1
Michael S. Krzemnicki Swiss Gemmological Institute SSEF Switzerland
Photos and figures © H.A. Hänni & M.S. Krzemnicki
Treatment of corundum characteristics, detection and declarationSGG Zentralkurs, Thun, 15. April 2013
2 © SSEF Swiss Gemmological Institute Every&gemstone&deposit&produces&stones&of&high&and&low&quality.& Usually&the&quality&distribution&has&the&shape&of&a&pyramid.&& Top&stones&are&rare,&stones&of&lower&quality&are&very&abundant.& The&exploitation&of&gems&is&expensive,®ardless&of&their&quality.& It&is&economically&and&important&to&be&able&to&enhance&stones&of&& the&lower&part&of&the&quality&pyramid&(also&for&the&miners!)& Once&a&treatment&is&developed&and&successfull,&it&often&is&also&applied&& on&stones&of&better&quality&to&make&them&even&better&looking.& Quality& Quantity& Treatment options for corundum... To&modify&transparency:&& F&Gilling&of&Gissures&with&colourless&substance&&(oil,&artiGicial&resin,&glass)& F&heating&to&dissolve&inclusions& To&modify&colour& F&Gilling&of&Gissures&with&coloured&substance&(oil,&artiGicial&resin,&glass)& F&heating&in&oxidising&or&reducing&conditions&(±&with&additives)& F&diffusion&of&„colouring“&elements&into&the&corundum&lattice& F&irradiation& To&enhance&stability& F&Gilling&of&Gissures/cavities&with&solidifyig&substances&& To&create&optical&effects&& F&heating&with&additives& © SSEF Swiss Gemmological Institute
3 Treatment options for corundum... Time+scale+ © SSEF Swiss Gemmological Institute Fissure&Gilling&and&dyeing& Heating&with&blowFpipe& Heating&with&electrical&furnace& Irradiation& Heating&combined&with&surface&diffusion& Beryllium&diffusion& LeadFglass&Gissure&Gilling& CobaltFglass&Gissure&Gilling& Heating&with&borax&to&induce&Gissure&„healing“& next&treatment&??& 1000& 1900& 2000& Foiling,&Painting& 0& future& ©&F.&Notari& ©&H.A.&Hänni& Treatment options for corundum... Acceptance&in&the&trade&and&stability& © SSEF Swiss Gemmological Institute Fissure&Gilling&with&oil&& (±&colourless)& heating& irradiation& surface&diffusion& Beryllium&diffusion& LeadFglass&& Gillings& CobaltFglass&& Gillings& Heating&with&borax&to& induce&Gissure&„healing“& Acceptance+low& high& Stability+ low& high& dyeing&
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Pailin
© SSEF Swiss Gemmological Institute Talking about treatments... Fissure filling with colourless oil: Oiled&Gissures&often&found&in&rubies&or&sapphires&polished&as&beads.&& SSEF&discloses&oil&in&corundum&only&if&the&amount&in&Gissures&is&moderate& to&signiGicant.& © SSEF Swiss Gemmological Institute A&Gissure Gilled with oil,& showing&a&characteristic dendritic pattern© H.A. Hänni, SSEF
5 Photos © H.A. Hänni, SSEF red&dye&in&a&colourless&sapphire&and& in&pinkish&grey&star&corundum.& On&SSEF&reports,&such&a&dyeing& treatment&is&fully&disclosed!& Dyeing/staining with coloured oil: © SSEF Swiss Gemmological Institute Irradiation of corundum: Irradiation&with&high&energy&electromagnetic&radiation& (intense&SWUV,&XFrays,&gammaFrays).& Colourless&or&pale&yellow&stones&become&intensly& brownish&yellow&(amber&colour)&due&to&an&induced& colour¢re.&The&colour¢re&is&however¬+stable+ and&the&colour&will&thus&fade&in&daylight&after&some&time.& Detection+is+dif;icult.+Usually+these+stones+ are+exposed+to+a+„+fading+test“+under+a+ strong+light+source+(beware+of+heating!).+ Some&natural&untreated&yellow& sapphires&also&show&unstable& colour!&
