﻿70 
  Loughlin 
  and 
  Schaller 
  — 
  Crandallite, 
  a 
  New 
  Mineral. 
  

  

  these 
  plates 
  are 
  crushed 
  and 
  examined 
  microscopically 
  it 
  is 
  

   seen 
  that 
  they 
  are 
  composed 
  of 
  fibrous 
  aggregates, 
  the 
  fibers, 
  

   extremely 
  fine, 
  being 
  generally 
  in 
  radiated 
  groups. 
  The 
  con- 
  

   clusion 
  reached 
  is 
  that 
  crandallite 
  is 
  a 
  fibrous 
  mineral, 
  result- 
  

   ing 
  from 
  the 
  alteration 
  of 
  a 
  pre-existing 
  mineral 
  of 
  similar 
  

   chemical 
  composition 
  to 
  which 
  belong 
  the 
  platy 
  structure 
  and 
  

   smooth 
  cleavage 
  surface. 
  

  

  Description.— 
  The 
  exterior 
  surface 
  of 
  the 
  crandallite 
  lining, 
  

   which 
  is 
  about 
  a 
  millimeter 
  thick, 
  is 
  uneven 
  to 
  imperfect 
  

   botryoidal, 
  but 
  the 
  cross 
  sections 
  of 
  the 
  lining 
  show 
  a 
  distinct 
  

   straight 
  lamellar 
  structure, 
  the 
  individual 
  plates 
  being 
  about 
  a 
  

   fourth 
  of 
  a 
  millimeter 
  across 
  and 
  considerably 
  less 
  in 
  thickness. 
  

   The 
  part 
  of 
  the 
  lining 
  next 
  to 
  the 
  rock 
  is 
  compact 
  and 
  waxy 
  

   looking 
  whereas 
  the 
  last 
  formed 
  part 
  of 
  the 
  lining 
  seems 
  to 
  be 
  

   more 
  distinctly 
  and 
  coarsely 
  crystallized 
  and 
  somewhat 
  whiter 
  

   in 
  color. 
  When 
  crushed 
  and 
  examined 
  under 
  the 
  microscope, 
  

   however, 
  the 
  two 
  parts 
  appear 
  the 
  same 
  and 
  the 
  apparent 
  dif- 
  

   ferences 
  seen 
  in 
  the 
  hand 
  specimen 
  can 
  no 
  longer 
  be 
  noted. 
  

   The 
  crushed 
  fragments, 
  observed 
  under 
  the 
  microscope, 
  have 
  

   no 
  regular 
  boundaries 
  and 
  are 
  irregular 
  in 
  shape 
  with 
  only 
  a 
  

   faint 
  suggestion 
  of 
  the 
  lamellar 
  structure 
  seen 
  on 
  the 
  hand 
  

   specimen. 
  The 
  new 
  mineral 
  on 
  the 
  hand 
  specimen 
  closely 
  

   resembles 
  a 
  crust 
  of 
  very 
  fine-grained 
  dolomite 
  or 
  calcite 
  ; 
  in 
  

   thin 
  section 
  or 
  in 
  crushed 
  fragments, 
  with 
  nicols 
  crossed, 
  a 
  

   striking 
  resemblance 
  to 
  some 
  chalcedony 
  is 
  noted. 
  

  

  The 
  color 
  is 
  white 
  to 
  light 
  gray 
  with 
  shadings 
  into 
  yellow 
  

   and 
  brown. 
  The 
  streak 
  is 
  white. 
  The 
  luster 
  is 
  dull, 
  some- 
  

   what 
  greasy 
  in 
  the 
  more 
  compact, 
  and 
  somewhat 
  pearly 
  in 
  the 
  

   coarser 
  lamellar 
  variety. 
  Almost 
  opaque 
  on 
  the 
  hand 
  speci- 
  

   men, 
  the 
  crushed 
  fragments 
  are 
  transparent 
  to 
  opaque 
  under 
  

   the 
  microscope, 
  the 
  opacity 
  being 
  caused 
  by 
  minute 
  indeter- 
  

   minate 
  inclusions, 
  many 
  of 
  them 
  apparently 
  unreplaced 
  ore 
  

   minerals. 
  The 
  mineral, 
  free 
  from 
  any 
  inclusions, 
  is 
  colorless 
  

   and 
  transparent 
  in 
  thin 
  pieces. 
  The 
  cleavage 
  on 
  the 
  hand 
  

   specimen 
  is 
  distinct 
  and 
  the 
  cleavage 
  faces 
  have 
  a 
  decidedly 
  

   pearly 
  luster. 
  The 
  direction 
  of 
  the 
  cleavage 
  is 
  basal, 
  such 
  

   fragments, 
  which 
  are 
  unaltered, 
  being 
  isotropic 
  and 
  yielding 
  

   a 
  uniaxial 
  positive 
  interference 
  figure. 
  This 
  basal 
  cleavage 
  is 
  

   believed 
  to 
  be 
  the 
  cleavage 
  of 
  the 
  original 
  mineral 
  (goyazite 
  ?), 
  

   whose 
  alteration 
  has 
  yielded 
  crandallite. 
  The 
  cleavage 
  of 
  

   crandallite 
  could 
  not 
  be 
  determined. 
  The 
  density 
  was 
  not 
  

   determined, 
  on 
  account 
  of 
  the 
  scarcity 
  of 
  the 
  material 
  and 
  

   because 
  of 
  the 
  many 
  impurities. 
  The 
  brittle 
  mineral 
  has 
  a 
  

   hardness 
  of 
  about 
  4. 
  

  

  Optical 
  properties. 
  — 
  The 
  white 
  or 
  gray 
  crandallite 
  is 
  color- 
  

   less 
  and 
  non-pleochroic 
  under 
  the 
  microscope. 
  The 
  material 
  

   analyzed 
  contained 
  a 
  considerable 
  amount 
  of 
  impurities, 
  chiefly 
  

   quartz, 
  with 
  a 
  little 
  barite 
  and 
  traces 
  of 
  sulphides. 
  The 
  

  

  