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How To Detect Synthetic Diamonds

May 1, 1995 5:23 PM  
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Magnetic Wand Helps Jewelers Detect Synthetics

By: Alan Hodgkinson FGA, DGA

Faceted synthetic gem diamonds are poised to give the diamond

dealers and jewelry trade a headache. The remedy lies in a

magnet the size of a child's aspirin.

The Tucson Gem and Mineral Show can be relied on for its annual

store of surprises, and 1995 was no exception. One contender for

the surprise prize has to be The Hanneman Magnetic Wand, more

accurately described as a synthetic diamond detector.

In late 1994 a 2.32-carat faceted orange diamond was handed in to

the London GAGTL Laboratory for certification of natural or

treated color. The highly experienced staff identified the stone

as synthetic diamond.

How is the trade to identify such diamonds? Fortunately we are

well served by such publications as The Journal of Gemology, and

Gems and Gemology, to name but two, which keep us abreast of

developments, and through their photography, provide many visible

clues to familiarize us with the appearance of various

gemological phenomena.

Simple Magnet Gets No Response

However, mention of the magnetic properties evident in such

synthetic diamonds has little significance to the dealer or

jeweler equipped with nothing more than a domestic magnet.

Two years ago at Tucson I demonstrated a large, heavy, expensive,

samarium, cobalt, iron magnet which, by its strong magnetic

attraction, could pick up the average synthetic diamond.

After the Canadian Gemmological Association 1994 conference, I

was privately shown a new rare earth magnet by Harold Oates and

Dr. W. Hanneman. The neodymium boron iron magnet is remarkable

for its minute size (child's aspirin), extraordinary magnetic

attraction and low cost. It also retains its magnetic property

over the years.

DeBeers and Chatham Created Gems were each extremely helpful and

co-operative in the loan of faceted synthetic gem diamonds, the

Chatham stones being Russian grown. Colors studied included

yellow, orange, and colorless. Yellow diamonds were also

studied from Sumitomo.

30 Synthetics Attracted to Powerful Magnet

Most of the thirty synthetic diamonds observed responded to the

rare earth magnet, and could be picked up, provided they were not

lying table-down. Several which were not so responsive could be

attracted down the slippery surface of a glossy magazine, angled

about 30. Again, the stones should be pavilion down.

The jeweler often feels neglected by gemology, as most of the

specimens which confront him are mounted in jewelry, With this

in mind, I set a De Beers 0.39-carat yellow synthetic into a

natural diamond cluster ring. A 2" diameter circle of polystyrene

was floated in a basin of water, just sufficient in size to

support the 18 carat gold ring. When closely approached, the

whole island was attracted to the magnet, due to the inclusions

in the synthetic diamond.

Gem size diamonds are generally grown in a nickel/iron melt

which, when incorporated into the diamond structure, produces a

magnetic response in the host gem. On the other hand, natural

diamonds show no such magnetic response.

Appearance of Metallic Inclusions

The metallic inclusions in the synthetic diamonds may appear as:

a Large or small rod or lath-like inclusion. b Large or small

cube-related shapes. c Isolated pin head dots, more visible by

cross-polarized light d Dust clouds which reflect the color of

the host stone

Recent experiments have shown that there are instances of natural

diamonds responding to the more sensitive magnetic tests

indicated above. such rare occurrences occur when there are iron

sulfide inclusion (s) within the natural diamond. such

inclusions (Pyrrhotite and Pantlandite) are generally surrounded

by expansion fractures, and these fill with black sulfide films.

such black inclusions have not been observed in synthetic

diamonds to date, and their appearance is in contrast to the

clean metallic aspect of the nickel/iron inclusions in synthetic

diamond, and which so far do not show such expansion fractures.

Two yellow Sumitomo diamonds (essentially flawless) showed no

attraction to the neodymium magnet, but these exhibited the

typical reversed fluorescence to natural diamonds, i.e. they

fluoresced stronger under short wave than long wave ultra violet

light. Natural diamonds flouresce stronger under long wave than

short wave ultra violet light. Any diamond flourescing stronger

under short wave ultra violet light is synthetic.

The magnetic wand synthetic diamond detector is available from

Hanneman Gem Instruments, PO Box 942, Poulsbo WA 98370, USA.

US$12 post and packing paid to any destination.

Mr. Alan Hodginson is a world-recognized gemological expert and

noted lecturer from Scotland.

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Tags: De Beers, Gem Diamonds, Jewelry
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