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Eric C. Emms, FGA DGA Ltd
07973 725 266 34 Ely Place, Suite H 4th Floor, London EC1N 6TD, UK
| Eric writes non-technical gem-related articles for gem industry publications. See the menu on the left for a list of a few published in the past. The following are two recent examples: Diamond,
Si A simulant of diamond is a stone that looks like diamond but has different chemical properties (unlike diamond not made up of carbon atoms), physical properties (dissimilar values for hardness, density and thermal conductivity to diamond) and optical characteristics (e.g. lustre, refraction and dispersion). Common simulants
are synthetic cubic zirconia, usually referred to as CZ or sometimes as
“cubics”, a very cheap but effective imitation composed of zirconium
dioxide; and synthetic moissanite, an increasingly popular manufactured
stone. Other less common simulants may be encountered, such as colourless
synthetic spinel, YAG and GGG (good simulants sold in the 1970s prior to the
mass marketing of CZ) and glass, found in most costume jewellery, sometimes
called paste. So what to look for with a jeweller’s lens? Examine both the surface and the interior of the gem. Diamond is the hardest known material so when cut and polished takes an extremely flat surface. Where two facets meet (say a star and a kite facet) the edge will be extremely sharp. Facets seen on simulants have more rounded edges. Keep a CZ and a moissanite sample and regularly compare each with a diamond. It may take a while to practice this identification technique and once mastered is extremely beneficial. Take note that
diamonds exposed to a great amount of wear over the years may show abrasions on
their sharp facet edges. Such abrasions are seen commonly on old cut gems (old
English and old mine brilliants) and should not be taken as evidence of the gem
not being a diamond. Moissanite is a pretty hard simulant so the rounded facet
edges are harder to discern although I find moissanite is easier to spot than
CZ. Moissanite, unlike the other simulants mentioned above, exhibits double
refraction. Just look for a doubling of images (say the pavilion facets meeting
at the culet) when examining moissanite through a kite facet. To my eyes
moissanite of appreciable sizes (say over half carat) show a tell-tale yellowish
green colour. Most simulants tend to being ‘loupe-clean’: no inclusions are
noticeable using a lens whereas most diamonds contain crystals, feathers, and
clouds etc, inclusions an experienced eye readily identifies. You should be
aware of gem quality synthetic diamonds being sold in the You should be aware that synthetic diamonds exist, know how they can be identified and how to describe them to a consumer. Please contact us for information of diamond courses we run. The
New
Gemmology Whenever I present
a coloured stone seminar or a short practical diamond grading course there is
normally at least one participant who has never held a loose precious stone in
their hand. Following their initial excitement in handling the gem, usually in
the form of gasps of approval and much moving of the gem to catch the light and
admire the full beauty, one of two questions (or both) normally is asked of me:
“Is it real?” and “How much is it worth?” These two primary questions
reveal the most emotive elements the consumer instinctively feels about gems. Let’s develop
these themes. By asking the first question the consumer, when considering a gem
or gem-set jewellery purchase, wishes to be reassured of the authenticity of the
gem: “Is it real or is it a fake?” the prospective buyer of a ruby ring may
ask. Without wishing to re-ignite continuing debates within our industry on the
precise definitions and negative consumer perceptions of the words
‘simulant’ and ‘synthetic’, it is clear to me that all of us in the gem
and jewellery industry must be able to answer fully this fundamental first
question posed by the consumer. An obvious
supportive reply to the question may be “Yes, the ruby is natural. Not a
man-made ruby or something that looks like ruby” Our response immediately
raises the gemmological subjects of accurate gem identification and unambiguous
description. We must be in no doubt the ruby is not man-made by testing the gem
ourselves, using our gemmological expertise to confirm genuineness and/or asking
a competent gemmological laboratory for a report attesting to its authenticity. So now the would-be
ruby consumer is confident the gem of interest to him or her is a genuine ruby.
(As an aside, coloured stone jewellery pieces displayed in the windows of a
retail store close to where I live in central Perhaps the ruby
has been heated, or its surface reaching fissures healed by “flux”, or any
surface cavities filled with “glass” or fissures have been filled with
“glass” or the ruby may have been stained with dye or coloured oil? Is a
ruby treated by any one of these modifications still to be described as a
“ruby” to a buyer? As an example, consider a ruby heated and its fissures
filled with glass to improve its appearance: is this modified gem still to be
thought of by seller and buyer as “natural”? Of course, we can
refer to published recommendations issued by the World Jewellery Organisation
(CIBJO), the American Gen Trade Association (AGTA), the Laboratory Harmonisation
Manual Committee (LHMC) and other authorities on what may be called a
“ruby”, a “natural ruby”, what enhancements need to be “disclosed”
and how gem laboratories may describe such treatments on their reports. But
within our industry I do not see absolute agreement on these definitions. I am,
at present, not certain what a “natural ruby” is anymore: pity the poor
consumer! When we address our
consumer’s second question “How much is it worth?” we consider the gem’s
price - so many US dollars for the stone. Yet price follows from value, and
establishing value only comes from ascertaining quality. It follows when
answering the second question we must be able to communicate effectively the
quality of a gem to the consumer. With colourless
diamonds a useful pointer to quality is the so-called 4Cs. However carat weight,
colour, clarity and cut does not convey fully the beauty of a diamond. The
brightness, dispersion and scintillation of any polished diamond cannot be
expressed in terms of the 4CS or of a “cut grade” or indeed by all the
information listed on a diamond grading report. On a personal level, I find
antique diamonds fashioned in the old mine brilliant style most aesthetically
pleasing, yet such diamonds may score poorly if judged by modern ideas of
quality. With coloured
stones quality generally can be defined best by reference to colour and rarity.
Each of us, whether we be a miner, gem dealer, gemmologist, gem valuer or
retailer, must be prepared to contribute in explaining these factors to the
would-be consumer. We need to demonstrate the wide range and depths of colour
seen in rubies and we should show the relative rarities of an untreated ruby and
the various treated rubies considered above. How best to express these factors
to the consumer? Increasingly we
must be prepared also to discuss the third likely consumer question: “Where do
you source your gems?” Gemmological
education arms us with facts so we can understand and identify the plethora of
diamonds, coloured stones, pearls and cultured pearls. The new gemmology, as I
phrase it, must go further. Gem facts and figures and correct methods of
identification are crucial for a successful basis in classical gemmology but
today we must also learn to communicate. The new gemmology will require us all
in answering actively consumer questions on gems and demonstrating authenticity
and quality of coloured stones to the prospective purchaser in an engaging and
enthusiastic manner. Do all of us have the understanding, inclination and
fervour for this important undertaking?
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