376 J. D. Dana on Serpentine Pseudomorphs 
difficulty of separating it entirely from the serpentine, only a 
qualitative analysis has been made of it by. Professor Allen; 
and this indicated the. presence of carbonic acid, magnesia, and 
lime, and left no reason to doubt its identity with the ordinary 
dolomite of the mine and of other parts of the specimens. 
2. Structure.—The structure is the same for the pseudomorphs 
consisting of both serpentine and dolomite, as for those of ser- . 
pentine alone. A description of the former, which is of greater 
interest, will, therefore, suffice for both. 
ese compound pseudomorphs usually constitute easily- 
cleavable masses, two or three inches th 1 r 
erals are united in one crystallized mass, not by intimate mix- ' 
ture, but by side-by-side juxtapositions of independent rectan- 
gular blocks or layers of each, all fitted together like parts of a 
simple crystal. 
The cleavage is cubic and exceedingly perfect, without the 
in fig. 3 is given separately in fig. 4. Some of the rectangular 
3. Origin of the Pseudomorphs.—This combination of two so 
distinct Minerals, one a hydrous silicate and the other a car- 
cae stalline mass i 
cleavage, is that, for one or both, the form is pseudo- 
vanelde ges! -hat both are so, is made manifest by the struc- 
miner 
f Ppesiverib aap me shows itself to be pseudo- 
_ Morphous by the fact that the cleavage is not true cleavage, but 
