_ Account of some new Vesuvian Minerals. 267 
Foiiacsous Copper. 
The chimnies constantly burning on the east of the crater 
of Vesuvius have furnished a sublimation, composed of 
acicular and rectangular laminz, some of such extreme 
subtility and fragility, that it is scarcely possible to procure 
them eutire, since they are broken by the slightest jar, or even 
agitation of the air. Viewed at an oblique angle, they pre- 
sent the brown colour of shining steel, but seen perpendicu- 
larly, they exhibit a velvet brown. ed in the interior © 
of these chimnies, the laminze and their matrices are accompa- 
nied by muriate of soda ; and are often imbedded in this salt, 
which takes the green colour of the metal. The matrix is 
usually an aggregate. 
The thickness of these leaves is about 4 lines, resembling 
similar plates of gold or silver, but are much more frangible. 
They dissolve quickly in nitric acid, without a residuum, 
imparting a beautiful green colour, which is changed to in- 
digo blue by the addition of ammonia; a certain indication 
of copper. An exact analysis of the sublimation has not 
yet been made. : 
It appears probable that this metallic sublimation 1s not 
roduced by heat solely, but is favoured by an acid, which 
renders the metal fragile. It is so intimately combined with 
muriate of soda, as not to be freed from it by washings with 
distilled water. Still it may be doubted if either the muriatic 
er the arsenical acid is concerned in its formation. The 
authors will institute experiments to ascertain that point. 
