Scottish Gemmological Association
Synthetic Moissanite, Diamond
and some distinctions
by Alan Hodgkinson
Uploaded to the SGA Website on January 17th 2010
(Click on thumbnails to view pictures. Close the
window to return to the text.)
Other diamond simulants are not included, as they are too rarely met
with, far too soft, or do not pose a sufficiently diamond-like identity.
Synthetic diamond has the same optical properties as diamond and cannot,
therefore, be distinguished by the methods discussed in this article.
* The numerical values for "luster" are taken from the table of "Hanneman
Relative Luster Values", Summer 1977, Gems and Gemology, pages 302 to 305,
and are easily demonstrated on the Hanneman "Diamond Eye" (see Fig.
3: Relative Hardness
synthetic ruby shows scratch marks on the table facet from moissanite because
the hardness of this silicon carbide material (9+) is greater than corundum's
(9) on the Mohs Scale of hardness. Hopefully this will see an end to such
a test, formerly deployed by some for identifying diamond (10).
4: Thermal Probe
5: Double Refraction
culet invariably appears singly refractive through the table facet, while
the refracted image of the culet region shows double refraction when seen
through the main crown facets, as here. The occurrence repeats under 8
of the main crown facets as the stone is manoeuvred.
With such evidence, it is more than obvious to any thinking gemmologist
that here is a birefringent mineral, which distinguishes itself from diamond
by a x10 loupe. "What's the problem?" I hear you ask.
Yes, but what if your loupe has been borrowed by another member of staff
at the critical moment of examination?
The Hodgkinson Method separates the two, even in the dark, without
looking at the stone, without touching; even if mounted, without instrumental
aid other than a flashlight torch. Even a candle or the moon will
suffice, if available!! What's more, it's good for the soul of a
keen and enthusiastic gemmologist, but make sure you get your loupe back.
The next problem may not be so easy.
6: Table Reflection Doubled
further down just below the table reflection, the star facets come into
view, and these also show "doubled" outlines. Features in Figures 6 and
7 are shown in Gems and Gemology, Winter 1997, page 268
8: Obvious Dispersion
high dispersion (0.11) is apparent in this larger moissanite (1.26ct) and
readily distinguishes it from diamond (dispersion 0.04) in this size of
9: Dispersion Missing!
dispersion (fire) distinction of moissanite from diamond is not outwardly
evident to the eye in small stones, especially when set in an eternity
ring for instance, and even less so if the stones are not clean. The eternity
ring is set with small, princess cut synthetic moissanites. Set in jewellery,
these newcomers will present a problem for the jewellery trade once they
start returning to jewellers' shops for various services, especially after
day-to-day wear, when the pavilion surface becomes "organic"!
Synthetic moissanite will help force the pace of more and better staff
training in basic gemmological skills. The eternity ring (courtesy Jeff
Hunter and Howard Rubin) was easily distinguished from diamond by raising
the ring to the eye and observing its "Visual Optics" performance - see
Figures 29 and 30.
seen in moissanite are fine hair-like inclusions reminiscent of "silk"
in Sri Lankan sapphire. Though not all parallel, there is a general direction
to their arrangement which follows the "c"-axis.
11: Criss-cross and "Morse Code Silk"
some moissanites the silky inclusions bifurcate, some stop and start along
their length, some angle at one point and then resume their original direction
(geniculate fashion). All the silky variations mentioned would seem to
be fine tubular versions of those in Figure 12.
Some of the silky inclusions featured here have a similar aspect to
the diamond photomicrograph featured by John Koivula on page 72 of "A photolexicon
of inclusion related terms for to-day's gemologist". Canadian Gemologist,
Autumn 1998, pages 67 to 74.
rod-like inclusions are simply coarser versions of the silk in Figure 11,
and they are, in fact, tubules, as can be seen where they come to a facet
surface. Some of the tubules also bifurcate. In the main, again,
many of these tubules are parallel to the "c"-axis, or nearly so.
It should be borne in mind that the repertoire of inclusions in diamond
is vast. They can mimic the appearance of inclusions in other gem
materials, so one should always be cautious when evaluating inclusions
with a x10 loupe. See Fig. 42.
