the Identity of Gems. 217
The
pink topaz is frequently confounded with the balas ruby, the tourmaline
with the emerald, the jacinth with the cinnamon stone, and the jargoon
and white sapphire with the diamond; not only by amateurs, but even by
persons supposed to be acquainted with precious stones. A very little
attention to the facts noted under each head, both in the Table A and
in the description of each stone, will prevent the errors into which
many persons fall, and the possibility of the frauds to which they are
occasionally liable.
In
the first place, it may be taken as a general rule that stones, either
rough or cut, which are affected by the file, are not precious stones;
and to persons who are accustomed to its use, the difference of the
resistance, and of the grating sound occasioned, affords a fair
criterion of hardness. In the use of this tool, however, care must be
taken not to file the delicate edges; as even the diamond, the hardest
of bodies, might chip, if subjected to the tool on the girdle, which,
as has before been said, is as thin as the edge of a knife.
For
example, supposing it were wished to ascertain what gem a white stone
was :—if it were scratched by a sapphire, it would at once be seen, on
reference to the Table A, that it could not be a diamond; if its
specific gravity were less than 3.9, it could not be a ruby or
sapphire; if it did not acquire electricity by heat, it could be
neither a topaz nor a jargoon; and if it scratched glass, it would be
seen that it must be either a beryl, or quartz, or rock-crystal. For
the pur-
