48 



Penfield and Stanley- 



la this analysis it will be noted that with a large R 2 3 quo- 

 tient the ratio of Si0 2 : RO = '687 : 694 = 1-00 : 1-01, or almost 

 exactly 1 : 1, thus differing from analysis VII to X (summa- 

 rized on page 42), all of which showed an excess of RO. It is- 

 also interesting to note that the ratio of this hornblende is like 

 that of garnet ; Si0 2 : R 2 3 : RO being 3'00 : 0-95 : 3-03, a very 

 close approximation to 3 : 1 : 3. 



In the interpretation of the analysis there may be assumed, 

 in addition to the alumo-hydroxyl radical, one similar to that 

 used in analysis X, [A1 2 3 R], except that in this case it is pro- 

 posed to double the radical and make one R equal (Fe,Mg) the 

 other Na 2 plus a little Ca ; or, since there is practically no 

 fluorine in the mineral, the water may be regarded as basic 

 and only one radical need be used. The results in detail, 

 regarding (OH) as combined with alumina, are as follows : 



"Al— OH~| " 

 Eatios ^O Residue 



Al 



[Si,Ti]0„ 



[Al,-Fe],0, 



[Fe,Mg]0 



CaO 



[K,Na] o 



f; 



•687 

 •218 

 •385 

 •213 

 •072 

 -.023 

 •001 



-OIIJ 



-•024 

 — •024 



•024 



663 



194 



385 

 213 ) 

 072 f 



[A1„0 



;ai 2 o 



,(Fe,M ff )]" 



3 (Na 2 ,Ca)]" : 



3esidu 





—•194 

 —•194 



—•097 



—•097 



•469 



•288 

 •188 





Total RO = 



•476 



Or disregarding the small amount of fluorine present and con- 

 sidering all the water as basic, only the second radical need be 

 used, as follows : 



[Si,Ti]O s 



[Al,Fe] 2 () 3 



[Fe,Mg]0 



CaO 



[K,Na],0 



HO 



Total RO= -475 



Proportion of radicals and remaining bases, I regarding (OH) 

 as combined with Al, II regarding water as basic : 

 Ratios I Per cents I Ratios II 

 •024 3-4 _!__ 

 •194 28-0 '218 

 •288 41-5 -276 

 •1SS 27-1 -176 

 -023 





[Al 9 0,(Fe,Mg)]" 





Ratios 



jAl 2 B (Na 2 ,C 



»)]" 



Residue 



•687 



—•218 





•469 



•218 



— -218 









•385 



—•109 





• -276 



•213 1 



•072 \ 



—•109 





•176 



•023 







•023 



[Al o 0(0H) o ]"0 



[A1 2 3 R]"(3 



[Fe,Mg]0 



CaO 



HO 



Per cents II 



31-5 



39-8 



25-4 



3-3 



•694 



100-0 



•692 



100-0 



