﻿Loughlin 
  and 
  Schaller 
  — 
  Crandallite, 
  a 
  New 
  Mineral. 
  71 
  

  

  crandallite 
  was 
  in 
  irregular 
  granular 
  or 
  cryptocrystalline 
  

   masses, 
  many 
  of 
  which 
  showed 
  distinctly 
  on 
  high 
  magnifica- 
  

   tion 
  a 
  fibrous 
  structure 
  in 
  large 
  part 
  radiating. 
  The 
  individual 
  

   fibers 
  are 
  very 
  minute 
  and 
  it 
  was 
  not 
  possible 
  to 
  isolate 
  on 
  the 
  

   glass 
  slide 
  a 
  fragment 
  or 
  fiber 
  which 
  was 
  composed 
  of 
  only 
  one 
  

   unit. 
  The 
  refractive 
  indices 
  of 
  the 
  mineral 
  showed 
  a 
  minimum 
  

   of 
  1*585 
  and 
  a 
  maximum 
  of 
  1*595, 
  the 
  birefringence 
  of 
  the 
  

   material 
  ranging 
  from 
  zero 
  to 
  a 
  maximum 
  of 
  about 
  0*01. 
  

   Some 
  of 
  the 
  material 
  appears 
  amorphous, 
  but 
  it 
  may 
  be 
  very 
  

  

  Fig. 
  1. 
  

  

  Fig. 
  2. 
  

  

  Fig. 
  1. 
  A 
  portion 
  of 
  a 
  hexagonal 
  crystal, 
  basal 
  section, 
  showing 
  concen- 
  

   tric, 
  radiating 
  fibrous 
  structure. 
  A 
  pseudomorph 
  of 
  crandallite 
  (fibrous) 
  

   after 
  goyazite 
  (?). 
  

  

  Fig. 
  2. 
  A 
  crystal 
  plate 
  showing 
  fibrous 
  structure, 
  and 
  with 
  a 
  birefracting 
  

   center 
  with 
  isotropic 
  rim. 
  A 
  pseudomorph 
  of 
  crandallite 
  (fibrous) 
  after 
  

   goyazite 
  (?). 
  

  

  finely 
  cryptocrystalline. 
  The 
  fibers 
  apparently 
  have 
  parallel 
  

   extinction 
  and 
  the 
  elongation 
  is 
  negative. 
  

  

  Some 
  of 
  the 
  crandallite 
  on 
  the 
  hand 
  specimen 
  which 
  

   appeared 
  better 
  crystallized 
  than 
  the 
  material 
  analyzed, 
  was 
  

   crushed 
  and 
  examined 
  optically. 
  In 
  this 
  crushed 
  material 
  were 
  

   found 
  several 
  irregularly 
  shaped 
  to 
  poorly 
  defined 
  hexagonal 
  

   plates 
  which 
  were 
  isotropic, 
  uniaxial, 
  positive, 
  and 
  which 
  on 
  

   edge 
  gave 
  parallel 
  extinction 
  and 
  a 
  moderate 
  birefringence 
  

   (estimated 
  as 
  about 
  0*01-0*02). 
  The 
  refractive 
  index 
  varied 
  

   from 
  about 
  l*605dr*005 
  to 
  1*62. 
  Some 
  of 
  these 
  plates 
  were 
  

   uniform 
  in 
  structure 
  and 
  isotropic 
  ; 
  others 
  showed 
  a 
  concen- 
  

   tric, 
  radiating, 
  fibrous 
  structure 
  (fig. 
  1), 
  and 
  were 
  either 
  iso- 
  

   tropic 
  (index 
  about 
  l*605=fc*005) 
  or 
  else 
  feebly 
  birefracting. 
  

   A 
  single 
  crystal 
  plate 
  showed 
  an 
  inside 
  area 
  which 
  was 
  feebly 
  

   birefracting, 
  the 
  fibers 
  giving 
  parallel 
  extinction 
  while 
  the 
  out- 
  

   side 
  rim 
  was 
  isotropic, 
  although 
  both 
  parts 
  showed 
  a 
  distinct 
  

   fibrous 
  structure 
  as 
  shown 
  in 
  fig. 
  2. 
  

  

  