GAHK Seminar March 2017| Page 0

Pigeon blood red & Royal blue:

Working towards an international standard

PDDr.MichaelS.Krzemnicki,SwissGemmologicalIns:tuteSSEFwww.ssef.ch

Photo©M.S.KrzemnickiandSSEF,exceptwhereindicatedotherwise

GAHK Seminar March 2017 | Page 1

Contents

1)Background

2)Workingtowardsaninterna:onalstandard:

TheharmonisedcriteriaofSSEFandGGL

3)Levelsofcriteria?

4)Crea:onofaninternalstandard

5)PigeonbloodredandRoyalblue:

Detailedexplana:onoftheSSEFcriteriawithspecialfocusonPigeonbloodred

6)Conclusions

7)Outlook

GAHK Seminar March 2017 | Page 2

Background

Thecolourofcorundumismainlyrelatedtothe

presenceofcolouringelements(andoccasionally

so-calledcolourcentres)initscrystalstructure.

Thecolourweseeisresul:ngfromtheinterac:on

ofelectronsofthesecolouringelements(and

colourcentres)withlightphotons(energy)when

exposedtoalightsource.Corundum:thebeautyofcolours

Colour=selec:veabsorp:on±emission(fluorescence)

GAHK Seminar March 2017 | Page 3

Background

-  Pigeonbloodredandroyalbluearetradecolourterms

-  notscien:fically(colorimetric)definedterms

-  sofarnointerna/onalstandard

-  strongdemandbythetradeforanindependentassessmentofcolourandtomen:oncolour

termsonlaboratoryreports

-  newtermsemerge(royalred,dragonred,Mekongwhiskyyellow,etc...)

-  historicallyperceivedasveryrareandexcep/onalinquality

-  impactonvalue

Photo©Chris7e‘s

GAHK Seminar March 2017 | Page 4

Background

References:

Theruby...wasgenerallyofcarmine,cochineal,orrose-

redcolour,withaplayofviolet;butthemostvaluable

wasthecolourofpigeon‘sblood.

Tradi:onally,theBurmesehavereferredtothefinesthueofrubyas"pigeon'sblood"(ko-twe),a

termwhichmaybeofChineseorAraborigin.

...Itmustbestressedthatthetruepigeon‘s-bloodredisextremelyrare,moreacolourofmindthan

thematerialworld.

"...askingtoseethepigeon'sbloodislikeaskingtoseethefaceofGod.“

Somehavecomparedthiscolortothecenterofalivepigeon'seye(Brown&Day,1955).

…thecolormostcovetedtodayisthatakintoaredtrafficsignalorstoplight.Itisaglowingredcolor,

duetothestrongredfluorescenceofBurmeserubies...

…TheBurmesematerialischrome-rich,whichgivesrisetostrong

fluorescencetoultravioletradia:onandacharacteris:c

absorp:onspectrum,aswellastothe„pigeon‘sblood“colour

associatedwithBurmesestones. Excerptfrompage217:

Keller(1983),Gems&Gemology,Vol.19,No.4,209-219.

Excerptsfrompages329-330:

Hughes(1997),Ruby&Sapphire.511pages.

1888

Excerptfrompage273:

Gordon(1888).OntheRubyMinesnearMogok,Burma

1983

1997

GAHK Seminar March 2017 | Page 5

Workingtowardsaninterna/onalstandard

TheharmonisedcriteriaofSSEFandGGL:

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Press release:

Switzerland’s SSEF and Gübelin Gem Lab agree

to harmonise ‘pigeon blood red’ and ‘royal blue’ standards

The Swiss-based Gübelin Gem Lab and Swiss Gemmological Institute SSEF,

recognised as the leading laboratories for coloured stone testing, have agreed to

harmonise their standards for the colour terms “pigeon blood red” and “royal blue.”

Their goal is to standardise the usage of these terms for the benefit of the international

gemstone trade.

The colour terms “pigeon blood red“ and “royal blue“ have been used for centuries by

the trade to describe, respectively, only the finest quality rubies and sapphires, which

aside from their distinct colours, invariably are stones of superior quality, and hence are

among the most coveted gems.