13: "Bicycle Wheel"
are so many tubules in this stone that they appear (by reflection across
the pavilion) similar to the spokes of a wheel. In fact the tubes correspond
closely to the "c"-axis, although this is not apparent from the photo.
14: Solid Inclusion
smoke-like structure flows from what appears to be a crystalline inclusion.
stone seen has interesting surface marks resembling creases. As these were
continuous across several facets, it was presumed they were similar to
grain lines in a diamond, which represent hardness/softness boundaries.
In one zone the lines were continuous, while in an adjacent zone they were
discontinuous dots and dashes with "morse code" appearance.
16: Cubic Inclusions?
crystal inclusions in a brownish/yellow moissanite were so compact in form
as to suggest crystallization in the cubic system.
17: Electron Microscope View (Courtesy Dr. Placido,
of the inclusions in Figure 16 showed silicon, carbon and vanadium to be
present. This, and the compact form of the inclusions, suggest the beta
form of silicon carbide which is isotropic, but this is only speculation.
The vanadium may derive from the petroleum used in the synthesis being
rich in the fossil remains of the shrimp-like creatures - holothurian-
which store vanadium in their blood. This suggestion came from Dr. J. Nelson,
who had experience in growing silicon carbide crystals circa 1948.
18: Diamond Ultra Violet Fluorescence
shows typical sky-blue fluorescence of a cape series diamond under long
wave ultra violet light. A brown series diamond alongside fluoresces greenish
Moissanite Ultra Violet Fluorescence - Long Wave
The thirty-five colourless moissanites tested (courtesy Moissanite UK
Limited) appear to fall into one of two colour grade categories.
a) greenish grey specimens which fluoresce a cinnamon orange shade.
b) yellowish cape series which show little observable fluorescence.
N.B. Occasionally diamonds are seen fluorescing in a similar cinnamon
colour under UVLW.
UVSW. The moissanites tested by the writer showed little observable
fluorescent response to short wave UV light.
Research Director Dr. Mark Kellam at C3 Inc. took a piece of colourless
synthetic moissanite crystal which showed little UV fluorescence.
After cooling in liquid nitrogen, the material fluoresced a very visible
orange under the ultra violet lamp.
UV Fluorescence - other possible identities
Though not often seen, GGG fluoresces a dull orange under UVLW.
However, it responds unusually with an even brighter yellowy orange under
UVSW, and there is a lingering brown colour to the stone. This is
not phosphorescence. The brown tinge finally disappears, but is aided
to do so by slight heat.
The green and dark bluish black specimens are all electroconductive.
Colourless to near colourless specimens vary in their electroconductive
response. Some of the yellow tinged stones showed electroconductivity.
So far I have not seen one of the greenish grey moissanites conduct, and
would welcome any contradiction of this observation.
19: Colour Grades
row of stones shows a central "F" colour diamond of 1.00ct with three smaller
moissanites on the left having a "cape" series aspect. On the right of
the diamond are seven smaller moissanites with a slight greenish grey cast.
top spectrum of diamond shows a distinctive 415nm line, as observed in
many natural diamonds. Lesser strength lines may or may not readily show
in the region. The lower spectrum of moissanite shows the cut off from
approximately 425nm. The spectra on the left are by diffraction. The spectra
on the right are via a prism spectroscope.
21: Ultra Violet Probe
The "C3" strategy is that, when a thermal probe indicates diamond,
the stone should then be tested with the ultra violet probe to distinguish
between diamond and moissanite. Objections have been voiced that
the UV probe does not always work. Dr. Kurt Nassau responds that
the probe does always work, though the result is aided by moving the probe
tip about over the facet surface.
As an afterthought for the keener gemmologists, cassiterite (colourless
and browns) will also register as a diamond on a thermal probe, and identify
as a moissanite on the UV probe. The cassiterite RI is 2.0 - 2.1, Dispersion
0.07., DR of 0.1, which is twice that of moissanite's 0.04.
