SECTION III. 1883. Sze} TRANS. Roy. Soc. CANADA. 
On Cryptomorphism in its Relations to Classification and Mineral Types. 
By E. J. CHapMan, Ph. D. Professor in University College, Toronto. 
(Read May 24, 1883.) 
The term “cryptomorphism ” is proposed—in default of any special term hitherto 
employed in the same sense— to denote the condition, necessarily concealed, of an element 
or elementary compound in combination with other elementary bodies. The assumption 
that bodies in combination always retain the conditions which they present in their known 
free state is manifestly untenable: and yet it is tacitly acted upon in all mineralogical 
classifications based on chemical or physico-chemical principles—whether the electro- 
negative or the electro-positive element be made the basis of the classification. In this 
manner, substances are often grouped together without regard to real character and affinities. 
The metals zinc and magnesium, for instance, as obtained in the free state have evidently 
very close relations; and in most of the compounds into which these metals enter there is 
a corresponding relationship. But this does not hold good throughout. The simple oxides 
ZnO and MgO, as artificially obtained, may be co-related ; and in these, as well as in 
most zinc and magnesium salts it may perhaps be fairly assumed that the metals are in a 
similar or essentially similar physical condition: but in their natural oxides, zincite and 
periclase, the two metals are clearly in very different cryptomorphic conditions. Beyond 
the fact (or conventionally-assumed fact) of being equally monoxides, where are the homo- 
logies of these minerals? They have actually none; and practically no resemblances, 
even, in common. In general form, hardness, geological conditions of occurrence—they 
are totally distinct. The zinc compound is far more closely related to the natural sulphide 
of that metal, in which the generally non-metallic lustre, and strong resistance to fusion 
and volatilization, are essentially opposed to the ordinary characteristics of metallic sul- 
phides, as well as to those of its components, sulphur and zinc, in their known free con- 
dition. Periclase, on the other hand, from its form, remarkable hardness, and geological 
relations, is far more nearly related to the alumino-magnesian spinels. 
It would seem clear, therefore, that there must be several kinds of zine and several 
kinds of magnesium: although only one kind, of each, is known as yet in the free state. 
And as with zinc and magnesium, so with other elementary bodies, as rendered certain in 
several cases by a difference in quantivalence and other properties, and in some cases by 
visible allotropism. 
In combinations, the physical or physico-chemical condition of one component may 
impart its character, by contact, to the entire compound; or, and this is evidently the 
more general case, by mutual contact of the components, a concealed-allotropie or crypto- 
morphic change may be induced in all. In the latter case, the essential character of the 
compound may depend in some instances on the condition of one component, and, in others, 
Sec. IIL, 1883. 8. 