6 Heating of corundum Colour&in&corundum&is&due&to&the&presence&of&iron&(Fe2+,&Fe3+),&titanium,&magnesium& and&chromium.&Very&important&in&this&respect&are&the&soFcalled&“intervalence&charge& transfer&processes”&with&titanium&Ti4+/Fe2+&and&with&iron&itself&Fe2+/Fe3+ Fe2+/Ti4+ results&in&blue& Fe2+/Fe3+ results&in&yellow& Heating&of&corundum&mostly&is&affects&the&valency&of&iron&Fe2+&and&Fe3+&found&as& chemical&impurities&within&the&corundum&lattice.&Secondly&it&may&also&result&in&the& release&of&titanium&Ti4+&into&the&lattice&by&dissolving&rutile&(internal&diffusion)& Fe2+ oxidising&heating Fe3+& Fe3+ reducing&heating Fe2+ By&this,&many&(but¬&all)&colour&changes&due&to&heating&can&be&explained.& Heating of corundum © Swiss Gemmological Institute SSEF
Heating
Heating of corundum
difGicult&to&detect&withµscope&
Low&temperature&heating&(<1000&°C),&e.g.&Mong&Hsu&rubies&and&pink&sapphires& effect:&colour&shift,&blue&colour&component&is&reduced&
Heating&>&1000&°C,&e.g.&for&geuda&corundum,&rubies&from&Thailand effect:&colour&modiGication,&reducing&visibility&of&inclusions&&
Heating
Heating
Heating&with&high&refractive&glass&Glux,&e.g.&lead&glass& effect:&signiGicant&enhancement&of&transparency&and&colour&(and&stability)&
Heating&with&borax&Glux,&e.g.&rubies&from&Mong&Hsu&(Burma)& effect:&signiGicant&enhancement&of&transparency&and&colour&&
Heating&with&chromium&diffusion&(shallow)& effect:&creation&of&shallow&colour&zone&
Heating&with&beryllium&diffusion&(lattice,&bulk),&e.g.&corundum&from&Songea effect:&signiGicant&colour&modiGication&
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© Swiss Gemmological Institute SSEF
with flux
with diffusion
usually&with&characteristicµscopic&features&
Mozambique ruby untreated Heated with an additive (borax)
Heated and fissure filled with high refractive glass (lead glass)
© Swiss Gemmological
Institute
SSEF
8 Low Temperature heating (below 1000° C) By&the&heating&at&low&temperature&at&oxidising&conditions,&the&blue&colour&component& is&reduced,&thus&a&better&red&to&pink&colour&is&achieved!& Before heating After heating © Swiss Gemmological Institute SSEF © SSEF Swiss Gemmological Institute zircon&inclusion&in&& unheated&corundum& zircon&inclusion&in&& heated&corundum& Detection&of&lowFTemperature&heated&corundum& with&theµscope&is&very&difGicult&
9 heating heating Raman&spectra&of&zircon&inclusions& ©&M.S.&Krzemnicki,&SSEF& boehmite AlO(OH)& FTIR&at&different&Temp. from Frost et al. 2000 © Swiss Gemmological Institute SSEF Raman&spectra&or&FTIR&spectra&can&be&very&important& for&detection&of&lowFT&heating&of&corundum&!& © Swiss Gemmological Institute SSEF Heating of corundum above 1000° C At&higher&temperatures,&it&is&possible&to&signiGicantly&enhance&or&modify&the&colour&of& corundum.&Furthermore,&it&is&possible&to&reduce&visibility&of&inclusions.&
10 Surface features indicating a heat treatment High&temperature heating may produce&„burnmarks“&on&the surface (but&usually stones heated at&high&temperature are reFpolished)& © SSEF Swiss Gemmological Institute © H.A. Hänni, SSEF Atoll structures © SSEF Swiss Gemmological Institute Melting and explosion of inclusions results&in&characteristic discoid features,&the&soFcalled&„atollFstructures“.& © H.A. Hänni, SSEF
11 The dissolution of rutile needles © SSEF Swiss Gemmological Institute © H.A. Hänni, SSEF Photos © H.A. Hänni, SSEF Rutile+needles+may+partly+dissolve+and+leave+ dust+tracks+in+their+former+place. © SSEF Swiss Gemmological Institute © H.A. Hänni, SSEF Partly+dissolved+rutile+results+in+blue+dots+due+to+the+release+ of+titanium+into+the+corundum+lattice+(internal+diffusion)+
