June 2018
De Beers Consumer Confidence Technical Research
and Diamond Verification Instruments
(Synthetic Diamonds and their Detection)
Philip Martineau & Colin McGuinnessDe Beers Technologies, Belmont Road, Maidenhead, SL6 6JW, UK
2The De Beers Group of Companies
If we could succeed at a small expenditure of labour in converting carbon into diamonds, their value might fall below that of bricks.
(Karl Marx)(1818-1883)
synthetic^
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De BeersConsumer Confidence Programme
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• Proactive research to identify future detection challenges
• Development of understanding and technology necessary to remove detection challenges
• Provision of technology solutions for the trade: equipment sales and services
Consumer Confidence Technical Research Philosophy
Commercially Viable
Difficult to Detect
Technologically Possible
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D i a m o n d F o r m a t i o n
• Formed in the earth’s upper mantle at
temperatures of 900 - 1200°C
• Formed 0.9 - 3.5 billion years ago
• Brought up in Kimberlite / lamproite eruptions,
many during the Cretaceous period: 146 million -
65.5 million years ago)
• Stored at about 1000°C for hundreds of millions of
years at least 110 km below the earth’s surface
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M O R P H O L O G Y: N AT U R A L D I A M O N D S
• Natural diamonds show a predominantlyoctahedral morphology
– Octahedral faces dominate being the slowest growing faces
– Cube faces not observed
• Dissolution is responsible for the formation of{110} (dodecahedral) faces and ‘rounding’ ofsome natural diamonds
Octahedral Faces No cube Faces
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Schematic diagram: HPHT synthesis
Temperature-gradient method
Metalsolvent/catalystNickel/IronCobalt/Iron
◆ Temperature = 1300 – 1500oC
◆ Pressure = 50 – 60 kbar
ANVIL
ANVIL
Heater
Graphite powder
Metalsolvent/catalyst
Seed
T1
T2
T1 > T2
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M O R P H O L O G Y: H P H T S Y N T H E T I C D I A M O N D
• The relative growth rates of the various faces are different in HPHT synthetic diamond
• Both cube and octahedral faces remain (cubo-octahedral morphology)
• Chemical environment and growth temperature can also affect the shape
- Minor facets {113}, {115}
‘Type I’ material ‘Type II’ material
Octahedral faces Cube face still present
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Diamond Absorption Spectroscopy
CVDHPHT
natural
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
200 300 400 500 600 700 800
ab
so
rpti
on
co
eff
. (c
m-1
)
wavelength (nm)
uvvis model
[NC]
[NA]
[N3]
45 ppm10 ppm15 ppm
A centresSingle NN3
Type Ib
Type IaB
Type IaA
Type IaAB
Ab
sorb
ance
Wavenumber cm-1
Wavelength (nm)
Ab
sorp
tio
n c
oef
fici
ent
(cm
-1)
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HPHT synthesis v. natural: what differences can we expect?
• Synthetics have not remained at high temperature for hundreds of millions of years
• Less/different aggregation of nitrogen impurity
• The DiamondSure screening instrument makes use of this difference
• HPHT synthesis relative to natural growth
– Uses a different chemical environment and takes place at a higher temperature
• Metallic inclusions: visual inspection
• Different crystal shape: DiamondView
10
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{100} {111} {110} {113}
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DiamondView images of diamonds
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BACKGROUND - SYNTHESIS PROCESSES
Chemical Vapour Deposition (CVD)
Chemical Vapour Deposition
Schematic
to pump
gases in
observation
window
synthetic
substrates
microwaves
vacuum
window
PLASMA
GIA.com
SCIOdiamond.com
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DETECTION OF SYNTHETIC DIAMONDS
Growth & luminescence images - DiamondView
natural HPHT synthetic CVD synthetic
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Gems & GemologySpring 2004
Nitrogen-doped Heat treatedNitrogen-doped
Boron doped High purity
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CVD SYNTHETIC DIAMONDS – DISLOCATIONS FROM DEFECTIVE GROWTH
DiamondView images – effect of filtering
filtered (orange)unfiltered
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0
1000
2000
3000
4000
5000
6000
500 550 600 650 700 750 800 850
PL
in
ten
sit
y
wavelength (nm)
Gemesis CVD synthetics: PL(LHR) lex=514.5nm(Ar) T=77K
NL495-1
NL495-4
57
5
73
7
63
7
Ram
an
CVD SYNTHETIC DIAMONDS
Photoluminescence spectroscopy & DiamondPLus™
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MELEE SIZED DIAMONDS
Screening & Detection
Rough diamonds
As-grown HPHT synthetics ($15/ct)Polished melee should be screened beforesupply to brands and jewellery manufacturers
Jewellery and watchescontaining meleeDo the mounted stones needscreening as well?
