Chemical Composition of Amphibole. 



35 



due to the Director of the Survey for permission to use the 

 material in any way for scientific purposes. The habit of the 

 crystals is unusual and is shown by figure 2, but, the crystals 

 being attached, doubly terminated ones have not been observed. 

 Figure 3 represents one end of a twin crystal. The forms 

 which are quite numerous for amphibole are : a (100), o (010), 

 o (001), n (310), m (110), e (130) r (011), i (031), t (101) and 

 o ^121). It was through! that perhaps the unusual develop- 

 ment of these crystals might be due to some peculiarity in 

 chemical composition, but the results of the analysis have not 

 borne out this supposition. The color of the crystals is a dark 

 greenish-black. The powder used for analysis floated at 3'115 

 and sank at 3*107, the mean specific gravity being 3 - lll. 















Per cents of 





I 



II 



Average 



Eatios 



protoxide 



bases 



SiO„ 

 Ti0 o 



52-58 

 •25 



52-05 



52-31 



•28 



•872 ) 

 •004 [ " 8 < 6 







A1A 



2-72 



2-66 



2-69 



'° 26 ' "045 

 •019 \ U45 







Fe 2 3 



3-32 



2-85 



3-09 







FeO 



6-83 



6-53 



6-68 



•093' 





10-1 



) 



MnO 



•70 







•70 



•010 





1-1 



.83-8 



MoO 



19-12 



19-42 



19-27 



•482 





52-6 



) 



CaO 



11-88 



11-88 



11-88 



" -212 





23-1 



) 



K 2 



•50 







•50 



•005 }>-9l7 



•6 



>-25-0 



Na„0 



•78 







•78 



•012 j 



1-3 



I 



H,0 



1-55 



1-45 



1-42 



•079 j 



8-6 





f; 



•93 

 110° 





•93 



•08 



•024 J 



2-6 





Loss at 



ioo-o 







100-59 









= F 2 



•39 











100-20 



Discussion of the Tremolite and Actinolite Analyses : — 

 Since tremolite and actinolite constitute a group by them- 

 selves, differing somewhat in molecular ratios from other 

 varieties containing high percentages of sesquioxides (A1 2 3 

 and Fe 2 3 ) which will be considered later, it seems best at this 

 point to discuss the analyses already described. Attention 

 may first be called to the ratio of Si0 2 to the protoxide bases 

 R^O, the latter including K 2 0, Na a O, H 2 and F 2 . The 

 ratios are as follows : — 