SSEFandGübelinGemlabusetheterms

pigeonbloodredandroyalblueonlyforrubiesandsapphires:

-  whichexhibitstrongredorbluecoloursatura:on

-  whichareuntreated

-  whichmeetspecificchemicalandspectroscopiccharacteris:cs

-  offinequalityintermsofinclusions,transparency,andcolourhomogeneity

Butfinallytheyarecolourtermsandthusassessedusingmastersetsofrubiesand

sapphiresaccordingtoaninternallaboratoryprotocol.

JointPressreleaseofSSEF&GGL1.Nov2015

Seewww.ssef.ch,Pressreleases

GAHK Seminar March 2017 | Page 6

Levels of criteria ?

-  shouldthesetermsjustbeusedasgeneric

colourterms?

-  orshouldtherebeaddi:onalcriteria(levels)

toqualifyforthesetwocolourterms?

Pagoda

Wikipedia:Apagodaisa7eredtowerwith

mul7pleeaves,builtintradi7onsorigina7ngas

stupainhistoricSouthAsia.

Mainques/on:“Pagoda-principle”yesorno?

GAHK Seminar March 2017 | Page 7

Levels of criteria ?

Ifweaccept,thatfurtherajributesarerequired,thentheonlyques:oniswheretosetthelimits.

-  forimita/onsorothergems?

-  forsynthe/crubyorsapphire?

-  fortreatedrubiesandsapphires?

-  linkedtoqualityrequirements(transparency,colourhomogeneityetc.)?

-  linkedtochemical/spectralspecifica:ons(influencingcolour)?

Flowchartoftreatmentop7onsforruby.©M.S.Krzemnicki

Shouldthesecolourtermsbeapplicable:

GAHK Seminar March 2017 | Page 8

Creation of an internal standard

Laboratorieshavetocreateinternalstandardstobeabletocorrectlyandconsistently

describegemmaterialsontheirlabreports.

Suchaninternalstandardmaybecomeinterna:onallyaccepted/harmonised(e.g.CIBJO,

LMHC,SSEF-GübelinGGL...).

RedspinelonSSEFGemstoneReport

Example:Fancycoloureddiamonds

GIAhasdefactocreateda„standard”terminologywhichtodayisgloballyacceptedinthe

trade.

GAHK Seminar March 2017 | Page 9

Creation of an internal standard

Examples:

-  Ruby/pinksapphire

-  Padparadscha

-  Paraibatourmaline/lightbluetourmaline(withCutraces)

-  Emerald/greenberyl(withCrtraces)

-  Colourchangeorjustslightcolourshipunderdifferentlightsources

-  Pearlcolours

Padparadschayesorno?

GAHK Seminar March 2017 | Page 10

Creation of an internal standard

Paraibatourmaline lightbluetourmaline(withCutraces)

GAHK Seminar March 2017 | Page 11

Creation of an internal standard

Thecolourgradingofrubyandsapphireismuchmore

complexthanfordiamonds.

Takingtheexampleofthetermpigeonbloodred,thenext

slidesshowourcriteriawhicharerequiredtoqualifyforthis

term.

Ourcriteriaforroyalblueareverysimilartotheonesof

pigeonbloodred,onlydifferinginthespectroscopic

(chemical)specifica:on.

Colourexamplesofpinksapphiretoruby

GAHK Seminar March 2017 | Page 12

Pigeon blood red

Harmonised criteria (SSEF & GGL):

Thefundamentalcriterioniscolour:

Thecolourofarubyisgradedbycomparisonwithamastersetof(natural)rubies.

Themainparametershue,satura:onandbrightnessareobserved.

Onlyrubieswithastrongsatura:onanda“vivid”redcolour(similartoredtrafficlight)withno

oronlyslightpurplishcolour:ntareaccepted.

RubymastersetforpigeonbloodredofSSEF

Pigeonbloodred notPigeonbloodrednotPigeonbloodred

GAHK Seminar March 2017 | Page 13

Pigeon blood red

criteria:

Colourobserva/on:

Basedonthreefactors:

1)  Lightsource(emissioncharacteris:cs)

2)  Observer(protocolandtraining)

3)  Observeditem(e.g.rubyorsapphire)

Togradecolourconsistently,thefirsttwofactorshavetobedefinedandstandardisedasmuchas

possible.

