270 Warren — Ilmenite Boohs near St. T/rbain, Quebec / 



mass. Again, the feldspar may be surrounded by sapphirine 

 of nearly or quite equal area. About a single feldspar grain 

 the sapphirine usually has, throughout the greater portion of 

 its extent, a uniform orientation. The mineral also includes 

 ilmenite and rutile grains, and in one instance, at least, has 

 been noted in contact with spinel. Where the feldspar is more 

 abundant the sapphirine is also more strongly developed and 

 its grains have in some instances fairly continuous distribution 



Fig. 1. 



Fig. 1. Microphotograph of thin-section, showing plagioclase (white) al- 

 most entirely surrounded by sapphirine (gray) either as a narrow band or as 

 larger grains between it and the ilmenite (black) or rutile (dark, mottled). 

 The plagioclase shows many minute microlites of spinel. Magnif. about 

 90 ; ordinary light. 



through the section, and often lie, with and without included 

 ilmenite and rutile, between the feldspar crystals, or even 

 included in them. In such sections as much as 20 per cent 

 has been observed with about an equal amount of feldspar and 

 rutile, a little spinel, and the remainder ilmenite. Here, the 

 grains frequently attain a diameter of 



larger 



3-0 mm , the aver 



