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Diamond Identification
Dr.James
ShigleyGemologicalInstituteofAmerica
Carlsbad,California
GIAResearch
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PresentationOutline
Identification:NaturalColoredDiamonds
Synthetic
DiamondsClarityTreatedDiamondsColorTreatedDiamonds
Summary
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NaturalColored
Diamonds
22.28caratChameleon Diamond
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Diamond
CharacterizationGemology:
Internal
features
(inclusions,
color
distribution,
luminescence)Ultravioletfluorescence
Absorptionspectrapattern
Strain
pattern
and
intensityPhotomicrographsandfluorescenceimages
Spectroscopy:
Midinfraredabsorption
Ultravioletvisiblenearinfraredabsorption
Photoluminescence
Ramanidentificationofsignificantinclusions
1
1.5
2
2.5
4500 4000 3500 3000 2500 2000 1500 1000
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Diamond
Type
Classification
TypeI
TypeIaaggregatednitrogenatoms
(IaA,IaB,IaAB subcategories)
TypeIbdispersed
nitrogen
atoms
TypeII
TypeIIafew
if
any
impurities
TypeIIbdispersedboronatoms
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Absorption
Spectroscopy
.5
1
1.5
2
2.5
3
3.5
4000 3500 3000 2500 2000 1500 1000
-.05
0
.05
.1
.15
.2
.25
400 500 600 700 800 900
Infraredspectra
Visiblespectra
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Luminescence
Spectroscopy
0
50000
100000
150000
200000
550 600 650 700 750 800 850
Luminescencespectra
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Photography
Faceup
Externalfeatures Inclusions
Strain Fluorescence
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Data
Collection
for
each
Diamond
1.2
1.4
1.6
1.8
2
2.2
300 400 500 600 700 800
0
50000
100000
150000
200000
250000
500 600 700 800 900
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
10000 8000 6000 4000 2000
Weight/Cut: 1.00ct/cushion
Color: FANbr
PK
Clarity: SI2
LWUV: mediumBlue
SWUV: weakBlue
Spectra: nosharplines
Strain: weakcrosshatched
Inclusions:none
DiamondView
Crosspolarized20x
Infraredabsorption UVVisibleNIRabsorption
Photoluminescence
488 laser
514 laser
633 laser
830 laser
midIRnearIR
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Groups
of
Natural
Diamonds
TypeIa
Cape
TypeIb
TypeIIb
Orange
Pink
Chameleon
Green
DtoZcolors
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Diamond
Color
versus
Market
Value
Market
Value
Color
Colorless Faintcolor Fancycolor
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Colored
Diamond
Publications
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HPHT
Grown
Synthetic
Diamonds
As-Grown
TType Ib
Type IIb
Type Ib + IIb
Type IIa
Treated
Annealing
Irradiation
+
Annealing
Irradiation
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HPHTGrown
Synthetic
Diamonds
Diamondgrowthoveraperiodofseveraldaysathighpressuresandtemperatures(HPHT)fromametalsolvent
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HPHTGrown
Synthetic
Diamonds
Welbournetal.,Gems&Gemology,Fall1996
Cuboctahedral crystalmorphology
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HPHTGrown
Synthetic
Diamonds
Welbourn
et
al.,
Gems
&
Gemology,
Fall
1996
Internalarrangementofgrowthsectors
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HPHTGrown
Synthetic
Diamonds
Internalarrangementofgrowthsectors
Welbournet
al.,
Gems
&
Gemology,
Fall
1996
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HPHTGrown
Synthetic
Diamonds
Colorzoningpatterns
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HPHTGrown
Synthetic
Diamonds
Internalgrainingpatterns
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HPHTGrown
Synthetic
Diamonds
Inclusions
of
flux
metals
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HPHTGrown
Synthetic
Diamonds
Ultravioletfluorescencecolorsandpatterns
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Synthetic
Diamond
Chart
Gems&
Gemology
(Winter
2004)
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CVD
Grown
Synthetic
Diamonds
Diamondgrowthatlowpressuresandhightemperatures
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Asgrown
colorlessandnearcolorless
Asgrown
darkbrown
As
grownorange pink
HPHTtreated
colorlessandnearcolorless
HPHTtreatedyellow
Apollo
CVD
Synthetic
Diamonds
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Apollo
CVD
Synthetic
Diamonds
DTCDiamondView images
OrangyRed
UV
Fluorescence Blue
UV
Phosphorescence
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ApolloCVD
Synthetic
Diamonds
70x 40xSurfacecavitiesandfractures
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Apollo
CVD
Synthetic
Diamonds
Mosaicbirefringencepatternsseeninpolarizedlight
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ApolloCVD
Synthetic
Diamonds
100x 90xGirdlesurfaceandlaserinscriptionmarks
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Apollo
CVD
Synthetic
DiamondsVisibleAbsorption
0
5
10
15
20
300 400 500 600 700
Wavelength (nm)
Ab
sorptionCoefficient(cm-1)
620 640 660 680 700 720420 440 460 480 500
637
666 685 712495
503
413419
425
~520
~
270
637
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TypeIa (rarelyIIa) TypeIIaColorless(tolightyellow) Colorless(brown)Cape absorptionspectrum Nospectrumpattern
BlueUV
fluorescence Orange
UV
fluorescence
Weaktostrongfluorescence WeakfluorescenceComplexinternalgrowth BandedinternalgrowthOccasionalinclusions Inclusions rare
Octahedralor
irregular
shape Tabular
shape
TypeIa UVopaque TypeIIa UVtransparent
Natural CVDSynthetic
Colorless Diamonds
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Clarity
Enhanced
Diamonds
Alaserisusedtoburnanarrowopenchannelfromthesurfacetoa
mineralinclusion
Acidsareintroducedthroughthischanneltodissolveorbleachthe
inclusion
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Clarity
Enhanced
Diamonds
Morerecently,heatfromthelaserisusedtoextendapreexistingfracturetothe
surface,and
acids
are