CIEChroma7citydiagram

Munsellcolourspaceandcharts

GAHK Seminar March 2017 | Page 14

Pigeon blood red

criteria:

Effectoflighttemperatureoncolourappearance:

TworubiesshowingweakandstrongLWUVreac:onunderdifferentlightsources.

Spectraldistribu7onofD50illuminant,

comparedtohalogenandfluorescentlight.

LWUV D65(6500K)daylight A(2800K)incandescentlight

GAHK Seminar March 2017 | Page 15

Pigeon blood red

criteria:

Standardizedcolourobserva/on:

-  Colourobserva:onfromthetop

-  Rubyslightly:lted20°inalldirec:ons

-  Standardisedlight(ideallycon:nuum,e.g.

filteredhalogenlampequivalenttoCIED50

illuminant,99+colourrenderingefficiency).

-  Therubyandthemasterstonesareplaced

directlybelowthelightsourceatapprox.20cm

distance.Lightintensityatthatpointapprox.

2200lux(sameasfordiamondsPAS1048.2,

§5.3.8,page5).

Spectraldistribu7onofD50illuminant,

comparedtohalogenandfluorescentlight.

ComparisonofD65(diamond)andD50

GAHK Seminar March 2017 | Page 16

Pigeon blood red

criteria:

Fluorescence:

Thebodycolourofpigeonbloodredrubiesiscomplementedbyastrongfluorescencewhen

exposedtoultravioletlight(LWUV:strong,SWUV:medium–mediumweak).

GAHK Seminar March 2017 | Page 17

Pigeon blood red

criteria:

Fluorescence:

Thefluorescenceiscausedbyhigh

chromiumcontentcombinedwith

lowironcontent.Itresultsina

dis:nct"innerglow"whenexposed

tosunlight(whichcontainsUV),an

effectwhichhasbeencovetedinthe

tradehistorically.

Innerglow

strongUVreac7on

Noinnerglow

weakUVreac7on

Rubieswithveryhighchromiumcontentandlowironconcentra:onhowevershow

reducedfluorescenceanddonotqualify.

GAHK Seminar March 2017 | Page 18

Pigeon blood red

criteria:

Chemicalcomposi/on:

Generallyonlyrubieswithverylowamountofiron(comparedtochromium)showfluorescence

intensitywhichmeetsourcriterionforpigeonbloodred.

Thechemicalcriterioncommonlyismetforrubieswhichformedinmarbledeposits,suchasin

Myanmar,Vietnam,Tajikistan,Afghanistan,Tanzania(e.g.Morogoro),Kenya,etc.

0.000

0.200

0.400

0.600

0.800

1.000

1.200

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800 0.900

Ironconcentra*on(wt%

Fe2O3)

Chromiumconcentra*on(wt%Cr2O3)

Afghanistan Burma EastAfrica Madagascar Mozambique Siam Tajikistan Vietnam Winza,Tanzania

0.000

0.200

0.400

0.600

0.800

1.000

1.200

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800 0.900

Ironconcentra*on(wt%

Fe2O3)

Chromiumconcentra*on(wt%Cr2O3)

Afghanistan Burma EastAfrica Madagascar Mozambique Siam Tajikistan Vietnam Winza,Tanzania

Cr2O3=Fe2O3

pigeonbloodredbasedonourcriteria

GAHK Seminar March 2017 | Page 19

Royal blue

criteria:

Thefundamentalcriterioniscolour:

Thecolourofasapphireisgradedbycomparisonwithamastersetof(natural)sapphires.

Themainparametershue,satura:onandbrightnessareobserved.

Onlysapphireswithastrongsatura:onanda“vivid”bluecolourbutnoaddi:onalcolour:nt

(greenish,greyishorpurple)areaccepted.

SapphiremastersetforroyalblueofSSEF.

Royalblue notRoyalbluenotRoyalblue

GAHK Seminar March 2017 | Page 20

Royal blue

criteria:

Spectralcriterionfor“Royalblue”:

-  Blueofstrongsatura:on,eitherpureorwithaveryslightpurplish:nt.