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SYNTHETIC DIAMOND MELEE – De Beers Screening equipment (June 2014)
loose melee: AMS
mounted melee: DS Mount
AMS(Automated Melee Screening)360 stones/hourAbsorption and Raman/PLspectroscopy
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NEXT GENERATION SCREENING………..
Customer Wish List
• Automated feeding, measurement and dispensing
But,
• Faster
• Extend to smaller stones
• Must be able to test all shapes/cuts
• Minimise requirement for further testing (lowest possible referral rate)
• Specific detection of synthetics
“A synthetics screening machine that is as easy to use and as low cost as a digital weighing machine……and one in every office of the bourse”
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1
10
100
1000
10000
0 20 40 60 80 100 120
Co
un
ts
Time (milliseconds)
Decay profile of natural diamond phosphorescence @ 455 nm
Decay
Fit
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
250 300 350 400 450 500 550 600 650 700 750 800
Ph
osp
ho
resc
ence
(a.
u.)
Wavelength (nm)
Phosphorescence from natural diamond
Time-resolved photoluminescence spectroscopy of natural diamond
• Room temperature• Above band gap
excitation
Almost all natural diamonds show blue phosphorescence with a characteristic colour and decay time.No known synthetics show this combination of colour and decay characteristics.
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Illumination: Visible UV excitation UV excitation UV excitation UV excitation
Naturaldiamond
HPHTsynthetic
CVDsynthetic
Fluorescence Phos 1 Phos 2 Phos 3
Time-resolved imaging of UV-excited luminescence
Image captured duringUV excitation pulse
Image captured after90 µs delay
Image captured after3 ms delay
Image captured after70 ms delay
Increased delay after end of UV excitation pulsed
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AMS2• Allows screening of smaller stones:
– down to 0.3 pt (0.9 mm) for round brilliants
• All cuts/shapes (fancy cuts from 1 pt)
• Faster: up to 3600 stones/hour
• Simulants dispensed into non-diamond bin
• HPHT synthetics and CVD synthetics dispensed into synthetics bin
• No synthetics or simulants will be passed but some may be referred for further tests
• Fewer natural diamonds referred for further testing: < 0.25%
– non-automated testing of the measurement
principle on more than 6 million stones has given
overall referral rates significantly less than 0.25%
• Primarily for colourless and near-colourless melee
– but failsafe for stronger colours
Five bins• Non-diamond• Synthetic• Refer• Pass• Purge
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• Makes use of a characteristic of natural diamond not seen
in synthetics (fast decaying blue phosphorescence)
• Can be used to test loose or mounted stones
• Semi-automated decision: touch screen or click on image
• Referral for further testing is not based on type categories
• Non-automated testing on >6 million stones
• Referral rates less than 0.1%
• Primarily for colourless and near-colourless
melee but failsafe for stronger colours
SYNTHdetect
(Patent application: WO2017001835)
SYNTHdetect
AMS2
Technological development is driving down the cost of producing synthetics
Increasing discount for synthetic v. natural diamond in the trade
Increased incentive for dishonest behaviour
Technology is driving down the cost of detecting synthetics
Increasing risk for dishonest people
Sanctions applied to cheats will act as a deterrent
Technology for lower cost detection - an important enabler for maintaining trade confidence and consumer confidence
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With thanks to:
The De Beers Technologies CCTR team: David Fisher, Riz Khan, Brad Cann, Nick Davies, Colin McGuinness, Dave
Evans, Sam Sibley, Julia Samartseva, Matthew Dale, John Freeth, Hugh Leach, Cristina Martins
Element Six synthesis and treatments research team members over many years.
All members of De Beers Technologies Instrument Development teams: particularly Paul Spear, Simon Lawson,
Siobhan Dgama, Nick Davies, Peter Lanigan, Peter Rose, Andy Portsmouth
THANKS FOR YOUR ATTENTION
Acknowledgements
• Jewellery brand using laboratory-grown diamonds from Element Six
• Will launch in September 2018
• Colours available: colourless, pink and blue
• Fully disclosed – internally marked (0.25 – 1 ct)
• $800/ct + $100 (silver setting) or $200 (10 karat gold)
Diamond blockchain initiative to track diamond attributes & transactions along the value chain