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A Necessary Introduction xv
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of
gem stone, so that colour in itself is absolutely no guide in its
identification. A blue stone is not necessarily a sapphire, and a
sapphire is not necessarily blue.
In
the last resort, where there is any doubt about the nature of a gem,
even the trained expert must go to the scientist for tests which will
establish the mineral's specific gravity, refractive index, dispersion
and polarization. The eye alone and unaided cannot always be sure.
There
are other interesting facts worth remembering about gems, apart
altogether from their "human interest" value. One is inclined to think
of them as almost imÂperishable, and yet even diamonds may be
destroyed, for instance, by fire when air is excluded—completely
destroyed; and nearly every gem stone, when long immersed in strong
acids, may be turned into a soft jellified mass. On the other hand, if
you happen to let a gem fall into the fire you can save it if you rake
it out quickly enough, and even if it has become dulled it can be
repolished, whereas once a pearl has met with such an accident it is
done for.
I
add this because it may save me from being dragged from my bed to the
telephone on a cold winter's night, as once happened. An unknown reader
rang me up to tell me that his wife had just lost her pearl ring in the
open grate and what should he do about it?
I
said: "Rake out the ash at once. It may have dropped through into the
cinders, in which case maybe only the outer skin will have been burnt,
and that of course can be scaled." Upon which I went back to bed again.
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