218 Adams and Ha? t rington — Alkali Hornblende, etc. 



Atomic. 



Si 610X4 = 



Ti. 13X4 = 



Al 192X3 = 



Fe m 200X3 = 



Fe TI 53X2 = 



Mn 18X2 = 



Ca 523X2 = 



Mff 35X2 = 



2492 2492 



Quantivalent. 

 2440 

 52 

 576 

 600 

 106 ^ 

 36 | 



io46 y U90 



70 I 



j- 11761 



V2466 



H 



32 



32 J 



The ratio for KO : K 2 8 : (SiTi)0 2 is 629 : 196 : 623, or, 

 calculating the titanium as Ti 3 3 , 629 : 203 : 610 = 3 : 1 : 3. 



The analysis therefore accords well with the ordinary garnet 



ii in 

 formula 3KO, R 2 0„ 3Si0 2 or K 3 K 2 Si 3 12 , and the mineral may 

 be regarded as a titaniferous andradite, with a considerable 

 proportion of the ferric oxide replaced by alumina. In com- 

 position it resembles somewhat the brown garnet from the 

 Island of Stoko, analyzed by Lindstrom.* 



By way of comparison the analysis of the Stoko garnet and 

 also one of a garnet from the nepheline-syenite of the Island 

 of Alnof are included in the following table. 



Stoko. Molec. R. 



Alno. Molec. R. 



Dungannon. Molec. R. 



Si0 2 36-63 610 610 



Ti0 2 .... 



A1 2 3 .-- 997 98 I 189 

 Fe 2 8 ... 13-45 84 j 1HZ 



FeO 2-28 32^) 



MnO -63 9 1 



CaO 35-90 641 [ rQQ 



MgO.... -28 7 f b98 



Na a O ... ... | 



Ign -16 9J 



31-15 519 ) ftn „ 

 6-73 84 \ 603 

 3-14 31 [ 



23 83 180 f 10U 



1 



•58 8 | 

 33-44 597 y 616 



•68 11 J 



36604 



1-078 



9-771 



15-996 

 3-852 

 1-301 



29-306 

 1-384 



"•285 



610 

 13 

 96 



100 

 53' 

 18 



523 

 35 



~ier 



• 623 



• 196 



► 645 



99-30 



99-55 



99-577 





*Zeitschr. fur Kiyst. u. Min., xvi, 160, 1890. 



f Sahlbom, in the paper by Hogbom already cited. 



