34S 
M. Beudant mi the OpaU ()/' Hungary. 
other by a great' number of gradations. They are all extreme- 
ly brittle, and break into a multitude of fragments on the least 
blow. They are also soft, and may be scratched with great ease 
by the knife, unless when, being purer and semitransparent, they 
pass into opal, Hint, or common jasper. ' . 
The purest opal-jasper, which is only an impure variety ot 
the Semiopal of Werner, presents a yellowish or greenish colour ; 
its fracture is sometimes conchoidal, more or less perfect, but 
most commonly splintery, with the splinters pretty distinctly de- 
fined, and the lustre is that of wax. Heated slowly to redness, 
this kind of opal assumes a brownish colour, which seems to in- 
dicate that the colouring matter is oxide of iron. 
On the one hand, this variety assumes a little transparency, 
and then passes into wax-opal, of which it certainly is only a par- 
ticular state. On the other side, it becomes grad ually softer, 
loses its colour by little and little, and then passes into an impure 
substance, with an earthy fracture, and a yellowish or green- 
ish white colour, which may be designated by the name ol 
Earthy Opal-Jasper, This kind adheres strongly to the tongue ; 
it readily imbibes w^ater, and then assumes a slight semiti^anspa- 
rence, and a yellowish or greenish colour, precisely like the wax- 
opal ; it does not blacken in the fire ; but when it has been 
strongly heated, it becomes transparent, and perfectly limpid oil 
the edges, precisely in the same manner as we have seen with 
regard to the altered opal. These characters, added to the cir- 
cumstance that this variety always forms the outer part of the 
kidneys, while, toward the centre, we find the pure waxy opal- 
jasper, might make us suppose that it is a state produced by de- 
composition ; but this is probably not the case, as we shall sho'^^ 
afterwards. - 
The iron is also found to introduce itself gradually in greater 
or less quantity, and varieties soon occur which are extremely 
loaded with it, and which might be designated by the name of 
Ferruginous Opal- Jasper, The colour is deep, of a blackish 
brown, or chesnut brown, passing sometimes into ochre yellow : 
these various tints are sometimes united, and form veined or 
spotted delineations. The fracture is commonly conchoidal, and 
the lustre is pretty analogous to that of resin. It is this circum- 
stance which has occasionally caused this substance to be called 
z S 
