ON ARTIFICIAL AVENTURINE. 
Ill 
to obtain results, which although not brought to the highest 
degree of perfection, are, notwithstanding, of a nature to 
induce a belief that in future aventurine will be manufac- 
tured in France. 
As we wish to supply to our manufacturers, as soon as 
possible, the deficiency which has existed with reference to 
ihis product, we hasten to make known our process for the 
manufacture of aventurine, hoping that they may bring it 
to that perfection which practice alone can give it. 
The. chemical analyses, made principally by MM. Wohler 
and Barreswil, have proved that Venetian aventurine is 
composed of a soft glass holding in suspension metallic and 
crystallized copper. It appeared, then, that aventurine 
should be obtained by crystallizing copper in melted glass, 
and having the mixture in such a state that the metallic 
crystals shall remain disseminated through the vitreous 
mass. 
But knowing the tendency of copper to oxidation, and 
its fusibility, and appreciating all the circumstances opposed 
to its crystallization, and the equal diffusion of these crystals 
through the fused glass, it will be easy to understand the 
difficulties we had to surmount. 
The choice of the composition which, by the action of 
heat, should afford metallic copper, was not less difficult. 
We found it necessary to reject those bodies which, in pro- 
ducing copper, would require a temperature^either too high 
or too low ; in the first case the metal would become agglo- 
merated before the fusion of the glass ; in the second, it 
would fuse, separate from the glass, and collect at the bot- 
tom of the crucible. Neither could we admit of those reac- 
tions, which, in producing metallic copper, would give rise 
to an abundant disengagement of gas, or the deposition of 
a coloured or insoluble deposit in the glass. A composition 
had to be found which, at the temperature of the fusion of 
glass, would produce metallic copper. 
After trying without success the action of different metals 
on glass coloured by oxide of copper, we have been led to 
