I92I. No. 8. 0\ THE ECl.OC.ITES OF NORWAY. 4I 



This rock attracted my interest because its pyroxene showed a rather 

 striking optical characteristic, in having an exceptionally low birefringence: 

 in a section of 0.02 mm thickness the highest interference colour is pale 

 yellow of the first order, as in the orthopyroxenes. Knowing from Laura 

 Hezner's description ' an eclogite-rock from Schaffis, Switzerland, whose 

 pyroxene shares this character and contains much alumina and lime, I decided 

 to separate the pyroxene from the Saltkjael eclogite for analysis. 



The minerals, however, almost defied separation. Three separations 

 were necessar}', and the sample obtained, floating at sp. g. 3.320 and 

 sinking at sp. g. = 3.356 and consisting of approximately pure pyroxene, 

 was but 0.4 g in weight. On this amount an anal^-sis was carried out 

 by Mr. L. Thomassen : 



99.14 



Sp-g. 3-34 

 ß = 1-685 i 0-003- 

 Y — « -^ 0.018 ± 0.00 1. 

 2Vy = 60 appr. 

 No noticeable dispersion of the optic axes. 

 Colourless in thin section. 



The state of oxidation of the iron was not determined. The 

 optical properties, however, make it probable that only ferrous oxide 

 is present. 



This analvsis ma}' be calculated in the following way: 



' L.iura Hezner, Ueber einige in schweizerischen Pfahlbauten gefundene Steinwerkzeuge, 

 N. J. Min. etc. B.-B. XX, 1905 p. 141. 



