112 
ON ARTIFICIAL AVENTURINE. 
examine the redaction which oxides at the minimum of oxi- 
dation are capahle of effecting on protoxide of copper, and 
our attention was principally directed to the action in this 
way of iron scales. 
We have found that, under the influence of heat, iron 
scales quickly reduce the protoxide of copper to the metallic 
state, passing itself to the state of peroxide of iron. This 
reaction appeared well suited to fulfil the end we proposed; 
it produces pure copper, and has the advantage of forming 
a metallic oxide, soluble in the glass, and giving it only a 
slight yellow tint. The formation of a silicate of peroxide 
of iron is a fortunate circumstance, for, by increasing the 
density of the glass, this silicate would naturally oppose the 
deposition of the metallic crystals. We, therefore, with con- 
fidence tried to produce Venitian aventurine by heating a 
mixture of glass, protoxide of copper, and iron scales. 
The experiment confirmed our anticipations. 
On heating for twelve hours a mixture of 300 parts of 
powdered glass, 40 parts of protoxide of copper, and SO 
parts of iron scales, and then allowing it to cool very slowly, 
we obtained a vitreous mass, containing, in abundance, 
crystals of metallic copper. 
The most difficult point in the manufacture of aventurine, 
namely, the production of a glass containing brilliant crys- 
tals of copper, uniformly diffused through the mass, has, 
therefore, been completely resolved. 
The specimens of aventurine which we now present to 
the Academy, have a certain degree of opacity which de- 
stroys the brilliancy of the metallic crystals, and these crys- 
tals also are not so large as they should be ; but the expe- 
riments we are now making lead us to hope that we shall 
soon have specimens completely satisfactory. 
To convince ourselves of the identity of our aventurine 
with that made at Venice, we have examined them with 
an excellent microscope, and we find that in both the cop- 
per is crystallized in regular octahedrons. — Pharm. Journ. 
from Journal de Pharmacie. 
