Palache.] 



New Soda Amphibole, 



From the atomic ratios found in the last column the following 

 formula is derived: — 



Na.Al.^SiiO,., — Glaucophane molecule. 



2[Na 2 FejSi 4 Oi 2 ] — Riebeckite molecule. 



9[RSi0 3 ] — Actinolite molecule, 

 where R = Mg : Fe : Ca = 6 : 2 : l 



In this formula the ratio of Fe to Fe is made 4:2 instead of 

 3 : 3, as found in the analysis, and Mg is taken as 6 instead of 5. 



In the following table are presented typical analyses of glauco- 

 phane and of riebeckite, together with the analysis of the Berkeley 

 mineral : — 









Berkeley 





Glaucophane.* 



Riebeckite.! 



Amphibole. 



SiCX 



55.64 



5O.OI 



55.02 



A1.A 



15. 1 I 





4-75 



Fe 2 3 



3.08 



28.30 



10.91 



FeO 



6.85 



9.87 



9-45 



MnO 



•56 



•63 



trace 



MgO 



/.80 



■34 



9-30 



CaO 



2.40 



1.32 



2.38 



Na.,0 



9-34 



8.79 



7.62 



K,0 







•27 





100.78 



99.98 



99.70 



Classification. — Comparing these analyses we see that the Berke- 

 ley mineral occupies a mean position between the other two, having 

 less alumina than glaucophane, less iron than the riebeckite, and 

 more of the monoxide bases than either. This relation is well 

 expressed in the formula given above, in which we see that the 

 sesquioxide bases are divided between one glaucophane and two 

 riebeckite molecules, and the abundant monoxide bases appear in 

 a proportion of the actinolite molecule larger than is normal for 

 either glaucophane or riebeckite. 



It thus appears that we have in this mineral an amphibole 



*0. Luedecke, Z. d. Geol. Ges., XXVIII, 1876, 249. 

 tA. Sauer, Z. d. Geol. Ges., XL, iS88, 138. 



