258 J. D. TRUEMAN 
value of monazite as a criterion is, however, lessened by the 
fact that several cases have been observed in which it is clearly 
secondary in a metamorphic rock. In addition to secondary 
enlargements of rounded grains, Derby has noted clear crystals 
containing inclusions of hematite and rutile and, accordingly, 
almost certainly of secondary origin. Perhaps the chief applica- 
tion of monazite in the indentification of metamorphic rocks will be 
found in its use as an aid in the recognition of the unaltered phase 
of a metamorphic rock when the original type still exists. 
Xenotime, YPO,, is somewhat similar in its character and 
occurrence to xenotime. It has, however, even a more limited 
distribution than the latter. 
[To be continued | 
