﻿350 
  Penfield 
  and 
  Warren 
  — 
  Minerals 
  from 
  FranTdin^ 
  N. 
  J, 
  

  

  Two 
  molecules 
  of 
  

  

  Intermediate 
  or 
  

  

  orthosilicic 
  acid. 
  

  

  mesosilicic 
  acid. 
  

  

  HO 
  

  

  HO 
  

  

  Ho:>., 
  

  

  H0>^' 
  

  

  HO^^. 
  

   H0>^^ 
  

  

  

  °< 
  

  

  

  s^^i 
  

  

  HO^ 
  

  

  HO^ 
  

  

  The 
  intermediate 
  acid 
  H^Si^O^ 
  is 
  one 
  which 
  lias 
  been 
  recog- 
  

   nized 
  by 
  mineralogists, 
  but 
  its 
  salts 
  have 
  not 
  generally 
  received 
  

   a 
  prominent 
  place 
  in 
  the 
  systematic 
  classifications 
  of 
  silicates, 
  

   because 
  they 
  are 
  not 
  very 
  numerous. 
  Groth^ 
  calls 
  attention 
  to 
  

   the 
  acid 
  and 
  its 
  salts, 
  and 
  has 
  given 
  the 
  name 
  " 
  Diorthokiesel- 
  

   sdure^^ 
  to 
  the 
  acid. 
  Clarke 
  f 
  also 
  has 
  discussed 
  the 
  chemical 
  

   relations 
  of 
  the 
  minerals 
  of 
  this 
  group, 
  adopting 
  Groth's 
  name 
  

   diorthosilicic 
  acid^ 
  and 
  calling 
  the 
  minerals 
  diorthosilicates. 
  

   The 
  name 
  diorthosilicic 
  seems, 
  however, 
  inappropriate, 
  since 
  

   HgSigO^ 
  is 
  not 
  an 
  orthosilicic 
  acid 
  as 
  the 
  name 
  signifies, 
  but 
  a 
  

   derivative 
  of 
  orthosilicic 
  acid. 
  We 
  feel, 
  therefore, 
  warranted 
  

   in 
  suggesting 
  new 
  names, 
  mesosilicic 
  for 
  the 
  acid 
  and 
  mesosili- 
  

   cates 
  for 
  its 
  salts, 
  the 
  prefix 
  meso 
  being 
  derived 
  from 
  fieao^;, 
  

   signifying 
  middle 
  or 
  between. 
  The 
  intermediate 
  relation 
  of 
  

   mesosilicic 
  acid 
  is 
  evident 
  from 
  the 
  following 
  : 
  

  

  Orthosilicic 
  acid, 
  two 
  molecules, 
  HgSi^Og. 
  

   Mesosilicic 
  acid, 
  H^Si^O.. 
  

  

  Metasilicic 
  acid, 
  two 
  molecules, 
  H^Si^Og. 
  

  

  The 
  mesosilicates 
  are 
  classed 
  by 
  Dana 
  in 
  the 
  small 
  group 
  of 
  

   " 
  Intermediate 
  Silicates 
  " 
  on 
  page 
  416 
  of 
  his 
  Mineralogy, 
  and 
  

   by 
  Groth 
  as 
  " 
  Interniedi'dre 
  hilikate 
  " 
  on 
  page 
  138 
  of 
  his 
  

   TJebersicht 
  der 
  Miner 
  alien. 
  

  

  The 
  commonest 
  mesosilicate 
  is 
  iolite, 
  the 
  composition 
  of 
  

   which 
  may 
  be 
  expressed 
  as 
  a 
  slightly 
  basic 
  salt, 
  as 
  follows 
  : 
  

   (Mg, 
  Fe),Al„{Al. 
  OH),(Si,0,)„ 
  although 
  the 
  two 
  hydroxyls 
  

   may 
  be 
  in 
  combination 
  with 
  the 
  bivalent 
  metals 
  instead 
  of 
  

   with 
  the 
  aluminium. 
  One 
  of 
  the 
  few 
  lead 
  silicates, 
  barysilite, 
  

   PbgSi^O,, 
  is 
  a 
  normal 
  salt 
  of 
  mesosilicic 
  acid, 
  as 
  is 
  also 
  the 
  

   Franklin 
  mineral 
  hardystonite, 
  Ca^ZuSi^O,, 
  recently 
  described 
  

   by 
  Wolff.J 
  Hardystonite 
  is 
  said 
  to 
  occur 
  at 
  the 
  Parker 
  shaft, 
  

   North 
  Mine 
  Hill, 
  but 
  we 
  have 
  not 
  yet 
  observed 
  it 
  associated 
  

   with 
  any 
  of 
  the 
  new 
  minerals 
  described 
  in 
  the 
  present 
  paper. 
  

  

  * 
  Tabellarische 
  TJebersicht 
  der 
  Mineralien, 
  IV 
  Auflage, 
  pp. 
  105 
  and 
  140. 
  

   t 
  Constitution 
  of 
  the 
  silicates; 
  Bull, 
  of 
  U. 
  S. 
  Geolog. 
  Survey, 
  No. 
  125, 
  p. 
  81. 
  

   % 
  Proceedings 
  of 
  the 
  Am. 
  Acad, 
  of 
  Arts 
  and 
  Sci., 
  xxxiv, 
  p. 
  479, 
  1899. 
  

  

  