12 Heating with high refractive glass flux © Swiss Gemmological Institute SSEF In&the&last&few&years&large&quantities&of&rubies&heated&at&low+temperatures with&a& high&refractive&glass&Glux&(e.g.&containing&lead,&bismuth...)&have&entered&the&market.& Heated and fissure filled with high refractive glass (lead glass) Mozambique ruby untreated Rutile&needles&may&be&still&present&(sometimes&rubies&show&even&star&effect&!)& from Andilamena, Madagascar © H.A. Hänni, SSEF © Swiss Gemmological Institute SSEF Blue&and&orange&„Glashes“&& (interferences)&along&leadFglass& Gilled&Gissures.&Also&with&distinct& Glattened&air&bubbles&along&Gissures.&& At&these&low&temperatures,&no& „healing“&of&Gissures&occurs!& Detection+easy+with+the+microscope! © H.A. Hänni, SSEF
13 © Swiss Gemmological Institute SSEF SEM&BSEµgraph:& Fissures&Gilled&with&Pb glass&are&bright.& Pb$glass+;illed+ruby+is+easy+to+ detect+with+chemical+analysis,+ radiography+and+ X$ray+microtomography XFrayµtomography of&PbFglass&Gilled&ruby.& © Swiss Gemmological Institute SSEF Easy+to+detect+with+microscope+!+ Colourless&corundum&with&distinct&CoF blue&Gissure&Gillings&(and&distinct&Co& spectra&!)& New: Heating with Co-bearing flux Photos & spectra© T. Leelawatanasuk & O. Papawarin, GIT
14 Flux&residues&in&tentacleFlike&irregular&pattern&in&a&ruby&from&Thailand&(Siam)&heated& with&a&borax&Glux.& Heating with a Flux (Borax: Na-B-Hydroxide): Microscopic Evidences © SSEF Swiss Gemmological Institute Residues&of&Glux&(glass)&in&thin&Gilms,&curved&tubes&and&networks,&forming&& a&soFcalled&„neoFhealing &Gissure. Photos © H.A. Hänni, SSEF Attention:+ polycrystalline ;lux in+;lux$melt synthetic ruby+!+
15 Quantification of flux residues © Swiss Gemmological Institute SSEF minor moderate& signiGicant& See&also&LMHC&Infosheet&1:&www.lmhcFgemology.org Page 1 of 2 Corundum • with residues from the heating process present in healed fissures • with residues from the heating process present in filled cavities Members of the Laboratory Manual Harmonisation Committee (LMHC) have standardised the nomenclature that they use to describe heat treatment in corundum and the degree to which fissure “healing” has occurred, and the residues that remain within the healed fissures and cavities, following the heating of corundum. Healed fissures1: Any corundum that shows indications of having undergone heat treatment and a degree of healing along (previous) fractures see Figure 1 which also contain a residue(s) from the heating process, shall be described as « species » ‘(natural) 2 corundum’, « variety » ‘ruby or sapphire’ « further information » ‘indications of heating’ (to modify the colour and/or transparency of the stone), plus the appropriate residue quantification terminology alpha numeric and/or text description3 See table 1 and examples in figures 2, 3 and 4. Note 1: As an option, e.g., for “simplified reporting” situations, the quantification of residues in healed fissures may be replaced by the statement ‘residues in healed fissures’ Note 2: Wording in parenthesis is optional Note 3: This clause may include the presence of small filled cavities a b Figure 1: Flux assisted healing of a fracture during the heating process. A fracture that has been healed by the synthesis of Corundum or other materials during the heat treatment or crystal growth processes. (Hänni, H.A., 1998) (a) schematic (b) actual Table 1: Residue quantification terminology Condition → No indications of heating Indications of heating (no residue) Indications of heating with residues in fissures Report Alpha numeric → NTE TE TE1 TE2 TE3 TE4 TE5 Report Text → No indications of heating Indications of heating Minor residue in fissures Moderate residue in fissures Significant residue in fissures Condition → Indications