341 
M, Beudant m the Opals of Hungary. 
there exists a sterile upper bed, which must be traversed before 
the mass containing the opal can be reached ; probably the re- 
marks of this naturalist apply only to the iridescent opal, which, 
as appeared to me, occurs some feet deeper than the surface of 
the formation. The veins or nests of opaque or milky opal are 
always more numerous and larger than those of the iridescent 
variety. Most commonly, these veins traverse indistinctly all 
the parts of the mass; sometimes the vein bends round blocks 
or masses of trachyte, and is found placed between them and the 
paste by which they are agglutinated ; sometimes it traverses 
the blocks themselves, when they are not of great size, or pene- 
trates into their interior, to a certain depth, when their dimen- 
sions are very considerable. I have observed, that, in the coarser 
conglomerate, the veins were in general pretty large, and that 
there were few nests ; while, on the contrary, in the parts where 
the paste is extremely abundant, I have remarked that the opal 
occurs more particularly in nests, which appear in some measure 
cotemporary with the consolidation of the deposit. Sometimes 
there is even the appearance of the whole mass being consoli- 
dated by an opaline siliceous cement, intimately mixed with the 
6arthy parts, and which is deposited, in a pure state, in the small 
cavities of the rock. 
Cservenitza is not the only place where opal is found. It ap- 
pears that it exists also in the same group of mountains, from 
Bunnita to Erdoeske, at a little distance to the north-west. It 
is certain that it has been extracted formerly above Zamuto, on 
the opposite declivity of the mountains. I have besides, found 
opaque and milky opal in a great number of places where the 
trachy tic conglomerate is abundant ; it occurs round Schemnitz 
and Kremnitz, as well as in the mountains of Matra, and in those 
of Vihorlet. In short, localities are mentioned as occurring in 
many places where the rock is still absolutely of the same kind, 
but nowhere do iridescent opals occur so beautiful and so abun- 
dant as in the neighbourhood of Cservenitza. 
Although, in general, the trachytic conglomerate appears to 
be, in Hungary, the particular matrix of the opals, they occur 
also in other kinds of debris, and even in the rocks in situ, I 
have found the milky variety in the conglomerates of trachy tic 
VOL, VII. NO. 14 . OCT. 18 ^ 2 . 
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