Titaniferous Andradite from Ontario. 



215 



Including "Water. 



(R 2 + CaO) 



Jan Mayen 3 



Bohemia 3 



Stenzelberg 3 



Dungannon 3 



(Mg, Mn, Fe)0. 

 3-87 

 4*10 

 4-02 

 3-84 



Excluding Water. 



(R 2 + CaO) : (Mg, Mn, Fe)0. 



3 : 4-17 



3 : 4-10 



3 : 4-38 



3 : 4-]i 



Scharizer adopts the foregoing ratios (3:1:3 and 3 : 4) as 



those of syntagmatite in calculating the composition of horn- 



i ir in 

 blendes intermediate between (R 2 R) 3 R 2 Si 3 12 and actinolite. 

 He assumes in the first place that all the alumina and ferric 

 oxide belong to the syntagmatite molecule (2). The sum of 

 the A1 2 3 and Fe 2 3 molecules (from the molecular ratio) mul- 

 tipled by three^ gives (Si0 2 )z on the one hand and (R 2 0-f- 

 EO)s on the other. The sum of (R 2 0+RO)z divided in the 

 proportion of 3:4 gives (R 2 O-f0aO)2 and MgO-f FeO)2. 

 Subtracting (MgO + FeO)s from the sum of the correspondin 

 molecules deduced from the analysis gives (MgO +FeO) a — that 

 is the number of molecules of magnesia and ferrous oxide 

 belonging to the actinolite molecule (A) — and (MgO-f-FeO)A 

 divided by three (see actinolite formula) gives the lime mole- 

 cules of the actinolite (CaO)A. This value subtracted from 

 the total number of lime molecules gives (CaO)s, and (CaO)s 

 subtracted from (R 2 0-f-CaO)s gives the alkali molecules (in 

 some cases including H 2 0). Finally (MgO-r-CaO)A gives 

 (Si0 2 )A. These statements will be made clearer by the follow- 

 ing example, one of those selected by Scharizer. 



Hornblende from Edexyille, analyzed by Rammelsberg. 



Original 

 analysis. 



Molee. R. 

 deduced 



from 

 analysis. 



Syntag- 

 matite. 



Actinolite. 



Calculated 

 composition. 



Original 



analysis 



calc. to 



100. 



Si0 2 51-67 



A1 2 3 .. 5-75 

 Fe 2 8 .. 2-86 

 MgO ... 23-37 

 CaO ... 12-42 

 Na 2 0... 0-75 

 K 2 0___. 0-84 

 H a O_... 0-46 



861 



5Q 



18 



584 



222 



12 



9 



25 



222 



56 i74 

 18 j ' 



127 ^| 



70 | 



12 ^222 



4J 



609 



457 



152 



51-97 

 5-99 

 3-00 



24-35 



12-96 



0-78 



0-88 



0-07 



52-66 

 5-86 

 2-91 

 23*82 

 12-66 

 0-78 

 9-86 

 0-47 



98*12 









100-00 



100-00 



