Vol. 4 1 Murgoci. — Classification of the Amphiboles. 



369 



book. One can see (in Table I) that rhodusite is the Fe-end 



member of the glaucophane series. Its constitution is that of a 



glaucophane where Al is replaced by Fe : 



f Na.SiO.. 

 I Fe"Si0 3 



-j 2MgSi0 3 (very little Ca.) 



| FeSi.,O 

 L H 2 SiO a 



It is a pity that, except pleochroism like that of glaucophane 

 and an uncertain angle of extinction (4°?), we possess no other 

 properties of this interesting' end member of the glaucophane 

 series. 



We find in the literature (Hintze p. 1267, Dana p. 401) an- 

 other mineral, which in its occurrence, form, and chemical com- 

 position is quite similar to rhodusite, viz.: Heddle's abriachanite, 

 a blue fibrous substance found in the clefts of the Old Eed con- 

 glomerates, underlying schists, granite, etc., from Abriaehan 

 (Scotland), etc. Dana and others have considered abriachanite 

 as related to crocidolite, but that is not the case. Abriachanite, 

 like -rhodusite, is an iron amphibole very poor in lime, rich in 

 magnesia (like glaucophane), while crocidolite is an iron am- 

 phibole very poor in lime and also in magnesia (like riebeekite, 

 as Lacroix has stated). 



One analysis of abriachanite (XV) poor in soda (Hintze p. 

 1268) seems to represent the Fe'" — glaucophane corresponding 

 to the gastaldite formula. But, as we have no other details about 

 the properties of abriachanite regarding its similarity with rho- 

 dusite, and as rhodusite is better known, I propose to identify 

 abriachanite with rhodusite, and to retain the name rhodusite for 

 the end member (rich in Fe) of the glaucophane series. 



Crocidolite (f). — I had the opportunity of studying some 

 bine amphiboles like crocidolite, in some syenites which show ex- 

 actly the same mineralogical composition and phenomena as have 

 been described by Chestner, W. Cross, A. C. Lane, and others, in 

 many such rocks. The occurrence, the form, and the rather ob- 

 scure properties make the determination of these minerals very 

 difficult and their identification with other minerals (crocidolite, 

 rhodusite, etc.) almost impossible. As the properties of crocido- 

 lite are insufficiently known (pleochroism and absorption like 