Keep an eye open, as they both appear in yellowy/orangy/brown shades
of colour as in Fig. 2. Visual Optics readily picks out the main primaries
of the lower refractive cassiterite. In fact they are rather reminiscent
of zircon, Fig. 32.
22: Japanese "Culti", Coloured Stone Checker
chance I have one of these instruments, and switched it to its UVLW transmission
test facility. The stone immediately registered positive for diamond, but
gave no reaction to the synthetic moissanite, as could be anticipated from
the absorption spectra at Fig. 20.
For those with such an instrument, there is a provision for distinguishing
emerald, ruby, sapphire and alexandrite from some of their synthetic counterparts.
Needless to say, there is no setting for synthetic moissanite. After some
experimentation, the distinction between diamond and synthetic moissanite
could best be achieved by turning the instrument to the "emerald" setting,
though the sapphire setting also provided an instant separation between
the two. The Culti will not cope with tiny gems, nor smaller set stones,
as can the C3 590 probe.
It is five years or more since I last used the Culti coloured stone
checker, but it is interesting to find that the instrument stood by its
principle design function, by distinguishing moissanite from diamond.
23: The Hanneman Diamond Eye
Hanneman Diamond Eye, is a reflectivity meter, which creates a scale
sequence of reflection. This is comparable to the refractive index
order. The inventor described it as a "Lustermeter" in Gems and Gemology,
Summer 1977, p302 to 305. Even then, the 1977 article mentioned the possibility
of identifying, or eliminating, silicon carbide.
No contact liquid is required, and the instrument copes with gems refracting
as high as diamond, rutile or synthetic moissanite. The instrument was
devised in the 1970s to cope with the contemporary threat of YAG
For those with earlier Diamond Eye models, which are not marked for
moissanite, the friction fit plastic hood lifts off carefully to allow
code "5" to be added for synthetic moissanite, beyond diamond (code
number "4") as shown in the photo. Similarly in the 1980s an "x" could
be added to mark the CZ position on the scale of earlier models.
A similar, but more expanded version, called "The Jeweler's Eye" includes
two separate scales, one for a fuller range of higher refractive gems,
and a lower scale for those gems under RI 1.8. The lower scale cannot,
of course, compete with the information obtained from a refractometer.
The Diamond Eye can be hindered by jewellery settings and is, therefore,
sometimes restricted to larger mounted stones. The C3 590 Probe is not
restricted in this way, but both instruments also have a wider gemmological
role to play.
STOP PRESS Dr Mark Kellam has been researching ways of changing the
surface structureof synthetic moissanite. As a result he has been
able to change the reflective power of the surface. The change can be doctored
to record any surface reading as low as quartz and less. C3 inc have
kindly given me a one carat altered synthetic moissanite which reads daimond
on a reflectance meter. Such an alteration could be disconcerting
if it were not the fact that using the Hodgkinson method, the difference
between diamond and moissanite is instantly seen as shown in Figures 29
Reflectance meters and refractometers work only on the surface presented
to the instrument. Visual optics literally sees through the stone to reveal
the truth of the body of the stone
24: Comparative Density and Optical Relief
set-up shows a glass cell containing methylene iodide, (SG 3.3). The moissanite
(SG 3.2) can be seen floating. At the bottom from left to right can be
seen a submerged diamond (SG 3.5), YAG (SG 4.5) and CZ (SG 5.7). This is
described as "Density Separation".
Simultaneously it is seen that the optical relief, when submerged in
this liquid, is directly related to the difference between the RI of the
stone and that of the methylene iodide (RI 1.74). The most obviously visible
stone in the immersion fluid is the floating moissanite (RI 2.69, refractive
index difference 0.95), followed by the diamond, bottom left, (RI 2.42,
RI difference 0.68), then CZ, bottom right, (RI 2.17, RI difference 0.43).
Finally the YAG which, with an RI of 1.83 and RI difference of 0.09, is
A colourless synthetic spinel would completely disappear in the liquid
due to its RI of 1.73, very close to that of the methylene iodide (RI 1.74),
an RI difference of 0.01.
