Gifts
from the Earth:
Diamonds
Diamond
C; Pure Elemental Carbon
September, 2008 - a diamond weighing
478 carats was discovered in a mine in Lesotho, South Africa. It is
the 20th largest uncut diamond in the world. The center of the diamond
has been deemed 'perfect' and is likely to yield the world's
largest cut diamond, weighing about 150 carats and worth tens
of
millions of dollars. That would dwarf the current record-holding diamond,
the 105-carat Kohinoor in Great Britain's Crown Jewels. The largest
rough diamond found was the Cullinan, in 1905, which weighed 3,106 carats
uncut.
One of the most highly prized gemstones
in the world is diamond because of its many desirable
qualities and few weaknesses. On Moh's hardness scale (a mineral quality
used to identify and distinguish minerals) of 1 to 10 it is the only
known substance to rate a perfect 10. It is the hardest substance on
earth because of the unique arrangement of atoms within the mineral
- they are packed closer together than any other substance. Diamond
also has the highest melting point of any substance - 3,820 degrees
Kelvin. It also is an excellent heat conductor and is transparent over
the widest range of wavelengths. The qualities of a diamond that make
it so highly valuable are its broad color range (there are more than
just white or clear ones), high refraction, high dispersion or fire,
very low reactivity to chemicals, and rarity.
Diamonds are truly ancient stones
formed deep within the earth (over 100 miles/160km deep) under
extreme pressure and very high temperatures. They were brought close
to the earth's surface by brief, explosive volcanic eruptions that happened
between 1,100 million and 20 million years ago, carried in Kimberlite
pipes that were created as magma flowed through deep fractures in the
earth. The magma inside the kimberlite pipes acts like an elevator,
pushing the diamonds and other rocks and minerals through the mantle
and crust in just a few hours, without melting them or changing their
internal structure. Many natural diamonds you see today are as much
as 1 billion years old!
There is still a great deal we don't
know about exactly how diamonds are formed, but they exist at great
depths under very high temperatures and extremely high pressures. Carbon
exists in abundance in the earth and its atmosphere, but in various
forms. The most stable form of pure carbon is graphite - the substance
used as pencil lead. In fact, all diamonds in the earth that are near
the surface are very, very slowly being converted into the more stable
graphite.The natural, uncut form of pure diamond crystal comes in isometric
cubes and octahedrons (see above right).
The old saying "Diamonds are forever"
really is true, from the human perspective. There is nothing on earth
that is stronger, more durable and enduring than diamonds.
