162 E. J. CHAPMAN ON MIMETISM IN INOEGANIC NATUEE. 



so-called " phosphate " of this region occurs, it is well known, in lenticular or irregular 

 masses, often of large size, associated with maguesian mica (i.e., phlogopite), pyroxene and 

 calcite, the mica and the pyroxene appearing in some places to surround or enclose the 

 apatite, after the manner of an enclosed or " sheathed " ore-stock. In different deposits, 

 and in different parts of the same deposit, various other minerals are often subordinately 

 present, and some of these resemble each other in a very striking and peculiar manner. 



All who are familiar with our apatite deposits know, for instance, how frequently 

 certain associated varieties of pyroxene are mistaken for phosphate, even by explorers of 

 fair pretensions to be considered experts. Some examples are indeed strikingly alike : 

 and yet apatite and pyroxene are never referred to in mineralogical text-books as likely to 

 be mistaken for one another. The resemblance is in fact a local resemblance only. Scapo- 

 lite and apatite, again, have in general but few points in common ; but in many of the 

 scapolites of these phosphate deposits the likeness is very strong — even to the rounded (as 

 though semi-fused or semi-dissolved) edges, the peculiar sub-oily lustre, and stirface 

 characters generally. Much of the pyroxene, likewise, of these phosphate deposits closely 

 resembles the associated scapolite. Viewed generally, each of these species, as we know, 

 has several A^arieties, some of which are very distinct in aspect ; but, in the association of 

 these two minerals in our phosphate deposits, closely resembling varieties chiefly come 

 together. But of all these mutual resemblances, none, perhaps, are so striking and so 

 unexpected as those presented by the examples of quartz and zircon which occur in these 

 phosphate deposits. As a rule, these two minerals could scarcely be confounded even by 

 the least experienced eye ; but here they present the same dark-red colour, the same resino- 

 vitreous lustre, the same peculiar wrinkled or pitted surfaces (left apparently by the decay 

 of minute crystals of apatite), and thus look in almost every respect alike. But, of course, 

 in all of these resemblances, the fundamental character of the mineral, viz., its composition 

 and its essential ci-ystallization, necessarily remains u^nchanged : just as the insect is still 

 the insect, while closely resembling the leaf or other deceptive form. 



