Last week”s column concerned Hedy Lamarr, a glamour queen of
the 1930s and 1940s. Later, another sex symbol, Marilyn
Monroe, sang a song about diamonds being a girl”s best friend.
A few weeks ago I watched a Nova program on Public
Television and sure enough, a film clip of Marilyn”s song was
included. (I just saw the same film clip on “Sunday Morning”.)
You”re right in surmising that the Nova program was about
diamonds. The DeBeers hold on the diamond market has existed
for well over a century. That virtual monopoly is what keeps the
supply and demand for diamonds under control and allows the
gems to maintain their value. In several of his Hott Spott
columns, Brian Trumbore has written in depth about the DeBeers
history and concerns that Russia may jump ship and sell outside
the DeBeers market. Russia could flood the market with
diamonds, undercutting the price and destabilizing the whole
diamond market.
One reason that Russia can threaten the stability of the diamond
market is that Russia has diamond mines of its own, the output of
which Russia has been selling to DeBeers. Along with other
countries doing the same thing, this has allowed DeBeers to dole
out diamonds as the market demands. But there is another
potential problem of concern in Russia. This was the subject of
the Nova program – synthetic diamonds. It”s hard to tell, at least
for me, whether some of the sparkling jewelry adorning women
today contains real diamonds or the fake stuff. A jeweler, of
course, would have no problem distinguishing diamonds from
today”s lookalikes, which are completely different materials.
These lookalikes are typically cubic zirconia or moissanite and
are not synthetic diamonds. They are chemical compounds, not
simply the element carbon. As we”ve discussed on a number of
occasions here, diamond is just plain carbon, the same carbon
that is the graphite in your “lead” pencil. We”ve talked about
graphite having a layered structure with the bonds between the
layers being so weak that the graphite easily slides layer by layer
onto your sheet of paper as you write. In graphite, each carbon is
bonded strongly to three other carbons in the layer.
In diamond the carbon is not layered but each carbon is bonded
to four other carbons in a very stable structure; hence its
hardness. The hardness of diamond makes it extremely valuable
as an abrasive for cutting tools. I used diamond-coated wheels
daily during certain periods of my Bell Labs career to cut glass
or quartz tubing for my experiments. The small diamond chips
are bonded to the wheel, which rotates like a rotary bench saw
used to cut wood.
The Nova program traced the history of synthetic diamond back
to the days of World War II. Industrial diamonds for cutting
tools to fashion such items as airplane parts were critical to the
war effort. Sources in South Africa were deemed unreliable due
to submarine warfare and other aspects of war. Accordingly, an
effort was funded to try to grow synthetic diamond. It was well
known that diamond is the stable form of carbon at very high
pressure. The problem was how to take ordinary graphite and
put it under high pressure and make it convert to diamond. Not
only was high pressure needed, but also a high temperature was
required to loosen the carbon bonds so the carbon atoms could
rearrange themselves into the diamond structure. Two General
Electric scientists, H. Tracy Hall and Herbert Strong, were
assigned to the task and they went to work. They squeezed and
heated the graphite for several years without any success. Those
bonds of the carbons in the layers of graphite just wouldn”t be
broken.
Stymied, they decided that the only way to accomplish the task
was to dissolve the graphite into solution. They hoped that
would break up the graphite structure and the carbon atoms
would be free to move around and then precipitate out of solution
in the diamond form at high pressure. This approach may have
been prompted by the finding of fine diamonds in the awesome
impact crater of that meteorite in Arizona. Those tiny diamonds
were found in connection with a metallic ore. The feeling was
that the metallic ore had melted and dissolved the carbon. Hall
and Strong added some metallic stuff to the graphite in their high
pressure, high temperature machine and, Voila! Tiny crystals of
diamond were formed.
Some years later at Bell Labs, I had two brilliant ideas. One was
to try to make diamond by passing benzene or some other
organic vapors over a diamond seed crystal. The idea was to
trick the carbon atoms into growing on the seed diamond even
though that was not the stable form of carbon at ordinary
pressures. It didn”t work. However, John Angus at Case
Western carried out a similar type experiment but with hydrogen
added. What do you know? Diamonds! So much for my idea.