25: Conoscopic Observation
conoscope reveals a uniaxial figure on the polariscope. This rules out
diamond, but does not, of course, prove that the stone is moissanite (zircon,
rutile, cassiterite and lithium niobate, etc. would do the same, as they
are also uniaxial positive, as it happens).
The figure tends to be "scrambled" by the excessive brilliance of the
stone due to its high refractive index, but it can still be made out quite
simply. The figure is seen more easily the smaller the concoscopic sphere.
Such a small sphere requires magnification to see the figure. Dr.
J. Nelson showed me a small telescopic device which sits atop the analyser
for that purpose. A microscope or x10 loupe will also help resolve
Such a diagnostic feature can invariably be seen even though the stone
is set in jewellery, because moissanites are usually cut with the table
perpendicular to the "c" axis of the crystal.
Rotation of the moissanite on a polariscope will, of course, provide
the fourfold contrasting illumination/extinction response. This alone
is sufficient to indicate double refraction and thereby rule out diamond.
The effect is generally seen through the girdle, so this will pose a problem
with certain mounted stones.
26: Optical Sign
means of a mineral accessory plate, such as mica, gypsum or quartz wedge
inserted above the stone, it can be shown that the stone has a positive
sign. In this case, the two dots, which represent the ordinary and extraordinary
rays, line up across the direction of the introduced mica plate to indicate
uniaxial positive. An inexpensive substitute accessory plate is available
for this purpose and sold as the "Hanneman/Daly quartz wedge simulator".
27: Visual Optics
It is actually easier if the stones are set, as the finger tips can
hold the side of the shank or whatever. Incidentally the pattern for strontium
titanate is similar to moissanite, but even more diffused. The softness
of strontium titanate (5 on Mohs Scale), and its lack of double refraction,
easily separate it from the hard moissanite.
31: B/D Ratio
high RI 2.7, and the optic axis at right angles to the table facet make
it awkward to locate the double refraction by Visual Optics. The photo
which captured a doubled image was obtained through the girdle area of
the stone while looking towards the light source. It will be seen that
the B/D ratio is just under half (i.e. DR 0.04 divided by dispersion 0.10
= 0.40). This means that the doubled spectral images are never separate.
32: Zircon (high type)
The B/D ratio is the brainchild of Dr W (Bill) Hanneman, as described
in the book and video mentioned. More recently Dr. Don Hoover has written
a very in-depth article on the "Hodgkinson Method" in which he explores
the whole B/D area very fully - see Australian Gemmologist 1998 Vol. 20,
"Primaries" in synthetic moissanite
Large main pavilion facet Primary images are lacking in faceted
moissanite and well proportioned round diamond, though they are seen in
CZ Fig 28 and zircon Fig 32. This is simply because the high refractive
power of the first two mentioned will not permit the light to pass through
the pavilion as refracted "Primary" images. The high
RI causes the light from the small girdle facets to bounce about within
the stone in the form of small "Primaries and "Secondaries".
Wishing to produce such a large primary image in moissanite so
that optical measurements could be undertaken, I asked Doug Morgan to cut
me a shallow prism to replicate the function of the pavilion in a faceted
gem. Successive experimental cuts were attempted to enable the light to
pass through, but it was not until the prism (pavilion) angle was 30o,
that the light could pass and a complete primary image could be examined.
From the previous paragraph it will be seen that the cutters of moissanite
could achieve a useful economy. At the moment, the larger sizes of moissanite
(above 8mm) are rare. Cutting the stones with a shallower pavilion would
mean a wider stone from a shallower crystal. The resultant stone would
still have the brilliance of a diamond, even at a pavilion angle of 35o.
In a diamond, this would present a very "fisheye" stone.
Earl Hines controls the cutting and polishing of moissanite at The
North Carolina plant of C3. He is at pains to design such cuts of
the material as will show off its optical power to the full.
33: Primaries in a brilliant cut diamond
large main "Primaries" are not seen in a brilliant cut diamond because
the high RI of diamond and synthetic moissanite block them off by total
internal reflection. The facets captured in Fig. 33 are in fact such
"Primaries". How were they captured? In 1984 Dr
J Nelson of London built a Pavilion Facet Fingerprinter, a gem projection
instrument which achieves three benefits:-
a) every pavilion facet can be plotted;
b) enables teaching of the Hodgkinson method;
c) allows comparison of one gem variety's optical
behaviour with that of another gem variety.
