M. Beudanl on the Opals of Hungary, 3SS 
play of colours, are more or less valued as articles of jewellery ; 
others, of a coarser nature, are not the less important in the eyes 
of the naturalist, who finds in their variations, their decomposi- 
tion and their mixtures, the subjects of numerous observations 
of the first importance for science. 
The most celebrated locality for opals is the village named 
Cservenicza by the Sclavonians {Vorbsvagds^ Hung., pronoun- 
ced Toliervenitza and Veu-reuche-vagdche)^ about two miles from 
Kaschau {Kassa^ Hung.), in the trachytic range, which extends 
from Tokaj to Eperies. It appears that these mines have been 
wrought for many ages ; for Eichtel asserts, that, in the archives 
of Kaschau, there exist papers which mention that, in the year 
1400, there were 300 workmen employed in the country of 
Cservenitza, as well for the working of opal as for that of mer- 
cury. At the present day there are not more than 30, but the 
working begins to be conducted with regularity. 
The varieties which, on visiting these mines, I have found the 
most abundant, are, the opaque opal^ of a yellowish or reddish 
white, and the milky opal^ which is more or less translucent. 
The latter becomes sometimes more or less dull, and assumes 
the characters of certain whitish menilite of the neighbourhood 
of Paris. 
The Jire-opaly of a beautiful topaz yellow coloiir, with 
great lustre, and equally beautiful with that which M. De 
Humboldt discovered at Mexico, is still pretty common ; but 
the small masses in which it occurs, are very much cracked, 
and it becomes almost impossible to cut them : it would, how- 
ever, be a very beautiful stone, were it possible to procure pieces 
of tolerable size free of fissures. It appears that the yellow 
colour is owing to iron ; for this stone blackens quickly before 
the blowpipe. It is probable that the metal is here in the 
state of a hydrate, for it is thus that it occurs in the fissures of 
the rock where it is deposited by itself. 
Limpid opal, without colour, occurs pretty frequently in 
the interior of small geodes, the mass of which consists of 
opaque or milky opal ; it forms an undulated crust of greater 
or less thickness, which passes gradually into the preceding 
layer. Sometimes it occurs by itself in minute fissures ; and at 