-  historicallycoinedforthebestqualityofsapphiresorigina:ngfromtheMogokareainBurma,itis

alsoappliedbySSEF&GGLforsapphiresfromothermetamorphicdeposits,suchasinMadagascar,

SriLanka,andKashmir.

-  UV-Visabsorp:onspectrumdominatedbyFe2+-Ti4+Intervalencechargetransfer.

AvaSoft 7.4 Sapphire, Sri Lanka

Wavelength [nm]750700650600550500450400350300

Abso

rbance

[A

.U]

1

0

© Swiss Gemmological Institute SSEF

MetamorphicsapphireAvaSoft 7.4 Sapphire Basaltic deposit

Wavelength [nm]700650600550500450400350

Ab

sorb

an

ce [

A.U

]

1

0

© Swiss Gemmological Institute SSEF

Fe2+-Fe3+IVCT

Fe2+-Ti4+IVCTFe3+

Absorbance

Absorbance

Basal/csapphire

basal7c metamorphic

GAHK Seminar March 2017 | Page 21

Pigeon blood red

criteria:

Treatment:

Onlyrubieswhichshownoindica:onsofany

treatment.

Basedonthehistoricalconnota:onofrarity

andexcep:onalquality.

Photo©Dreams7me.comPhoto©Twobadcats,www.etsy.com

Glassyresidues(borax)inhealedfissureofheatedruby

fromSiam.

GAHK Seminar March 2017 | Page 22

Pigeon blood red

criteria:

Pleochroism:

Differenttodiamond,ruby(andsapphire)is

op:callyanisotropicandshowsadis:nctpleochroism.

ruby: o-ray purplishred

e-ray slightlyorangered

Lamellartwinningrevealingthepleochroic

coloursofruby.Photo©H.A.Hänni

GAHK Seminar March 2017 | Page 23

Pigeon blood red

criteria:

Pleochroism:

Theperceivedcolourofarubyisaninterplayofits

pleochroiccolours.

Itisdependentfromtheorienta:oninwhichthe

gemstonehasbeencutfromtheroughcrystalandthe

orienta:onitislookedat.

©R.Scoh,Jewelery-Secrets.com

SSEF&GGL:

-  Colourobserva:onfromthetop

-  Rubyslightly:lted20°inalldirec:ons

GAHK Seminar March 2017 | Page 24

Pigeon blood red

criteria:

Propor/ons:

Verydifferenttodiamonds,rubies(andsapphires)arerarelycutin“ideal”propor:onswhich

wouldmaximizetheyieldofinternallyreflectedlight(whenviewedthroughthetable).

Theircutisratherreflec:ngtheshapeoftheroughandweightconsidera:ons,openresul:nga

transmission“window”,whichmay–incombina:onwithpleochroism–stronglycontributeto

thevisualappearanceofthestone.

min. ~ 30 %

GAHK Seminar March 2017 | Page 25

Pigeon blood red

criteria:

Zoning:

Rubies(andsapphires)openshowcolourzoning,

i.e.varia:onsincoloursatura:on.

Ifcutproperly,theeffectofsuchzoningmightbe

minimisedwhenviewedfromthetop.

Pigeonbloodredonlyforrubieswithnoto

insignificantzoningwhenviewedfromthetop.

Twoexamplesofrubieswithstrongcolour

zoningnotfiingforpigeonbloodred.

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Pigeon blood red

criteria:

Colourmodifier:

Rubiesopencontainfissuresorcavi:esfilled

withorangesubstancesuchasironhydroxide

orevenorangeoil.

Althoughonlylocallypresent,suchcolour

modifiermayshipthecolourofastone

considerably.

Pigeonbloodredtermnotapplicableforsuch

stones.

Orangefissurefillinginarubyshijingits

originallypurplishredbodycolourintored.

GAHK Seminar March 2017 | Page 27

Pigeon blood red

criteria:

Orangefissurefillinginarubyshijingits

originallypurplishredcolourintored.

Colourmodifier:

Similarsitua:onalsoincaseofthispinksapphire

whichdoesnotqualifyforpadparadscha.

