How To Detect Synthetic Diamonds
May 1, 1995 5:23 PM
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
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.
De Beers, Gem Diamonds, Jewelry