280 Dr, J. E. Reynolds on certain Mineral Silicates. 



\Si/ 



Sarcolite (Ki&Ca"+^NaS) 8 +*£l) a X 06 



/0«\ 



Paranthite . . (|Ca' ,3 +|Al 2 )>\0 6 



/0 6 \ 



Auorthite . . (iCa //3 +|Ai)V<0 6 



/0»\ 



Class 3. xSiV 



Leucite .... (iK e +|Al) 2 Vo 6 



Andcsite . (i(Ca'W) 8 +£Al) a X° 6 



/0 la \ 



sSiV 



Hyalophane (£(Ba" f K^+f^X 06 



/0 la \ 



\SiV 



Oligoclase . (;KCa"Na 2 ) 3 +fAl 2 X° 6 



Class 4. 



Albite .... (^Na^lAl^^Xo 6 



/o 18 \ 



Ortlioclase . . (iK B +|Al) 2 X° 6 



As these lists of minerals are only intended to illustrate the 

 application of the principle of classification proposed in this 

 paper, I have carefully avoided entering upon doubtful questions 

 by expressing the constitution of silicates which have been hi- 

 therto insufficiently examined. 



The above arrangement of the formulae renders remarkably 

 evident the relations existing between the members of the felspar 

 and other families. This group of minerals illustrates the mode 

 of accumulation of the anhydride SiO 6 ' upon itself without other- 

 wise disturbing the arrangement of the molecule; and the com- 

 position of these silicates appears to me forcibly to testify that 

 the normal rate of condensation of the molecule of SiO 2 is three, or 

 some simple multiple of that number. 



It is a well-known fact that anorthite and leucite are two im- 