My second brilliant idea was to take a diamond seed crystal (it
only cost about twenty bucks), seal it in a quartz tube with some
graphite and some tin. I then put the tube in a furnace positioned
so the top of the tube was hot and the bottom at a lower
temperature. The idea was that the tin would melt, the graphite,
which floats in tin, would dissolve and travel down to the cooler
seed at the bottom of the tube. Because the graphite is less
soluble at the lower temperature, the carbon would precipitate
out of the solution and would be tricked into growing on the seed
as diamond. It turned out my diamond seed dissolved! Another
brilliant idea down the drain.
So, what did I see on the Nova program? Would you believe that
this Russian, Boris Feigelson, and his colleagues are putting
graphite in a vessel with some kind of molten metal and they
have a diamond seed at the bottom. The only thing different
from the experiment of yours truly is that they have this vessel in
a pressure chamber. And what happens? They grow gem
quality diamonds of a carat or more! Look out DeBeers! When I
saw this on Nova, I must admit to uttering a “Damn!” However,
I consoled myself with the fact I didn”t have a high-pressure
system to perform such an experiment.
The only problem with their first diamonds – they were yellow!
Obviously, DeBeers breathed a sigh of relief. It would be easy to
tell diamonds mined from nature from these synthetic diamonds
just by looking at them. But then the reason for the yellow color
was determined to be something quite simple – nitrogen in the
diamond. In the light emitting diode business at Bell Labs, we
used nitrogen in gallium phosphide to give us green light, a good
thing. It turns out that in nature, over a period of millions or
billions of years, the nitrogen atoms gradually move around in
the diamond and clump together. When the nitrogen atoms
clump together they no longer give a yellow color. At GE they
showed that the synthetic yellow diamonds could be made less
yellow by heating for prolonged periods. However, the time
required to get colorless diamonds would be prohibitively long
and the process would be too expensive. DeBeers is happy!
Obviously, the way to get rid of the yellow color is to get rid of
the nitrogen. In the semiconductor game we often worked with a
principle known as “gettering” to get rid of an unwanted
impurity. This would typically involve using a metal, usually a
liquid metal, that would getter, or gobble up the offending
element, often copper in the early days. Wouldn”t you know, the
Nova program says the Russians have added aluminum to their
secret solvent and the aluminum acts as a getter by reacting with
nitrogen. Result – colorless diamonds! Now DeBeers is really
sweating!
In the program, the background music at this point was Henry
Mancini”s theme from “The Pink Panther”, appropriate for the cat
and mouse game going on between DeBeers and the Russians.
With colorless synthetic diamonds, the question is how to tell
them from the natural ones. The DeBeers counter sleuths have
indeed come up with a method using ultraviolet light of a certain
frequency and intensity. The synthetic diamonds glow under this
wavelength light while the natural diamonds stay dark. When
the UV light is turned off, the synthetic diamonds phosphoresce.
That is, they continue to glow for a several seconds. Advantage
DeBeers.
Why do the synthetic diamonds phosphoresce? Without going
into detail, it”s related to how the crystals of diamond grow.
This growth property differs in nature from the property found in
the synthetic diamonds. Naturally, the Russians are working on
this problem. Another complication for DeBeers – an American,
retired general Carter Clarke, heads a company that has invested
in the Russian technology. He was interviewed on the Nova
program and posed a very appropriate question. If a woman has
a choice between two pieces of diamond jewelry, one containing
very expensive natural diamond and another, identical but much
cheaper piece containing synthetic diamond, which will she
choose? Remember that the only difference will be that the
synthetic piece will phosphoresce under UV light. General
Clarke is betting that the choice will most often be the synthetic
choice.
The above example is obviously a sexist one. Males must also
buy a fair amount of jewelry, mostly for the ladies I would
presume. Would a male be intimidated by the possibility the
recipient of his gift might have a UV light source handy? What
would your choice be? The fate of the world diamond market
and the value of all your precious jewelry could depend upon it!
Allen F. Bortrum
