130 CLASSIFICATION. 



PART n. 



CLASSIFICATION. 



. 104. IDENTITY. 



Minerals, (or Individuals,) not differing from each other 

 in any of their natural properties, are identical. 



This may be considered as an axiom, not only in mineralogy, but 

 in Natural History generally, and lies at the foundation of the whole 

 theory of the systems in these sciences. 



It requires, however, some limitation, or explanation. 



By natural properties, must not be understood every property 

 with which these productions are endowed, since there are several, 

 which, as they are of no utility for the purposes of mineralogy, are 

 not included in the above expression. Such are, besides the size of 

 crystals, also the disproportionate enlargement of some of their faces, 

 their junction with other individuals, their being implanted, imbed- 

 ded, SLC. These are called the accidental properties of minerals ; 

 and individuals which differ only in these respects, are taken for 

 identical ones, equally with those which do not, or which are simi- 

 lar in respect to such circumstances. 



Farther; individuals are allowed a certain deviation from per- 

 fect similarity in their natural properties, and are still said to be 

 identical. 



The forms, for example, among several individuals, are not re- 

 quired to be the same ; provided they are members of one and the 

 same series of crystallization, (their remaining properties not being 

 dissimilar,) they are identical. Thus, in the species Fluor, indi- 

 viduals possessed of the form of the Cube, the regular Octahedron, 

 and of the Podecahedron, are of frequent occurrence, but whose 

 other properties, (as color, hardness, specific gravity, &c.) are simi- 

 lar. Such individuals are identical, because the Cube, the Octa- 

 hedron, and the Dodecahedron, are members of the same series of 

 crystallization. If we suppose an individual to occur, agreeing with 

 those just mentioned, excepting in form, which we will imagine to 

 be that of the Rhomboid; such an Individual cannot be said to be 

 identical with the others, since the difference between it and them 



