GAHK Seminar March 2017| Page 0 Pigeon blood red & Royal blue: Working towards an international standard PD Dr. Michael S. Krzemnicki, Swiss Gemmological Ins:tute SSEF www.ssef.ch Photo © M.S. Krzemnicki and SSEF, except where indicated otherwise
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
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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.
GAHK Seminar March 2017 | Page 26
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.