To overcome the total internal reflection of higher refractive stones,
Nelson immersed the stones in benzyl benzoate at RI 1.57. This enabled
the primaries to be observed, even though they are normally beyond reach
by Visual Optics.
Here a diamond displays its primaries in baby oil, RI 1.47.
while Water, RI 1.3, works equally well. The baby oil recommendation
comes from geologist, Pat Daly, and makes a much safer fluid for general
horizontal microscope study of gemstones. Note how the diamond dispersion
of 0.044 is virtually unnoticed.
34: Primaries in a brilliant cut synthetic moissanite
the same conditions as diamond in the previous Fig. 33, the higher dispersion
of synthetic moissanite, approximately 0.10, shows an extraordinary display
of technicoloured dispersion. This is yet another way to separate
diamond from synthetic moissanite. See Fig. 43 for diamond parcel
35: Heat resistance
synthetic moissanite has remarkable heat resistance, due in part to its
excellent thermal conductivity, it can withstand temperatures higher than
diamond. Consultant to C3 Inc., Howard Rubin, explained to me that the
stones can in fact be set in a wax model such as an eternity ring, then
cast in 18ct gold . The gold casting emerges with the stones already set
in situ, which offers a great saving in time and trouble, especially for
channel set or rubover settings.
An 18ct gold ring has been melted on a black charcoal block.
The synthetic moissanite placed in the molten gold immediately turns yellow.
The gold melting temperature is approx. 900oC
36: Retipping (Repronging) a synthetic moissanite
18ct white gold ring mount was rescued from a gold scrap box, and set with
a 5mm synthetic moissanite. One claw was deliberately broken off, and a
large 18ct. gold retip applied purposely. No heat guard agency was employed,
and no damage to the stone resulted.
Diamond would be damaged by such a procedure, unless care was exercised
along with a recognised heat protection agent, e.g. boric acid and
alcohol (USA) or borax and water (UK).
37: A heat damaged diamond
marquise cut diamond has been completely ruined by careless use of excess
heat in a claw repair operation. A skilled jeweller would have controlled
the gas torch so that the temperature was restricted. If not taken
from the setting, a suitable heat guard should be applied to the diamond
to protect the stone from the heat. The trade variously refers to such
a damaged diamond as "smoked", "burnt", "milked" or "fired".
38: A heat damaged synthetic moissanite
it is possible to burn the surface of a moissanite in a jewellery workshop.
However, this was only achieved by melting 18ct gold, fluxing with borax
and retaining the stone in the molten gold for three or four minutes.
Such exceptional treatment would not be met with in a casting or retipping
operation. A diamond would simply not survive.
39: CZ damaged by workshop retip operation
would normally shatter under the heat of such an operation, as here, which
makes it troublesome for various jewellery repairs. Sustained workshop
torch heat to CZ can actually turn the stones to various orangy shades,
which remain permanent.
Facets and girdle
Any attempt to pre-empt the distinction of diamond from synthetic moissanite
on the grounds of the facets, or the girdle, is liable to mislead those
who are faced with such identification in the future. Facets are as good
as the facetor. While the facet edges of a poorly cut moissanite
will show a "roll over" effect normally unseen in diamond, the facets of
a non-diamond such as CZ, or even more so moissanite, can be "diamond sharp"
if in skilled hands, and time allows.
A diamond girdle can be rough ground, smooth ground, faceted or polished
(the latter an invention of the British diamond cutters - Monnickendam).
There is of course nothing to stop a gem cutter faceting or polishing a
synthetic moissanite girdle. C3 Inc. are polishing moissanite girdles
to gain even more life from the stone, as is the aim with diamond.
we are taught that "bearding" on the girdle of a diamond is a derogatory
feature, the fact that it is unique to diamond makes it a useful identifying
observation. This is what I term a "commercial gemmological clue", that
is economic factors of time and cost make bearding more and more likely,
and it will instantly separate diamond from moissanite or CZ. A great
many round diamonds afford this clue to-day.
