132 THE INCLUSIONS OF THE VOLCANIC ROCKS 



made by mounting the powder in a solution of Canada balsam and xylol. With a little 

 practice very rapid examination may be made by this method, and in particular it is 

 more easy to distinguish olivine and pyroxene thus than in a thin section. Any mineral 

 present in small amount may, however, easily escape detection. 



These nodules consist of associations of two or more of the following minerals: 

 olivine, a pale green augite (chrome-diopside), rhombic pyroxenes, brown hornblende, 

 biotite, a basic plagioclase, and a spinel. The associations are shown in the following 

 table : 



The olivine is pale green in colour and very free from inclusions. The impregnation 

 with magnetite, described and figured by Prior* in some of his specimens, does not appear 

 to be represented in the present collection. A few of the nodules, however, are of a 

 reddish colour (" rubifie ") owing to the separation of limonite from the olivine. The 



* Loc. cit., p. 10S. 