introducedthroughthisfracturetodissolveor
bleachthemineral
inclusion
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Clarity
Enhanced
Diamonds
Patternsofinternallaserdamage
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Clarity
Enhanced
Diamonds
Opensurfacereachingfracturesarefilledwithahighrefractiveindexglasstohidetheirvisibility
Before After
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Clarity
Enhanced
DiamondsBefore After
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Clarity
Enhanced
Diamonds
Flasheffect colors
seen
with
magnificationagainstbrightordarkbackgrounds
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Clarity
Enhanced
Diamonds
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Structure
Defects
in
Diamonds
Anidealdiamondthatisfreeofatomiclevel
defectsis
colorless
Allnaturaldiamondscontainvariousdefects
(impurity
atoms,
missing
or
displaced
carbon
atoms)
Someofthesedefectscanselectivelyabsorbvisible
light,
and
can
impart
various
colors
in
diamond
0.95carat
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Radiationproduces
vacanciesthat
selectively
absorbredlightandintroducebluecoloration
Whenannealed,
avacancy
combineswithnitrogentoformvariousdefectswhich
impart
yellow
or
yellowgreencoloration
Diamonds
Treated
by
Radiation
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Irradiated
Colored
Diamonds
Electronradiationproducesathinlayerofcolorbeneathfacetsurfaces
Reflectionsofthisthinlayercanbeseenasadistinctive
colorpattern
near
the
culet
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Irradiated
Colored
Diamonds
Acolorconcentrationatthe
culetdue
to
exposure
to
electronradiation
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1.4
1.6
1.8
2
2.2
2.4
2.6
400 450 500 550 600 650 700 750
Wavelength (nm)
Abs
orbance
ND1
GR2
GR3
GR1
Irradiated
Colored
Diamonds
Visiblespectrum
withabsorption
featuresdue
toradiationexposure
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Spectroscopy
of
Diamond
Liquidnitrogencryogenicunit
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1
1.5
2
2.5
3
350 400 450 500 550 600 650 700
Wavelength (nm)
Absorbance
H3H4
N3
594
Irradiated+Heated Colored
Diamonds
Visiblespectrumwith
absorption
featuresduetoheating
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Irradiated
(+
Heated)
Diamonds
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HPHT
Treated
Diamonds
Annealingatveryhighpressuresandtemperaturesforashorttimetochangediamondcolor
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HPHTTreatedDiamonds
~2200C
Lightbrown(typeIIa) Nearcolorless(H)
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HPHT
Treated
Diamonds
Surfacedamageduetoheatingathightemperaturesandpressures
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HPHT
Treated
Diamonds
TreatmentofbothTypeIandTypeIIdiamonds
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HPHTTreatedDiamonds
Internal
graphitization
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HPHT
Annealing
ExperimentsBeforetreatment
Aftertreatment
HPHT A li f Di d
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HPHTAnnealingofDiamond
1
1.5
2
2.5
3
350 400 450 500 550 600 650 700
Wavelength (nm)
Absorbance
AfterHPHT
BeforeTreatment
H3
N3
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HPHTIdentificationChallenges
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Diamonds
Treated
by
Multi
Processes
Major effects of radiation with or
without annealing:
Introduce vacancies
Produce H3 and H4 defects
Produce N-V centers
Major effects of HPHT annealing:
Remove plastic deformation-
related brown color
Release H-compensated
boron
Produce defects like H2 and
H3
Generate isolated nitrogen
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Multi
Process
Treated
Diamonds
Graphitizationalongfractures Etchedareasonsurface
Bothfeaturesareevidenceofhightemperatureannealing
M l i P T d Di d
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Aconcentrationofpink orangecolorattheculetisevidencethatadiamondhasbeenirradiatedandannealed
Type IIa
MultiProcessTreatedDiamonds
Type Ia
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1.5
2
2.5
3
3.5
4
450 500 550 600 650 700
Wavelength (nm)
Absorbance
N3
425
H3
594
637
(N-V)-
575
(N-V)0
H4
VisibleSpectrum(TypeIa)Multi
Process
Treated
Diamonds
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0.01 to 1.57 ct
Serenity
Surface
Coated
Diamonds
S it S f C t d Di d
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Iridescentthincoloredcoatingsonfacetsurfaces
SerenitySurfaceCoatedDiamonds
Serenity Surface Coated Diamonds
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SerenitySurfaceCoatedDiamonds
Visualevidenceofasurfacecoating
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New
Publication
from
GIA
Republicationof
articles
andotherinformationontreateddiamondsand
their
identification
that
haveappearedinGems&Gemologyoverthepast50years
Diamond Research Summary
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DiamondResearch Summary
Bycharacterizing
the
propertiesofdiamonds,wearecreatingadatabaseof
information
that
can
be
used
todeveloppracticalmeansfortheiridentificationtosupportthejewelrytrade
20.17carats
Gem Identification Summary
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GemIdentification Summary
In
addition
to
standard
testing
equipment,
today
gem
identificationoftenrequirestheuseofmoreadvancedanalyticaltechniquesforchemicalanalysisandspectroscopy
Identificationcriteria
must
be
based
on
the
study
of
gems
of
knownorigin(natural,synthetic,treated)
Correctidentification
must
be
based
on
multiple
criteria,
and
notjustthepresenceorabsenceofonefeature
GIA Gem Research Conference
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GIAGemResearchConference
Town&CountryResortandConventionCenter
SanDiego,
California
www.grc2009.gia.edu
GIA Research
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GIAResearch