518 J. F. KEMP AND J. G. ROSS 



is probably not far from the truth. In order to separate the 

 biotite, it is assumed that its composition is similar to the 

 analysis given in Rosenbusch's Elemente der Gesteine, p. 234, 

 for one from a monchi quite (which analysis is quoted in the 

 Classification of Igneous Rocks, Table XIV.) On this basis the 

 results are as follows : 



Biotite 20.89% 



Olivine 6.30 



Serpentine 29.25 



Perofskite 2.31 



Ilmenite 6.38 



Magnetite 2 .09 



Apatite 1.68 



Analcite 1.58 



Calcite 16.60 



Magnesite 8.23 



Quartz 4.98 



Total 100.29 



Water 0.83 



Grand Total 1 



01.12 



It is evident that some very rich calcium-bearing mineral 

 must have contributed the calcite. Anorthite, diopside, and 

 melilite will at once suggest themselves. Anorthite is out of 

 the question, because the alumina fails. If diopside or some 

 other monoclinic pyroxene had been once in the rock, we ought 

 to see the outlines of its crystals still remaining. Melilite is 

 the most probable, but if it were once present, its destruction 

 has been very thorough. A richly calciferous glass or basis 

 seems to be the only possible further assumption. 



In conclusion acknowledgments are due to Drs. C. P. Berkey 

 and A. A. Julien for assistance regarding some puzzling features 

 of the microscopic mineralogy; to Miss Adams for the analysis, 

 and to Donald Ross for aid in the field. 



