I92I. No. 8. ox THE ECLOGUES OF NORWAY. Ill 



It niav be seen, under the microscope, that the ore grains are evenly 

 distributed and enclosed in all the minerals including garnet. 



The hornblende is of the common green variety, ha\ing ß ~ 1.665 

 ± 0.003. The plagioclase shows, in sections _L PM, extinction angles of 

 25° — 27 '\ corresponding to Abj., — Ab^^. 



Minor constituents are apatite and zircon. 



Sometimes the hornblende and sometimes the plagioclase shows greater 

 tendency towards an idiomorphic development, and it is not possible to 

 state with certainty, whether the structure may be regarded as crystal- 

 loblastic or as a consolidation structure. 



The réfringence of the hornblende (ß = 1.665) points, according to 

 Ford's diagrams, to a hornblende containing about 13 percent FeO and 

 13 percent MgO, or an amphibole with a considerable molecular pre- 

 ponderance of magnesia. This is interesting, the garnet being so very 

 much richer in the iron compound. 



Hornblende-gabbro from Haugen, Meinkjær, Bamle. 



The specimen studied was collected b\' \V. Werenskiold and repre- 

 sents the amphibolitic border zone of a norite mass. It is a medium-grained 

 feldspar-hornblende-rock containing red crystals of garnet of the size of peas 

 at rather regular intervals of two or three cm. 



The garnet was separated and an analysis of it was made by the 

 writer with the following result : 



100.28 



Sp.g. = 3-984- 



"d = 1.7864. 



RO : R0O3 : SiO., = 3.11 : I : 3.14. 



Composition : Fe6iMn.,Mg.25Cai.,. 



The garnet is poor in inclusions. Only grains of ilmenite were 

 observed in it and these are as numerous, when enclosed in the garnet, 

 and of the same shape as when enclosed in the other minerals. 