of heating with residues in cavities Report Alpha numeric→ C1 C2 C3 Report Text→ Minor Moderate Significant Residue in cavities Residue in cavities Residue in cavities 1 (see Information Sheet #3 for "corundum with glass filled fissures" and subsequent "corundum with/and glass")2 Wording in parenthesis is optional.3 In the cases of TE1 and TE2 (minor) or TE3 and TE4 (moderate), when the text version is selected a reference to the specific alpha numeric shall be indicated either by combining the two or placing an « x » in the appropriate point of the comparative scale. Heating with surface diffusion (shallow) © Swiss Gemmological Institute SSEF A&colouring&element&(titanium&or&chromium)&from&an&external&source&is&entering&the& corundum&lattice&during&a&prolonged&heat&treatment&at&high&temperature.&The&result& is&a&very&shallow&intensly&coloured&zone&at&the&surface.&The&colour&is&easily&lost&after& repolishing Cr-diffusion treated Untreated (or heated) Detection+with+the+microscope+and+chemically Photo © H.A. Hänni, SSEF
16 Comparison of&a&diffusion treated sapphire&(left)&with&a&natural sapphire&(right)&in& immersion.&The&facet edges and the girdle of the diffusion treated stone show characteristic colour concentrations surface diffusion natural © SSEF Swiss Gemmological Institute © H.A. Hänni, SSEF © R. Hughes Heating with beryllium diffusion (lattice, bulk) © Swiss Gemmological Institute SSEF Beryllium diffusion treated rubies from Songea (Tanzania) Beryllium&from&an&external&source&is&deeply&penetrating&the&corundum&lattice& during&a&prolonged&heat&treatment&at&high&temperature.&The&result&is&usually&a& signiGicant&colour&modiGication.& This&treatment&isµscopically&very&difGicult&to&detect,&as&an&eventual&orange&rim& is&often&very&difGicult&to&see.&The&colour&is&usually&stable&even&after&a&repolish&!& Photos © H.A. Hänni, SSEF
17 Detection of heating with beryllium diffusion © Swiss Gemmological Institute SSEF Difficult with the microscope! Photos © H.A. Hänni, SSEF Detection of heating with beryllium diffusion © Swiss Gemmological Institute SSEF Safe detection only with LIBS, LA-ICP-MS and SIMS LIBS&spectra of beryllium diffusion treated&orange&sapphire.& The&high&beryllium peak is measured&in&the glassy residue at the surface!& The&corundum shows smaller peaks,&indicating approx.&30&ppm&Be&(low traces!),&but& which is already enough for&a&colour modiGication.& Be Al Al Al
18 Multi-step Treatments: Creating a star effect © SSEF Swiss Gemmological Institute Beryllium&diffusion treatment followed by titanium diffusion treatment and&subsequent&annealing results&in&a&precipitation of tiny oriented rutile needles creating&a&surfaceFrelated star effect&(asterism).& Disclosure © Swiss Gemmological Institute SSEF The&Swiss&Gemmological&Institute&SSEF&uses&a&full&disclosure&policy&following&CIBJO and&LMHC&(Laboratory&Manual&Harmonization&Committee&with&the&members& CISGEM,&GAAJ,&GIA,&Gübelin&GGL,&GIT,&SSEF)&recommendations:& Unheated&ruby: F&No&indications&of&heating& Heated&ruby: F&Indications&of&heating& Heated&with&Glux: F&Lead&glass&Gilled&Gissures&and&cavities& &&&Extent:&signiGicant&(minor,&moderate)& &&&The&introduction&of&lead&glass&into&Gissures&involves&heating& &&&This&treatment&usually&applies&on&low&quality&stones.& F&Indications&of&heating&with&minor/moderate/signiGicant&& &&&residues&in&healed&Gissures& Heating&with&diffusion:&F&Indications&of&heating& &&&Colour&modiGied&by&shallow/lattice&diffusion&of&titanium/& &&&chromium/&beryllium&from&an&external&source& Internationally&harmonized&wording&for&the&conGidence&of&the&customers&!&
