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it
solidified into blue ground, or kimberlite, where the precious rough
is still found today. The durability of a gem depends on both its
hardness and toughness. Diamond, although highest on the scale of
hardness (rated 10 on the Mohs scale), is not as tough as some gems
because of its good cleavage
(Cleavage is the tendency of a diamond to
split in certain directions where the carbon atoms are furthest
apart.) Diamonds have a very high degree of transparency, refractivity
and dispersion or 'fire' which gives rise in cut diamonds to a high
degree of brilliancy and a display of prismatic colors. A diamond's
fiery brilliance makes it cherished above all other gemstones by the
majority of people.
Diamonds occupy a position of
incomparable demand. Beautiful and rare, diamonds are desired for
their sparkle and message of love. When you buy a diamond there are
four points that you should consider, collectively known as the Four
C's. Cut: Refers to the symmetry and proportions of the stone; it is
what gives the diamond its sparkle. There are many diamond shapes to
choose from. Whatever shape and quality you prefer; a Laboratory
Report should be a requirement for your engagement ring or any
significant diamond purchase.
Color: The most desirable diamonds are
colorless. The best color is D, which is almost clear white; the color
scale descends from there through the alphabet toward Z, moving
further away from colorless toward yellow or brown tints. Clarity:
Diamonds have small imperfections in them known as inclusions; the
fewer inclusions, the more valuable the stone. Carat Weight: This is
the size of the stone. The word carat comes from the carob seeds that
were used to balance scales in ancient times. DIAMOND.
The mere mention of the word fills the
mind with a multitude of concepts and images. Diamond is a mineral, a
natural crystalline substance, the transparent form of pure carbon.
Diamond is something superb, the peerless "king of gems"
that glitters, dazzles, and symbolizes purity and strength. Diamond is
for engagement and the 75th wedding anniversary, for a commitment to
never-ending love. Diamond is indomitable, the hardest surface known.
Diamond is exotic, formed in Earth's interior and shot to the surface
by extraordinary volcanoes. A diamond is likely the oldest thing you
will ever own, probably 3 billion years in age, fully two thirds the
age of the Earth. Diamond is a strategic and high-tech super material
for our technological society. Diamond is a shape. This exhibition
presents the fascinating story of the nature of diamonds.
There are some, including the former
writer of this that make light of strain in diamonds. It is also
called Stress and occurs in about 40% of diamonds. It is generally
more prevalent in pears, triangle shapes and marquise shape cut
diamonds than in rounds. To a cutter strain is of severe importance.
Any cutter worth his salt will analyze the location, color and amount
of the strain before cutting a diamond. Strain sometimes also if
evident around an inclusion in the stone and shows up with tension
marking, which sort of has an appearance of a circle with a cross. Is
strain something to be "terrified" of? No it isn't.
Industry perception is that if the
diamond crystal survives the cutting and polishing process it will
survive normal wear and tear. However being armed with the information
is important to know. Diamonds are the most coveted of all precious
gems, as is witnessed by the extremely high demand for them. While
this has not always been the case, diamonds are nonetheless exquisite
gems that go through a long, tedious refining process from the time
they are pulled from the ground to when you see them in the jewelry
store. And, while some of the mystique of diamonds may be gone --
they're just carbon, after all -- the diamond will likely continue to
be a highly coveted jewel, because, well, "A Diamond is
Forever."
Physicists in Germany have created a
material that is harder than diamond. Natalia Dubrovinskaia and
colleagues at the University of Bayreuth made the new material by
subjecting carbon-60 molecules to immense pressures. The new form of
carbon, which is known as aggregated diamond nanorods, is expected to
have many industrial applications (App. Phys. Lett. 87 083106).
The hardness of a material is measured
by its isothermal bulk modulus. Aggregated diamond nanorods have a
modulus of 491 gigapascals (GPa), compared with 442 GPa for
conventional diamond. Dubrovinskaia and two of her co-workers - Leonid
Dubrovinky and Falko Langenhorst - have patented the process used to
make the new material.
Diamond derives its hardness from the
fact that each carbon atom is connected to four other atoms by strong
covalent bonds. The new material is different in that it is made of
tiny interlocking diamond rods. Each rod is a crystal that has a
diameter of between 5 and 20 nanometres and a length of about 1
micron.
The group created the ADNRs by
compressing the carbon-60 molecules to 20 GPa, which is nearly 200,000
times atmospheric pressure, while simultaneously heating to 2500
Kelvin. "The synthesis was possible due to a unique 5000-tonne
multianvil press at Bayerisches Geoinstitut in Bayreuth that is
capable of reaching pressures of 25 GPa and temperatures of 2700 K at
the same time," Dubrovinskaia told PhysicsWeb.
The Bayreuth team measured the
properties of the samples with a diamond anvil cell at the European
Synchrotron Radiation Facility at Grenoble in France. These
measurements indicated that ADNRs are about 0.3% denser than diamond,
and that the new material has the lowest compressibility of any known
material.
In addition to working out why the new
material is so hard, the Bayreuth team also hope to exploit its
industrial potential. "We have developed a concept for innovative
technology to produce the novel material in industrial-scale
quantities and now we are looking for partners in order to realize our
ideas," said Dubrovinskaia.
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