347 
M. Beudant on tlw Opals qf'Ht^igary. 
Gpal-jasper occurs also in veins in the solid rocks of the 
trachytic formation; but every where that 1 have met with 
them in this position, I have always observed trachytic or pumi- 
cose conglomerates above tliem ; so that it appeared evident 
enough that they owed their existence to the fine matters which 
the waters had drawn off on passing through the C'onglomerates, 
and which they had subsequently deposited in the cavities 
which occurred on th^r rout. Sometimes they are small veins 
(filons) of cracked opal-jasper, having the appearance of a de- 
siccated siliceous jelly ; sometimes they are veins of oxide of iron, 
impregnated wholly or in part, with siliceous matter; lastly, 
they are sometimes fine white matters, v/hich have here and 
there passed to the state of wax-jasper, or to that of earthy 
opal-jasper. 
It would be useless to point out particular localities for 
opal-jasper ; for it is found every where that pumice-conglome- 
rates exist. I shall content myself with observing here that 
the village of Sajba, near Neusohl, that of Jasztraba, at a 
short distance from Kremnitz ; and, lastly, that of Borfo, on 
the southern declivity of the Schemnitz group, are the most 
celebrated places, and where it appears that beautiful specimens 
are still procured. Those of Sajba are remarkable for the 
beautiful colours which they present, and those of Borfo, for 
the varieties of colour exhibited in the same specimen. 
Opalized Wood . — Opaque opal, more or less coloured, and 
opal-jasper, by impregnating wood buried in the midst of pu- 
micose debris, have given rise to opalized wood (Holzopal^ 
Wern.), which, as we know, presents a great variety of colours 
and degrees of lustre. It is evident that the wood, in this case, 
has merely served as the receptacle of the siliceous m-atter which 
has been successively infiltrated, and in the same manner as it 
has formed in kidneys in the same conglomerates, or been de- 
posited in the fissures of rocks. The organic nature of the 
bodies for which the silica has been' substituted in this case, has 
had no sort of influence on the modification which reduces it to 
the state of opal, since it presents itself Vith the same charac- 
ters, in nests or in veins, in the neighbouring parts where no 
organic debris is found to receive it. A single difference that 
is observed here, and which still proves that the petrifaction is 
