I
felt as if we were entering a hospital. Here were an X-ray unit,
several high-powered microscopes, and a spectroscope. Dr. Custers
explained how light is shot through a diamond crystal and analyzed on a
spectrographic plate. From the width and intensity of the resulting
bands of color the observer can deduce what elements are present in the
crystal—elements, that is, in addition to the carbon that makes up pure
diamond. One of Dr. Custers' special studies is that of color in
diamond and its causes, and he said that nearly every diamond in nature
does contain small amounts of foreign elements, some of which —cobalt,
iron, titanium, and chromium—almost certainly affect diamond color. He
added that there is still a lot to be learned on the subject and that
he has his own ideas about it, but for the moment he didn't elaborate.
Quite
apart from these naturally colored stones, he said, are those which
have been treated in the laboratory and their color charlged
deliberately by irradiation in an atomic pile, which turns them green.
The depth and strength of the greenness depends on the amount of
irradiation, a strong dose producing such a deep bottle green that the
stones look black. When a green diamond of this kind is heated, it
changes color yet again, this time to amber or yellow. The
greater the heat, the more the diamond reverts to its original clarity,
that quality usually known as "pure white" or "blue-white," but an
irradiated stone never loses all its yellow tinge. "In other words,"
said Dr. Custers, "some of the radiation damage is permanent. We don't
know why." He added that diamonds found near uranium deposits are
often green.
Speaking in what must have sounded to himself like baby talk, and looking alternately at my guide and me, he explained