GAHK Seminar March 2017 | Page 28

Pigeon blood red

criteria:

Thesecolourlessinclusionsandtheweak“silk”in

zonesdonotaffecttheperceivedcolourofthisruby.

Inclusions:

Theymustberela:velyfreeofeye-visible

ordarkinclusionswhenviewedfromthe

topwithapprox.20cmdistancetothe

ruby.

Inclusionsandweaktomedium“silk”in

zoneswhichdonot(oronlyslightly)

affectperceivedcolourareacceptable.

GAHK Seminar March 2017 | Page 29

Pigeon blood red

criteria:

Transparency:

Rubymustshowvividinternalreflec:ons.

TheStarofKashmir(approx.20ct)

„sleepy“ „vivid“internalreflec:ons

GAHK Seminar March 2017 | Page 30

Conclusions

-  Thetradetermspigeonbloodredandroyalbluehistoricallyarenotusedaspurecolour

termsbutlinkedtorarityandexcep/onalquality.Thisconnota:onmakesthesetermsso

valuableforthetradeandconsumers.

-  SSEFandGübelinGGLhaveharmonisedtheircriteriain2015.Butresultsmays:lldiffer,as

colourgradingisfinallyanindependentopinionofeachlaboratory(similartodiamond

grading).

-  Colourgradingisfollowingainternallystandardisedprotocol.

-  Onlyforrubies/sapphiresfizngallcriteria

-  Onlyarestrictednumberofrubies/sapphiresareajributedthecolourgrades“pigeonblood

red”or“royalblue”basedonthepresentedstrictcriteria.

GAHK Seminar March 2017 | Page 31

Conclusions

Summaryofourcriteria:

-  Astrongredorbluecolour(comparedtomasterstones)

-  Onlyforrubiesandsapphiresformedinnature

-  Onlyforuntreatedrubiesandsapphires

-  Specificchemicalandspectroscopicproper:esrelatedtocolourappearance

(e.g.fluorescenceinrubies,par:altransmissionintheredforsapphires)

-  Notrestrictedtoasinglesource,butrathertoageologicalsezng

-  Homogeneityofcolour(orienta:onofcut,pleochroism)

-  Goodpropor:ons,avoidingdominant“windowsitua:on”

-  Noapparentcolourzoning

-  Nocolourmodifierbyfissurefillings

-  Noapparentanddisturbinginclusions

-  Goodtransparency,dis:nctinternalreflec:ons

-  Colourgradingisfollowingainternallystandardisedprotocol.

-  Weusea5000KD50daylightequivalentillumina:on(con:nuum)

-  Minimum“4-Eyes”principle

GAHK Seminar March 2017 | Page 32

Workingtowardsaninterna/onalstandard

Outlook:

Directlinkfordownload:

www.ssef.ch/fileadmin/Documents/PDF/650_Presenta/ons/2016_CIBJO_colourterms_SSEF.pdf

Openaccesstocriteria

Downloadaslightlymodifiedversionof

thispresenta:ononourSSEFwebsite.

www.ssef.ch

GAHK Seminar March 2017 | Page 33

Workingtowardsaninterna/onalstandard

Outlook:

CIBJOWorldJewelleryFedera:on:

Invitedspeakerandpresenta:onofcriteriaata

SpecialSessionoftheCIBJOCongressinYerewan

(Armenia),October2016.

GAHK Seminar March 2017 | Page 34

Workingtowardsaninterna/onalstandard

Outlook:

-  Weareconvincedthatstandardisingandharmonisingtheuseofthesecolourtermsis

importantforthetradeandlaboratories.

-  TheSSEF&GübelinGGLharmonisa:onofcriteriamaybeconsideredafirststepinthis

direc:on.

-  Anyorganisa:on/laboratorywhichwouldliketojointhisharmonisa:oniswelcome.

-  Wearereadytoduplicateourrubyandsapphiremastersetsfororganisa:ons,laboratoriesand

trademembers.

GAHK Seminar March 2017| Page 35

Thank you for your attention!

Highlyajrac:vepinkishredcolour!

The„QueenofBurma“(23ct)

soldforUS$6mioatChris:e‘sGeneva,2014.