372 



ME. A. 31. EINLAYSON ON THE NEPHK1TE [Aug. I909, 



which, he showed, approximate very closely to the percentage 

 composition of the specimens examined. He points out that there 

 is an excess of silicate over that present in the normal silicate of 

 the type R"Si0 3 [4]. 



Dr. Dieseldorff, in his investigations, concluded that a satisfactory 

 chemical formula could not be drawn up, and pointed out that 

 mixtures or contaminations appeared to be present [5]. 



Dr. P. W. Clarke, in his discussion of the results of the extensive 

 and careful analyses of the Heber li. Bishop nephrites, which 

 include specimens from all over the world, concludes that the 

 presence of alumina, soda, and ferric oxide are satisfactorily 

 accounted for, on the assumption that small quantities of the 

 glaucophane {Na 2 Al o (Si0 3 ) 4 {- and riebeckite {Na 3 Fe 3 (Si0 3 )J mole- 

 cules are present, associated with the nephrite molecule. He 

 reduces the analyses, and calculates the percentage composition 

 of the three constituents — nephrite, glaucophane, and riebeckite. 

 The results, which show that this hypothesis accounts very well 

 for all the constituents, give sufficient ground for concluding that 

 Dr. Clarke's interpretation of the composition of nephrite is the 

 ■correct one. 



The results of his calculations of two analyses of Xew Zealand 

 nephrites are here inserted for reference. In making the calcu- 

 lations, he combined the alumina and ferric oxide with enough 

 silica and alkalies to form the glaucophane and riebeckite molecules. 

 The remaining silica was then combined with FeO, MgO, CaO, 

 H„0, to form a silicate, nephrite, of the general formula ESi0 3 

 (where R = Fe, Mg, Ca, H 2 ). The analyses are by Walden, and the 

 reductions by Clarke. 



No. 160 [12, vol. ii, p. 146]. 







Glaucophane 



AlNaSi 2 O e . 



Eiebeckite 

 E 2 " I (Si0 3 ) 3 . 



Nephrite. 



Abstract. 



SiO 



58-14 

 098 

 3-39 

 0-85 

 0-22 

 22-38 

 12-53 

 036 

 1-69 



1-40 

 0-59 



0-36 



4-50 

 0-39 

 3-39 



52-24 



"0 85 



0-22 



22-38 



12-53 



1-30 



Nephrite 89'52 



Glaucophane ... 235 



Eiebeckite 8"28 



excess H 2 ... 0-39 



A1 2 3 



Fe»0 3 



FeO 



MnO 



MgO ... 



100-54 



CaO 



Na^O 



H 2 





Total ...1100-54 



2-35 



8-28 



89-52 





