- NATIVE COPPER IODIDE AND OTHER MINERALS. ook 
difference in crystalline structure, and mineral associations between 
the three minerals ; for instance the so-called hedyphane is (1st): 
usually in short hexagonal prisms. (2nd) The crystals are often 
coated by films of what appears to be different material, in which 
case they are usually accompanied by iodide of silver, being in all 
cases the latest deposit. On the other hand mimetite or pyro- 
morphite when occurring as hexagonal prisms, have a widely 
different appearance, the latter being usually flat topped or but. 
slightly bevelled, while the former is generally truncated, much 
bent or bulged out as it were at the top; while the incrusting 
film and accompanying iodide of silver characteristic of hedyphane 
(?) have not yet been noticed. 
(No. 4) Another peculiarity in composition is found in a mineral 
that I have classed as aurichalcite. It consists essentially of 
zinc-copper carbonate ; some samples containing water others not. 
The latter can scarcely be classed as smithsonite since it contains. 
from traces to 37% of copper. This mineral occurs usually as 
implanted semi-transparent crystals, from a sky-blue to dark 
_bluish-green colour. It is the opinion of many that the copper 
present is only a mechanica] impurity. I look upon it however, 
as being in chemical combination. Amongst the numerous speci- 
mens of this mineral in the collection, it would be almost impos- 
sible to get two of similar appearance and composition. ‘This is 
not only true of the zinc minerals, it applies also to the various 
lead, copper, and silver ores belonging to this collection, I recog- 
nized this fact early in the progress of my work here, and discovered 
that in order to render the classification of this (7.e. the Aldridge) 
collection useful and instructive, it would be necessary to base it. 
on the more essential constituents of the minerals, neglecting in. 
many cases their minor differences, otherwise the classification. 
would have been encumbered by unimportant information, and 
the list of varieties carried to an extreme limit. 
[This mineral is zinc carbonate containing small quantities of 
copper, the amount of copper is not sufficient to regard the mineral 
as aurichalcite. 
