RUBY. 
397 
enclose the tin-mines of Zinwald, in Ertzghebirghe, 
and in Schlackenwald, in Bohemia ; but in general 
they are of a very small size, and often very opaque. 
Topazes are found in Siberia , in a mountain 
called the Odon-Tchelon. The superior part of 
this mountain, whose sides are covered with ver- 
dure, is terminated by an abrupt cone, like the 
summit of a volcano, having on the south-east side 
a large opening, which resembles a crater. Part of 
this cone is formed of granit, intersected in many 
places by masses of argillaceous or ferrugineous sub- 
stances, in which the topazes are constantly found, 
though always accompanied with emeralds of va- 
rious colours. But they are not confined to this 
part of Siberia alone, as the Uralian mountains 
produce a considerable number, especially about 
twenty-five leagues to the north of Ekateringburg, 
in the environs of Mourzinsk. 
In general the topazes of Siberia are of a very 
pale greenish blue, and become electric when heated. 
Those of Saxony are of a pale yellow, become elec- 
tric when rubbed, and are discoloured by fire. The 
variety found in Brasil are of a lively yellow colour, 
electric when heated, and turn red in the fire. Such 
are the principal characters which distinguish these 
stones from each other ; and these are so trifling, 
that they cannot at best amount to more than mere 
varieties. 
Tavernier mentions a fine topaz belonging to the 
Mogul, weighing 157 carats ; and many others are 
known of a very large size. 
