﻿270 
  Phillips 
  — 
  Mineralogical 
  StrucUire 
  and 
  Chemical 
  

  

  shales, 
  but 
  breaks 
  up 
  through 
  them, 
  its 
  surface 
  area 
  becoming 
  

   very 
  much 
  narrowed 
  in 
  couseqiieuce. 
  

  

  At 
  several 
  points 
  in 
  the 
  fused 
  shales 
  well 
  crystallized 
  epidote 
  

   and 
  tourmaline 
  have 
  been 
  found, 
  and 
  especially 
  at 
  the 
  Griggs- 
  

   town 
  copper 
  mine, 
  where 
  very 
  perfect 
  crystals 
  of 
  black 
  tour- 
  

   maline 
  completely 
  fill 
  some 
  specimens 
  of 
  the 
  shale. 
  They 
  are 
  

   hemimorphic, 
  showing 
  the 
  hexagonal 
  prism 
  with 
  fine 
  longi- 
  

   tudinal 
  striatiqns, 
  terminated 
  at 
  one 
  end 
  by 
  the 
  rhombohedra 
  

   (0221) 
  and 
  (1011), 
  the 
  antilogous 
  pole 
  being 
  more 
  complicated. 
  

   Here 
  also 
  amygdaloid 
  cavities 
  were 
  found, 
  one 
  of 
  which 
  w^as 
  

   1-3 
  inches 
  in 
  length, 
  with 
  walls 
  thickly 
  studded 
  with 
  well- 
  

   formed 
  crystals 
  of 
  epidote, 
  calcite 
  and 
  a 
  yellow 
  mica, 
  probably 
  

   chalcodite. 
  

  

  Macroscopic 
  Description. 
  

  

  At 
  the 
  village 
  of 
  Rocky 
  Hill, 
  the 
  Millstone 
  River 
  cuts 
  

   through 
  the 
  trap 
  ridge 
  at 
  nearly 
  a 
  right 
  angle, 
  forming 
  a 
  gorge 
  

   150 
  feet 
  deep 
  ; 
  along 
  the 
  eastern 
  side 
  of 
  this 
  gorge 
  the 
  Rock}^ 
  

   Hill 
  Stone 
  Storage 
  Company 
  has 
  opened 
  three 
  quarries, 
  located 
  

   in 
  different 
  positions 
  of 
  the 
  dike, 
  as 
  related 
  to 
  a 
  vertical 
  cross- 
  

   section. 
  No. 
  1 
  is 
  near 
  the 
  lower 
  side, 
  480 
  feet 
  from 
  the 
  con- 
  

   tact 
  border; 
  JN'o. 
  2 
  is 
  near 
  the 
  middle 
  of 
  the 
  dike, 
  1350 
  feet 
  

   from 
  No. 
  1, 
  and 
  No. 
  3 
  420 
  feet 
  from 
  the 
  upper 
  contact 
  and 
  

   1600 
  feet 
  from 
  No. 
  2. 
  These 
  distances 
  are 
  only 
  approximate, 
  

   as 
  the 
  upper 
  and 
  lower 
  contacts 
  cannot 
  be 
  made 
  out 
  definitely. 
  

   Quarry 
  No. 
  2 
  is 
  the 
  only 
  one 
  woi-ked 
  at 
  present, 
  rock 
  being- 
  

   taken 
  out 
  and 
  crushed 
  for 
  road 
  and 
  ballasting 
  purposes. 
  Each 
  

   of 
  these 
  three 
  quarries 
  represents 
  a 
  different 
  phase 
  of 
  the 
  rock, 
  

   not 
  only 
  in 
  macroscopical 
  appearance, 
  but 
  also 
  in 
  the 
  chemical 
  

   composition 
  of 
  the 
  mineral 
  constituents, 
  as 
  well 
  as 
  in 
  the 
  

   analyses 
  of 
  the 
  rock 
  as 
  a 
  whole. 
  

  

  Specimens 
  near 
  the 
  contact 
  with 
  the 
  shale 
  have 
  a 
  very 
  fine, 
  

   granular, 
  almost 
  massive 
  structure, 
  appearing 
  to 
  the 
  eye 
  homo- 
  

   geneons, 
  except 
  here 
  and 
  there, 
  where 
  light 
  is 
  i-eflected 
  from 
  

   an 
  almost 
  microscopical 
  cleavage 
  face 
  of 
  a 
  feldspar 
  crystal; 
  

   otherwise 
  the 
  boundary 
  rock, 
  and 
  especially 
  on 
  the 
  lower 
  side, 
  

   is 
  a 
  dark, 
  slate-blue 
  color, 
  massive 
  and 
  compact, 
  showing 
  no 
  

   cavities 
  or 
  schistose 
  structure. 
  Passing 
  in 
  from 
  the 
  crypto- 
  

   crystalline 
  border 
  region, 
  when 
  quarry 
  No. 
  1 
  is 
  reached, 
  the 
  

   rock 
  has 
  assumed 
  the 
  characteristic 
  textnre 
  of 
  an 
  ordinary 
  

   dolerite 
  ; 
  here 
  it 
  presents 
  a 
  coarse-granular 
  appearance, 
  in 
  

   which 
  its 
  two 
  prominent 
  minerals, 
  feldspar 
  and 
  augite, 
  are 
  

   easily 
  distinguished; 
  as 
  the 
  aggregation 
  of 
  feldspar 
  crystals 
  

   proceeds, 
  the 
  color 
  of 
  the 
  rock 
  is 
  less 
  dark, 
  and 
  specimens 
  from 
  

   quarry 
  No. 
  2 
  appear 
  much 
  lighter 
  than 
  any 
  others. 
  Here 
  the 
  

   augite 
  crystals 
  reach 
  a 
  length 
  of 
  f 
  of 
  an 
  inch. 
  In 
  this 
  region 
  

   there 
  is 
  a 
  well-defined 
  schistosity 
  developed, 
  produced 
  by 
  the 
  

  

  