
  WILLIAM 
  J. 
  MILLER 
  

  

  INTRODUCTION 
  

   The 
  principal 
  garnet 
  mines 
  of 
  the 
  United 
  States 
  are 
  located 
  in 
  

   Warren 
  and 
  Essex 
  counties 
  of 
  the 
  eastern 
  Adirondack^, 
  those 
  of 
  

   Warren 
  county 
  — 
  especially 
  the 
  Hooper 
  and 
  Rogers 
  mines 
  below 
  

   described 
  — 
  being 
  the 
  greatest 
  producers. 
  All 
  the 
  Warren 
  

   county 
  mines 
  are 
  in 
  its 
  northwestern 
  portion 
  and 
  within 
  six 
  or 
  

   eight 
  miles 
  of 
  North 
  Creek 
  village 
  which 
  is 
  at 
  the 
  terminus 
  of 
  

   the 
  Adirondack 
  branch 
  of 
  the 
  Delaware 
  and 
  Hudson 
  Railroad. 
  

  

  GENERAL 
  GEOLOGIC 
  FEATURES 
  

   The 
  garnet 
  mines 
  of 
  Warren 
  county 
  lie 
  wholly 
  within 
  the 
  pre- 
  

   cambrian 
  rock 
  area 
  of 
  the 
  Adirondacks. 
  The 
  oldest 
  rocks 
  in 
  the 
  

   garnet 
  region 
  are 
  the 
  highly 
  metamorphosed 
  sediments 
  of 
  the 
  

   Grenville 
  series. 
  Detailed 
  mapping 
  by 
  the 
  writer 
  has 
  shown 
  ex- 
  

   tensive 
  areas 
  of 
  Grenville 
  which 
  are 
  unusually 
  rich 
  in 
  limestone 
  

   and 
  closely 
  associated 
  hornblende 
  gneiss. 
  

  

  Next 
  in 
  age 
  come 
  plutonic 
  igneous 
  rocks 
  such 
  as 
  syenite, 
  gran- 
  

   ite, 
  and 
  granite 
  porphyry 
  which 
  are 
  clearly 
  intrusions 
  into 
  the 
  

   Grenville 
  and 
  all 
  of 
  which 
  are 
  differentiation 
  products 
  from 
  the 
  

   same 
  great 
  cooling 
  magma. 
  Of 
  these 
  rocks 
  the 
  syenite 
  is, 
  per- 
  

   haps, 
  the 
  most 
  abundant. 
  It 
  is 
  a 
  medium 
  to 
  fairly 
  coarse 
  

   grained, 
  generally 
  quartzose 
  and 
  hornblendic 
  rock 
  with 
  some- 
  

   times 
  a 
  more 
  basic 
  variety 
  carrying 
  a 
  green 
  pyroxene. 
  The 
  gran- 
  

   ite 
  is 
  highly 
  quartzose 
  and 
  always 
  contains 
  hornblende 
  or 
  biotite 
  

   or 
  both. 
  The 
  granite 
  porphyry 
  is 
  biotitic 
  to 
  sometimes 
  horn- 
  

   blendic 
  with 
  large, 
  pink, 
  feldspar 
  crystals 
  imbedded 
  in 
  a 
  fine 
  to 
  

   medium 
  grained 
  matrix. 
  All 
  these 
  rocks 
  are 
  distinctly 
  gneissoid. 
  

   As 
  a 
  result 
  of 
  the 
  great 
  intrusion, 
  the 
  Grenville 
  in 
  some 
  cases 
  

   appears 
  to 
  have 
  been 
  pushed 
  upward 
  and 
  to 
  have 
  been 
  largely 
  

   removed 
  by 
  erosion 
  since 
  ; 
  in 
  other 
  cases 
  the 
  Grenville 
  was 
  more 
  

   or 
  less 
  engulfed 
  by, 
  or 
  involved 
  with, 
  the 
  molten 
  flood 
  as 
  shown 
  

   by 
  the 
  numerous 
  inclusions 
  and 
  the 
  areas 
  of 
  mixed 
  gneisses 
  ; 
  

   while 
  in 
  still 
  other 
  cases 
  the 
  Grenville 
  rocks 
  were 
  left 
  practically 
  

   intact 
  as 
  shown 
  by 
  the 
  large 
  areas 
  of 
  pure 
  Grenville. 
  

  

  95 
  

  

  