|
|
past feature
|
|
|
Conflict Diamonds
Elude Mass Spectrometry
Scientists
conclude that mass spectrometry does not
offer a solution for identifying conflict
diamonds. Conflict diamonds make up
approximately 4% of the world's diamond
trade and are used to fund rebels and
guerillas and their causes. The United
Nations has condemned the sale of conflict
diamonds some of which originate from the
Congo basin, Sierra Leone and Angola.
Geologist and mineralogists discussed ways
to characterize diamonds during two
sessions this past week at the Spring
meeting of the American Geophysical Union
in Washington, D.C. These sessions
were to followup on the request made by
President Bill Clinton shortly before he
left office to see if scienetists can
determine the geographic origin of a
diamond.
Typically, all diamonds have impurities,
but they are in the range of
parts-per-million, parts-per-billion or
even smaller. Just a few hundred
parts-per-million of nitrogen make
diamonds yellow, while much smaller
amounts of boron will make them blue.
Carbonados, or black diamonds, are used
mostly as an industrial abrasive and
contain iron and copper. Except for these
slight impurities, diamonds are made up of
carbon and are the hardest known natural
material on Earth.
The trouble is diamonds all come from deep
inside the earth, so any chemical
signature will reflect their origin over a
hundred kilometers under the surface. And
many of the conflict diamonds come from
alluvial deposits formed when stones are
washed away by water and weather such they
could be moved miles from their geological
origin.
Peter Heaney, an Associate Professor of
Geoscience at Pennsylvania State
University, and Dr. Edward Vicenzi of the
Smithsonian Institution, tried to see
whether a mass spectrometer and a
transmission electron microscope could be
used to characterize minuscule pieces of
diamond removed from gemstones to
determine their origin. "Most
crystals have structural mistakes such as
missing rows or layers," says
Heaney. "Different locations may
have different defect assemblages so that
we can associate diamonds with their
original locations." The ratios of carbon
isotopes in diamonds were also
studied.
"It takes very sophisticated equipment to
measure these things in diamonds," says
Heaney. "Using current methods, it
is not possible to screen out conflict
diamonds because it would be very
labor-intensive."
"I think the opinion of most people who
have been thinking about this today is
that practical methods have not been
demonstrated for telling where diamonds
come from," James Shigley of the
Gemological Institute of America told a
news conference.
Yet mass spectrometry could play a larger
role in characterizing diamond coatings.
The diamond industry is looking at the
possibility of applying an invisible
chemical coating on "honest" diamonds at
the source to allow a spectrographic
analysis to be made that may show where a
diamond originates. But this approach
would not allow all the diamonds already
in the marketplace to be categorised, so
that in the meantime diamonds will
continue to conceal their origins.
|
|
|
|