﻿58 
  TWENTY-FIRST 
  REPORT 
  ON 
  THE 
  STATE 
  CABINET, 
  

  

  evidently 
  from 
  a 
  clrusy 
  cavity, 
  such 
  as 
  those 
  often 
  met 
  with, 
  rep* 
  

   resenting 
  unfilled 
  spaces 
  in 
  the 
  midst 
  of 
  the 
  veins, 
  and 
  lined 
  with 
  

   large 
  and 
  well-defined 
  prisms 
  of 
  apatite 
  or 
  of 
  pyroxene. 
  

  

  While 
  these 
  associations 
  evidently 
  show 
  a 
  successive 
  deposition 
  

   of 
  the 
  various 
  mineral 
  species, 
  another 
  phenomenon, 
  sometimes 
  

   observed 
  in 
  vein-crystals, 
  is 
  presented 
  by 
  a 
  prism 
  of 
  yellow 
  

   idocrase 
  from 
  a 
  veinstone 
  of 
  orthoclase 
  and 
  pyroxene 
  in 
  Grenville, 
  

   Quebec. 
  One 
  extremity 
  of 
  the 
  prism, 
  which 
  is 
  about 
  half 
  an 
  inch 
  

   in 
  diameter, 
  is 
  imbedded 
  in 
  the 
  matrix 
  of 
  the 
  two 
  minerals 
  just 
  

   named, 
  while 
  the 
  other, 
  being 
  broken 
  across, 
  shows 
  that 
  the 
  

   idocrase 
  forms 
  but 
  a 
  thin 
  incrusting 
  shell, 
  and 
  is 
  filled 
  with 
  a 
  con- 
  

   fused 
  crystalline 
  aggregrate 
  of 
  orthoclase, 
  holding 
  a 
  small 
  prism 
  

   pf 
  zircon. 
  This 
  would 
  show 
  that 
  a 
  skeleton-crystal, 
  such 
  as 
  is 
  

   sometimes 
  seen 
  in 
  crystallizing 
  solutions, 
  had 
  at 
  first 
  formed, 
  and 
  

   was 
  subsequently 
  filled 
  up 
  with 
  the 
  other 
  minerals. 
  Similar 
  cases 
  

   are 
  well 
  known 
  to 
  mineralogists 
  ; 
  thus 
  the 
  crystals 
  of 
  zircon 
  from 
  

   Laurentian 
  veins 
  in 
  St. 
  Lawrence 
  county, 
  New 
  York, 
  are 
  some- 
  

   times 
  filled 
  with 
  calcareous 
  spar 
  ; 
  and 
  a 
  granitic 
  vein 
  at 
  Had 
  dam, 
  

   Connecticut, 
  has 
  afforded 
  prisms 
  of 
  beryl 
  filled 
  with 
  a 
  mixture 
  

   of 
  orthoclase 
  and 
  quartz 
  holding 
  minute 
  crystals 
  of 
  garnet 
  and 
  

   of 
  tourmaline. 
  A 
  strong 
  confirmation 
  of 
  the 
  view 
  that 
  these 
  

   minerals 
  have 
  been 
  deposited 
  in 
  their 
  veins 
  from 
  solution, 
  is 
  

   afforded 
  by 
  certain 
  phenomena 
  not 
  hitherto 
  explained, 
  which 
  

   were, 
  I 
  believe, 
  first 
  noticed 
  by 
  the 
  late 
  Dr. 
  Emmons. 
  He 
  ob- 
  

   served 
  that 
  crystals 
  of 
  quartz 
  imbedded 
  in 
  crystalline 
  limestone, 
  

   in 
  Eossie, 
  New 
  York, 
  have 
  their 
  angles 
  so 
  much 
  rounded 
  that 
  

   the 
  prismatic 
  form 
  is 
  almost 
  or 
  entirely 
  effaced, 
  the 
  surfaces 
  

   being 
  smooth 
  and 
  shining. 
  This 
  appearance, 
  although 
  not 
  con- 
  

   stant, 
  is 
  observed 
  in 
  many 
  localities, 
  and 
  is 
  not 
  confined 
  to 
  quartz 
  

   alone 
  — 
  crystals 
  of 
  apatite 
  and 
  of 
  carbonate 
  of 
  lime 
  sometimes 
  

   exhibiting 
  the 
  same 
  peculiarity. 
  At 
  the 
  same 
  time 
  as 
  remarked 
  

   by 
  Dr. 
  Emmons, 
  the 
  feldspar, 
  scapolite, 
  pyroxene, 
  zircon 
  and 
  

   sphene 
  of 
  these 
  limestones 
  present 
  perfect 
  forms, 
  the 
  crystals 
  of 
  

   orthoclase, 
  even 
  in 
  contact 
  with 
  the 
  rounded 
  crystals 
  of 
  quartz, 
  

   retaining 
  their 
  sharpness 
  of 
  outline. 
  Dr. 
  Emmons 
  considered 
  the 
  

   rounded 
  angles 
  of 
  these 
  cyrstals 
  to 
  be 
  due 
  to 
  a 
  partial 
  fusion, 
  

   though 
  at 
  the 
  same 
  time 
  he 
  did 
  not 
  overlook 
  the 
  fact 
  that 
  the 
  

   quartz, 
  apatite 
  and 
  calcite 
  were 
  less 
  fusible 
  than 
  those 
  species 
  

   which, 
  under 
  similar 
  circumstances, 
  retained 
  their 
  crystalline 
  forms 
  

   intact 
  {Geology 
  of 
  the 
  First 
  District 
  of 
  New 
  York, 
  pages 
  57, 
  58). 
  

  

  These 
  observations 
  have 
  since 
  been 
  abundantly 
  confirmed 
  in 
  

  

  