Pearls analysis to help determine whether they are natural or cultured

(20 Jun 2014) LEADIN:
Pearls are alluring gems that symbolise purity, status and have always been very highly prized.
But when the Japanese started producing cultured pearls early last century differentiating between the "man-made" and natural pearls became important.
Nowadays the distinction between the two has become ever more difficult as cultured pearl producers become increasingly sophisticated in imitating nature.
STORYLINE:
Pearls, nature's beauty and for centuries man's obsession.
These historic necklaces from China featured in a 2013 Victoria and Albert Museum's exhibition, which explored the history of the jewels from the early Roman Empire right up to modern day designs.
The ability to distinguish a natural from a cultured pearl used to be a simple matter.
Something that could be done by a trained eye, but with the difference in price between natural pearls and cultured pearls widening making the distinction has become more important.
In Basel, Switzerland at the Schweizerisches Gemmologisches Institute (SSEF) a professional team are employed to deal with thousands of pieces of pearl jewellery that arrive for certification - much of it very expensive.
Laurent Cartier, Project manager at SSEF explains there are a number of different aspects about which clients require clarification.
"The first one would be is the pearl natural or cultured? A second maybe be is it fresh water or salt water? So did it originate in a fresh water mussel or a salt water oyster. Then they will also want to know is the colour of the pearl is it of a natural origin or has it been treated or modified."
The less a pearl has been tampered by man with the more valuable it is.
Natural pearls are very rare and highly prized.
Specialist equipment has been developed to help scientists understand each pearl on a cellular level.
Once the pearls have been logged in and measured by hand at the SSEF headquarters in Basel, the physical examination begins using technology.
The testing starts with a machine that separate fresh water from salt water pearls.
Judith Braun head of Analytics explains that the specially developed cabinet shows that a pearl originates in fresh water by disclosing it as having a far lighter colour.
"This is an X-ray box that we have adapted for our pearl testing needs. The measurement procedure tests the pearls with 4 milli-amper and 94 kV coming from an X-ray source. This energy source may lead the pearls to react, if they are of freshwater origin then they will be bright on the image, if the pearls are of saltwater origin they will remain dark on the image." she says.
Michael Krzemnicki is a mineralogist and Director of SSEF. He says the conclusion always depends on combining the results of different tests that range from chemical analysis to 3D images.
"We have plenty of instruments which help us to conclude. It is always when it gets to a result it's always a combination of many observations and of many analytical data. So it starts with radiography, there is chemical data which we get, we have reactions on the UV light, reactions on the x-rays. We have also instruments like tomography where we see very precise internal structures in three dimensions."
In Zurich Joana Meyer who works as a researcher for the Department of Environmental System Science at the Swiss Federal Institute of Technology (ETHZ) in Zurich has been able to genetically fingerprint a pearl.
The process of obtaining a pearls DNA is complex but the results have been game changing and increased the quality of the final analysis.

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