M. Beudant on the OpixU Hungary. 34,5 
collected, and which have broken them into small fragments even 
in my drawers, announce incontestibly a substance which con- 
tains much waterj and which has undergone a greater or less 
contraction in proportion as this fluid has evaporated. These 
circumstances are still in favour of the hypothesis of which I 
have spoken in the article on Opals ; and it seems impossible not 
to come to the conclusion in a similar case, that a part of the 
opals and opal-jaspers, are not the result of a gelatinous preci- 
pitate of silica, consolidated sometimes by desiccation, sometimes, 
perhapS;^ by an infiltration of siliceous matter in a state of solu- 
tion. This infiltration might easily explain the passages of opal 
into calcedony ; and, at the same time, those characters in some 
measure intermediate between the two substances, which are so 
frequently observed. In fact, it may easily be conceived, that 
a calcedonic liquid may have sometimes penetrated the gelati- 
nous precipitate in greater or less quantity. 
The opal-jasper is susceptible of alteration like opal, properly 
so called, and there result solid substances, capable of imbibing 
water, and of their regaining a part of their original lustre, or 
earthy matters which mix with water. But there exists a great 
difierence between the alteration which takes place from expos- 
ure to the air, and that which takes place in the interior of the 
earth. Opal-jasper exposed to the air, even the most ferrugi- 
nous varieties, becomes entirely white, and similar to hydro- 
phane or cacholong : it appears that the oxide of iron is succes- 
sively removed in this operation. The stone, nevertheless, pre- 
serves a great degree of consistence ; it adheres strongly to the 
tongue ; imbibes water, and becomes translucid, without regain- 
ing any colour ; it remains equally white after having been ex- 
q)osed to a red heat ; and, in a clear fire, it becomes perfectly 
transparent on the edges, as is the case with altered opal. When, 
on the other hand, decomposition has taken place in the interior 
of the earth, the mass loses its consistence, and becomes soft to 
the touch ; the oxide of iron constantly remains, and there re- 
sults a kind of argillaceous matter, of an ochre-yellow colour, 
which imbibes water, and assumes the original colour of the 
stone, as well as more or less translucidity. It is to this last 
kind of decomposition that the state of opal-iasper which we have 
designated by the name of earthy^ might be attributed, were 
