how delicate a film may have been used. Any one of these tests is sufficient to isolate a false stone.
Some
of the softer genuine stones may be fused together with splinters,
dust, and cuttings of the same stones, and of this product is formed a
larger stone, which, though manufactured, is essentially perfectly
real, possessing exactly the same properties as a naturally formed
stone. Many such stones are obtained as large as an ordinary pin's
head, and are much used commercially for cluster-work in rings,
brooches, for watch-jewels, scarf-pins, and the like, and are capable
of being cut and polished exactly like an original stone. This is a
means of using up to great advantage the lapidary's dust, and though
these products are real stones, perhaps a little more enriched in
colour chemically, they are much cheaper than a natural stone of the
same size and weight.
Some
spurious stones have their colour improved by heat, by being tinged on
the outside, by being tinted throughout with a fixed colour and placed
in a clear setting ; others, again, have a setting of a different line,
so that the reflection of this shall give additional colour and fire to
the stone. For instance, glass diamonds are often set with the whole of
the portion below the girdle hidden, this part of the stone being
silvered like a mirror. Others are set open, being held at the girdle
only, the portion covered by the setting being silvered. Other glass
imitations, such as the opal, have a tolerably good representation of
the " fiery " opal given to them by the admixture, in the glass, of a
little oxide of tin, which makes it somewhat opalescent, and in the
setting is
