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More about Diamonds. Some Famous Stones
M
ost people
know that diamonds can be white, yellow or blue-white, and that
blue-white stones are considered to be the best, also that
off-coloured or yellow stones are the least esteemed.
What
the average person does not realise is that diamonds may be of any
colour or tint, from coal-black to emerald-green or rose-pink. Their
colouring is due to various metallic oxides. When, therefore, diamonds
are for some time exposed to high temperatures, their colour is apt to
change, though only temporarily. An experiment with diamond, probably
the first of its kind, was carried out by Sir William Crookes, who
embedded a pale-yellow diamond in radium bromide for eleven weeks. At
the end of that time, the pale yellow had changed into a bluish green.
I
myself saw and handled an eight-carat stone which, by the same means,
had been turned from brown into a poor tourmaline-green. In my opinion
the stone had been
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