De Beers Consumer Confidence Technical Research and Diamond Verification Instruments · 2018. 8. 21. · Time (milliseconds) Decay profile of natural diamond phosphorescence @ 455

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^


De BeersConsumer Confidence Programme


• 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


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


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


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


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


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)


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


{100} {111} {110} {113}


DiamondView images of diamonds


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


DETECTION OF SYNTHETIC DIAMONDS

Growth & luminescence images - DiamondView

natural HPHT synthetic CVD synthetic


Gems & GemologySpring 2004

Nitrogen-doped Heat treatedNitrogen-doped

Boron doped High purity


CVD SYNTHETIC DIAMONDS – DISLOCATIONS FROM DEFECTIVE GROWTH

DiamondView images – effect of filtering

filtered (orange)unfiltered


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™


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?


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


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”


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.


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


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


• 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


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

Documents

De Beers Consumer Confidence Technical Research and Diamond Verification Instruments · 2018. 8. 21. · Time (milliseconds) Decay profile of natural diamond phosphorescence @ 455