41: "Cups and Saucers" on the facet edges of the
microscopic feature (x56) is often seen on synthetic moissanite and
CZ, and stems from the brittleness of the material in response to the girdling
(bruting) operation. Improving awareness and technique are overcoming
42: Deceptive Inclusions in diamond
would be easy to jump to conclusions and class these parallel lines as
being similar to the tubules in synthetic moissanite Fig. 12.
Diamond Parcel Testing
Faced with a number of diamonds in a stone parcel, the question arises,
"Are they all diamond, or are there any moissanites, or CZ?"
Imagine a parcel of 300 diamonds salted with, say, 3 moissanites.
Imagine a tennis bracelet of 40 diamonds with a moissanite rogue.
Imagine a parcel of 300 moissanites salted with, say, 3 CZs.
43: Tables Down
the Nelson Fingerprinter, round stones lying table down cast their primary
image circles. (Other shape cuts will display their relative shape.)
The outer technicoloured circle indicates moissanite. (See Fig. 34)
Two inner circles of whitish light images are seen. The larger of
the white image circles is diamond (Fig. 33), the smaller white image circle
is CZ. Closely similar diameter circles occur for each identity regardless
of the stone diameter, provided the pavilion angles are similar.
It is all relative to the optical indices quoted in Table 1, and the Hodgkinson
Method.. Furthermore, other gem identifications or eliminations are
44: Pavilions Down
the three round stones are lying on their pavilions. They cast only
part of their outline, but it is ample. The pyrotechnics of moissanite
again stand out. Hundreds of diamonds can be screened for moissanite
in a minute or so.
45: Nelson Fingerprinter
This intriguing piece of equipment is ideal for laboratory
or appraisal use to provide a unique observation of important gems.
A photographic record can be made, not only of the pavilion facet plan,
but also the tiniest deviations and irregularities in facet placement which
show up. Photographs are easily taken, and would make a useful archival
record of a valuable gem. Such a record would also provide a "fingerprint"
in forensic work, as it would distinguish one diamond, ruby, emerald, etc.
from any other. The Nelson Fingerprinter is obtainable from Nelson
Gemmological Instruments, 1 Lyndhurst Road, London NW5 5PX.
Pour a diamond parcel into a clear plastic lid or box and cover with
water. Support the box above a white A4 paper, which acts as a screen
underneath. The box is best supported on a small glass shelf about
1" above the paper, so that light can pass down through the stones to the
paper. (The glass from a small, cheap photo frame about 10" x 8"
is ideal.) Position a fibre optic, or hold a pocket flashlight torch,
about 6" above the box. Simply move the clear box about laterally
on the glass shelf and below the light source. Improved performance
comes if you cover the light with a disc in which you cut a fine slit.
Best results are obtained in the dark. Trawl a pair of diamond tweezers
through the stones. Any moissanites will quickly reveal their presence
by their pyrotechnic movement, and can easily be picked out.
Some stones will lie table facet down, some pavilion down - it does
46: "Red Hot gold - Yellow Hot Moissanite"
Moissanite UK Ltd. were kind enough to provide specimens
of their faceted stones for research. During experiments at Hodgkinsons
Ltd., Glasgow, A colourless moissanite was placed in
molten gold and turned bright yellow, as seen in Fig. 35.
18ct gold melts at about 900oC, but Mark Kellam at C3 Inc. suggested
that, in the two minutes or more that the gold was kept at melting temperature,
the moissanite would absorb more heat and was possible reaching twice the
temperature of the gold. Still the stone survived.
At the C3 Inc. modern premises in Morrisville, North Carolina, Dr. Kellam
placed a diamond alongside a moissanite in a furnace fed with liquid oxygen.
At about 1050oC, I witnessed the diamond go intensely white hot before
it vaporised. The faceted moissanite survived intact.
The yellow colour transformation of synthetic moissanite under the effect
of heat is not thermoluminescence, but simply that the material is yellow
at raised temperature. Intriguingly, the cubic polytype form of silicon
carbide is yellow at room temperature, but this isotropic form has only
rarely been grown, as by Dr. Nelson in 1948.
