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FIRE IN THE EARTH
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la
Bijouterie in Paris proposed that the carat weight should be made
exactly 0.205 gram. But not until 1907 was the so-called metric carat
of 200 milligrams generally accepted. Even after that Great Britain
gave little consideration to the new system. But in July, 1912, the
Education Committee of the National Association of Goldsmiths adopted
the metric carat as the legal weight for precious stones. Even so, it
was not until two years later that it was accepted, and it was not
adopted in South Africa, the home of almost 95 per cent of the world's
diamond production, until 1923. The United States adopted it in 1914.
When
you think of the shape of diamonds—what the scientists put under the
heading of crystallization and structure^—you have to visualize a few
things first to understand how they achieved crystal shapes, generally
known as octahedron, tetrakishexahedron, and hexakisoctahedron, twinned
octahedrons. The octahedron, or real diamond-shaped stone, is the most
familiar to us all, whether we wear them or play bridge or poker or
pinochle. How did it get that way? The scientific explanation,
complicated as it is, is more dependable than a popular one, but a
popular one might enable us better to get the hang of what the
scientist is talking about. (The oldest theory is: the diamond travels
through the earth, up from the very center, propelled by the tremendous
pressure and heat. It might be a perfectly round object to begin with.
But as it moves upward it must pierce all that is the earth—the water,
the slate rock, the heavy rocks, the various layers of soil. Meanwhile,
Nature keeps pushing it up, putting pressure on it—and when you put
pressure on anything over a period of a million years or so you begin
to dent it—so that the rounded rear of that diamond is put out of shape
and with pressure from two sides it becomes
(8)
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