clarke.] FELDSPARS AND SCAPOLITES. 29 
muscovite, or pinite, which is only an impure pseudoinorphous mica; 
and kaolin, crystallographically, has close relations with the mica 
family. Feldspars, scapolites, muscovite, and kaolin are therefore 
presumably connected, and the structural formulae of the minerals 
should render the relationship apparent. 
The empirical formulae to be considered are now as follows : 
Albite AlKaSigOa 
Anorthite Al 2 CaSi 2 8 
Meionite A] fi Ca 4 Si (j 025 
Marialite Al 3 Na 4 Si 9 24 Cl 
Muscovite Al 3 KH 2 Si 3 12 
Kaolin Al 2 H 4 Si 2 9 
For muscovite the constitution has already been indicated; and this 
clew, together with the general hypothesis of derivation from normal 
salts, enables us to correlate all six of the formulae given. To do this 
it is necessary to triple the formulae of albite and anorthite, and we 
have the following expressions : 
Albite. Anorthite. 
.Si 3 8 =jS"a 3 .SiO.EAl 
Al— Si 3 8 =Al Al— Si0 4 BAl 
\si 3 8 =Al \si0 4 =rCa 
I 
Ca 
I 
.Si0 4 -=Ca 
Al— Si0 4 =Al 
\si0 4 =Al 
Marialite. Meionite. 
Si 3 8 =Na 2 .SiG 4 =Al 
Al^Si 3 G 8 =Na7 C1 Al-SiG 4 -Al 
\si 3 8= Al ^Si0 4= Ca 
Oa 
I 
O 
I 
Ca 
I 
,Si0 4 =Oa 
Al— Si0 4 ZAl 
\si0 4 =Al 
Muscovite. Kaolin. 
.Si0 4 ^KH 2 .OH 
Al— Si0 4 ZEAI Al— SiO, TT 3 
\Si04=Al \siG 4 -Al 
