232 C. iT. Fenner — Crystallization of a Basaltic Magma 



with chloritic areas retaining a suggestion of a crystal unit, 

 and again scattered through the glass. 



Fig. 14. 



Fig. 14. Inclusions in glass, resulting from the breaking-up of olivine 

 crystals. (Slide No. 17.) Diameter of field l'5 mm . 



These effects are shown in slide No. 17, sketched in fig. 14. 

 The greenish glass is filled in places with brownish inclusions, 

 arranged in crescentric or cusp-like figures. The inclusions 

 appear to be in part surviving fragments of olivine, and in 

 part magnetite dust set free in the reaction. The figures 



Fig. 15. 



Fig. 15. Effects of resorption of olivine accentuated by secondary altera- 

 tion. (Slide No. 54.) Diameter of field l'5 mm . 



assumed would appear to be due to the manner in which the 

 resorbed material was diffusing in the surrounding magma 

 when increasing viscosity terminated the process. Diopside 

 and plagiociase are present in minor amount. 



A slight degree of subsequent zeolitic alteration of glasses 

 containing partially resorbed olivines serves to accentuate the 

 features described. This is seen in slide No. 54 (fig. 15) and 

 in many other cases. Even in advanced stages of secondary 

 alteration traces of these features persist. 



