276 On the Classification of the Silicates and their allied Compounds. 



Wernerite Type : — Dimetric. 



Gehlenite, 3(3RO, Si 3 ) + 3R 2 3 , SiO 3 ; humboldtilite, 

 2(3RO, Si O 3 ) + R 2 O 3 , Si 3 ; dipyre, 4(RO, SiO 3 ) + 3(A1 2 3 , 

 Si O 3 ) ; meionite, 3CaO, Si O 3 + 2(A1 2 O 3 , Si O 3 ) ; wernerite, 

 3CaO, Si0 3 + 3(Al 2 3 ,Si0 3 ); scapolite, 3RO,2Si0 3 + 2(Al 2 3 , 

 SiO 3 ). The three latter formula? afford another proof of the 

 insufficiency of our present chemical system in its applications to 

 mineralogy ; unless, indeed, it be admitted that chemical and 

 physical phamoniena have no relations to each other — an idea 

 the mind refuses to receive. 



Palagonite may perhaps be attached to this type as a kind of 

 scapolite-obsidian. 



Leucite Type : — Monometric. 



Leucite, 3KO, 2Si0 3 + 3(Al 2 3 , 2Si0 3 ) ; analcime, 3NaO, 

 2Si0 3 + 3(Al 2 3 , 2Si0 3 ) + 6H 2 = leucite + 6H 2 0; glotta- 

 lite, 3CaO, 2Si0 3 + Al 2 3 , Si0 3 + 9H 2 0. 



Lapis-Lazuli Type : — Monometric. 

 Lapis-lazuli; haiiyne, 3(NaO, KO), SiO 3 + 3(A1 2 3 , SiO 3 ) 

 -f 2(CaO, SO 3 ); nosean, 3NaO, SiO 3 + 3(A1 2 3 , Si0 3 ) + NaO, 

 SO 3 ; skolopsite, 3(3RO, 2Si0 3 ) + 3(A1 2 3 , SiO 3 ) + NaO, SO 3 ; 

 ittnerite [3RO, SiO 3 + 3(A1 2 3 , SiO 3 ) + 6H 2 0] + CaO, SO 3 

 and NaCl; sodalite, 3NaO, Si0 3 + 3(A1 2 3 , Si0 3 )+NaCl. 



Nepheline Type : — Hexagonal. 



Davyne, cancrinite, 2RO, Si0 3 + 2(A1 2 3 , Si0 3 )+RO,C0 2 

 + H 2 ; stroganowite, formula like the preceding but without 

 the water ; nepheline, 2RO, Si 3 + 2(Al 2 O 3 , Si O 3 ) ; chabasite, 

 3RO, 2Si0 3 + 3(Al 2 3 , 2Si0 3 ) + 18H 2 0, also (herschellite, etc.) 

 the same - 3H 2 0, and (other varieties) RO, Si0 3 + Al 2 3 , 

 2Si0 3 + 6H 2 0. Chabasite and its allied forms might perhaps 

 with greater propriety be arranged as a separate type. 



Apophyllite Type : — Dimetric. 

 Apophyllite[8(CaO, Si0 3 ) + KO, 2Si0 3 + 16H 2 0] +*CaF(?); 

 faujasite, 3RO, 4Si0 3 + 3(A1 2 3 , 2Si0 3 ) + 24di 2 0; zeagonite, 

 2RO, Si0 3 + 2(A1 2 3 , Si0 3 )+9H 2 0; edingtonite (?). 



Desmine (Stilbite) Type : — Trimetric. 

 Prehnite, 2CaO, Si O 3 + Al 2 3 , Si O 3 + H 2 ; thomsonite, 

 3RO, Si O 3 + 3(A1 2 O 3 , Si O 3 ) + 7H 2 j phillipsite, 3RO, 2Si0 3 

 + 4(A1 2 3 , 2Si0 3 ) + 18H 2 0; harmatome, 3BaO, 2Si0 3 + 

 4(A1 2 O 3 , 2Si0 3 ) + 18H 2 O ; natrolite (mesotype), Na O, SiO 3 

 + A1 2 3 , SiO 3 + 2H 2 0; scolezite (? monoclinic), RO, SiO 3 

 + A1 2 3 , Si0 3 + 3H 2 0; desmine (stilbite), CaO, Si0 3 + Al 2 3 , 



