114 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



For Na oj = 1.6691 



e= 1.6568 



For Uw= 1.6758 ± .0002 

 c = 1.6647 ± .0002 



The figures for Li are inaccurate in the fourth decimal to two or more 

 places, owing to the indistinctness of the boundary line. 



Unlike the original material, the mineral gives a strong sodium flame, 

 and the following analysis of the new material (I) was therefore 

 made : * 



I. Analysis of new material. 



II. Analysis of new material reiluced to 100 omitting Ig. 



III. and IV. Molecular proportions. 

 V. Analysis of original material. 



It is seen that the alkalies replace in part the Ca and Mg, but that 

 there is still a molecular excess of the alkalies. The thin sections show, 

 in addition to numerous fluid inclusions, the presence of frequent small 

 grains of an undetermined mineral to which the content in alkalies may 

 be partly due. 



* Both analysis and optical determinations were made by me in the Miner- 

 alogical Institute at Munich. 



