AGATE. 
4UJ 
Chalcedony. 
7 his variety of agate, which derives its name 
from the antient city of Chalcedonia, situated on 
the eastern side of the Bosphorus, where it was first 
noticed, and where it is still occasionally found, is 
of a white colour, like milk diluted with water, and 
is marked with veins, circles, and round spots. 
Chalcedony is found of the same form and in the 
same situations as the agate : like that stone it fre- 
quently occurs in hollow balls lined with crystals of 
white or violet quartz : sometimes it is found in 
solid masses of an oval shape. Patrin has recorded 
some among those which are met with in the form 
of hollow balls, that exhibit a phenomenon exceed- 
ingly curious and very difficult to be explained. 
On the right bank of the river Chilka, among some 
volcanic hills, balls of chalcedony are found con- 
taining crystals of quartz surmounted by others of 
calcareous spar. In this there is nothing more than 
common ; but what distinguishes these balls from 
others is, that all the space which is usually left in 
the middle of other balls, in these is filled with 
maltha , or black mineral pitch of a solid consistence. 
It will be extremely difficult to account for the in- 
troduction of this inflammable matter, as the stones 
appear perfectly sound, and without the smallest 
crack or fissure. To add still more to the singu- 
larity of the circumstance, not a vestige of mineral 
pitch is to be found in the neighbourhood of the 
stones, which are completely enveloped in a crust 
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