On rare occasions a certain type of diamond thermofluoresces under the
heating effect of a jewellery workshop gas torch. In such a rare
instance the off-whitish appearance is far removed from moissanite's bright
yellow colour change response to heat. Such rare thermofluorescing
diamonds seem always to be associated with a strong 478nm absorption line.
anyone add confirmation to this, please?
47: What's Cooking?
the experiments with the molten gold, I wondered how moissanite's yellow
response to heat could be monitored, and at how low a temperature the material
would turn yellow. A mixture of diamonds and moissanites lie cold
on the hot plate of an electric oven. How many moissanites are there?
48: The oven hotplate
oven hotplate was turned up to a medium setting. Once hot, it was
only seconds before the two moissanites had turned bright yellow.
Such an experiment would allow hundreds of diamonds to be tested at one
Glass Filled Diamonds?
Glass fillings leak at such temperatures, so this procedure offers
a simple way to check out a diamond parcel. If sold honestly as "glass
filled", then check the diamond identity as described under the heading,
"Diamond Parcels". Figs 43, 44.
49: Diamond Scoop
greatest ease I placed a diamond scoop on the hotplate until it became
hot. Using a glove, I used the scoop to pick up five stones and return
them to the oven hot plate. In seconds you see the four moissanites
by their new yellow colour. Obviously the scoop could handle many
The shiny bright chromium plating of the scoop distracts the eye from
seeing the result clearly and I experimented with unpolished aluminium
foil on the scoop. The latter precaution, plus a white overhead light,
made the observation instantly positive, especially as the "whiteness"
of the diamond provided ample contrast.
50: And so to bed
ordinary bed light is used here with a 250 watt lamp bulb. Again
the stones turned yellow. This time at a temperature measured at
231oC. Lower wattage bulbs did not achieve the colour change.
Dr. Mark Kellam advises that the colour change temperature will have some
variation depending on the potential impurities that can be hosted by synthetic
51: More than match for diamond!
title begs the question. "Will it work?" Hold a match (or cigarette
lighter) flame tip just below the stone (mounted or loose). The syntheic
moissanite turns yellow in seconds. Any sootiness to the stone rinses
off in cold water.
52: Moissanite colours
beautiful sea green moissanite contrasts with a colourless 1.26ct
stone (M colour grade). In Carolina I was privileged to see a range
of beautiful colours, but the main preoccupation was to deliver the colourless
goods ordered from many countries around the world.
53: Bluish Synthetic Moissanite
A more subdued greyish blue synthetic moissanite is
reminiscent of certain natural diamond colours
Answer to the diamond identity question asked in Figure 1
Top left 1.24ct synthetic moissanite, 1.01ct diamond (F colour), 1.24ct
diamond (L colour), 1.45ct strontium titanate, 2.56ct cubic zirconia, 2.22ct
GGG, 1.30ct zircon, 1.78ct YAG, 1.11ct synthetic spinel . The stones are
arranged in descending refractive order. Because of quality and cutting
differences, the two diamonds appear to be two different optical identities.
I would not like to have to answer such a question with the nine stones
full frontal in this manner, but hand them to me in a dark room (loose
or set), and I will happily separate them one from the other, without seeing
them, without touching them, and without instruments. I have had a lot
of fun and pleasure sharing this identification technique with gemmologists
in various parts of the world, but then "Visual optics" is meant to be
fun, apart from its extraordinary contribution to the gem identification
Help and encouragement is appreciated from
Dr. J Nelson,
Doug Morgan, John and Catriona McInnes, Tom Bain, Gillian and the directors
of Alan Hodgkinson Ltd, David Wright family, David Pilling family, Richard
Cartier, Moissanite UK Ltd., Consultants: Dr. Kurt Nassau and Howard Rubin.
C3 Inc. President Bob Thomas, Chairman Jeff Hunter, Technical Research
Director Dr. Mark Kellam, and Earl Hines, designer and controller of moissanite
gem cutting and polishing.