SGG Corundum Treatment.Pptx

The beauty of colour

SGG Zentralkurs, Thun, 15. April 2013

Treatment of corundum

characteristics, detection and declaration

Michael S. Krzemnicki

Swiss Gemmological Institute SSEF Switzerland

Photos and figures © H.A. Hänni & M.S. Krzemnicki

1! Consumer+expectation+ Quality& 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.&

Gem$deposit+production+ 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& &

2! Treatment options for corundum...

Fissure&Gilling&and&dyeing& & Foiling,&Painting&

Heating&with&blowFpipe& ©&F.&Notari& Heating&with&electrical&furnace& ©&H.A.&Hänni& Irradiation& Heating&combined&with&surface&diffusion& Heating&with&borax&to&induce&Gissure&„healing“& Beryllium&diffusion& LeadFglass&Gissure&Gilling& & CobaltFglass&Gissure&Gilling& & next&treatment&??& & future& 0& 1000& 1900& 2000& Time+scale+ & © SSEF Swiss Gemmological Institute!

Treatment options for corundum...

Acceptance&in&the&trade&and&stability&

& heating& Heating&with&borax&to& high& induce&Gissure&„healing“&

Beryllium&diffusion&

CobaltFglass&& Stability+ + Gillings& LeadFglass&& Fissure&Gilling&with&oil&& Gillings& (±&colourless)& irradiation& surface&diffusion&

low& & dyeing&

low& Acceptance+ high& & + & © SSEF Swiss Gemmological Institute!

3! Talking about treatments...

Pailin!

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.&

A&Gissure&Gilled&with&oil,& showing&a&characteristic&

4! Dyeing/staining with coloured oil: red&dye&in&a&colourless&sapphire&and& in&pinkish&grey&star&corundum.& & On&SSEF&reports,&such&a&dyeing& treatment&is&fully&disclosed!&

Photos © H.A. Hänni, SSEF

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.&

Some&natural&untreated&yellow& sapphires&also&show&unstable& colour!&&

Photos © H.A. Hänni, SSEF

Detection+is+dif;icult.+Usually+these+stones+ are+exposed+to+a+„+fading+test“+under+a+ strong+light+source+(beware+of+heating!).+

5! Heating of corundum

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.&

6! 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&& Heating &effect:&colour&modiGication,&reducing&visibility&of&inclusions&& & usually&with&characteristicµscopic&features& & & Heating&with&high&refractive&glass&Glux,&e.g.&lead&glass& &effect:&signiGicant&enhancement&of&transparency&and&colour&(and&stability)& & Heating

with flux flux with 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& Heating &effect:&signiGicant&colour&modiGication& with diffusion diffusion with

Mozambique ruby Heated Heated and fissure filled untreated with an additive (borax) with high refractive glass (lead glass)

7! Low Temperature heating (below 1000° C)!

Before heating

After heating

By&the&heating&at&low&temperature&at&oxidising&conditions,&the&blue&colour&component& is&reduced,&thus&a&better&red&to&pink&colour&is&achieved!&

Detection&of&lowFTemperature&heated&corundum& with&theµscope&is&very&difGicult&

zircon&inclusion&in&& zircon&inclusion&in&& unheated&corundum& heated&corundum&

8! Raman&spectra&or&FTIR&spectra&can&be&very&important& for&detection&of&lowFT&heating&of&corundum&!&

& heating boehmite&AlO(OH)& FTIR&at&different&Temp.&

from Frost et al. 2000

Raman&spectra&of&zircon&inclusions& ©&M.S.&Krzemnicki,&SSEF& heating

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.&

9! Surface features indicating a heat treatment

! High&temperature&heating&may&produce&„burnmarks“&on&the&surface& ! (but&usually&stones&heated&at&high&temperature&are&reFpolished)& © H.A. Hänni, SSEF

Atoll structures Melting&and&explosion&of&inclusions&results&in&characteristic& discoid&features,&the&soFcalled&„atollFstructures“.&

10! The dissolution of rutile needles

Rutile+needles+may+partly+dissolve+and+leave+ dust+tracks+in+their+former+place.!

Photos © H.A. Hänni, SSEF © SSEF Swiss Gemmological Institute!

Partly+dissolved+rutile+results+in+blue+dots+due+to+the+release+ of+titanium+into+the+corundum+lattice+(internal+diffusion)+

11! Heating with high refractive glass flux

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 Mozambique ruby with high refractive glass untreated (lead glass) from Andilamena, Madagascar Rutile&needles&may&be&still&present&(sometimes&rubies&show&even&star&effect&!)&

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!+

12! SEM&BSEµgraph:& Fissures&Gilled&with&PbF glass&are&bright.&

Pb$glass+;illed+ruby+is+easy+to+ detect+with+chemical+analysis,+ XFrayµtomography& radiography+and+ of&PbFglass&Gilled&ruby.& X$ray+microtomography+

New: Heating with Co-bearing flux

Photos & spectra© T. Leelawatanasuk & O. Papawarin, GIT!

Colourless&corundum&with&distinct&CoF blue&Gissure&Gillings&(and&distinct&Co& spectra&!)& Easy+to+detect+with+microscope+!+

13! Heating with a Flux (Borax: Na-B-Hydroxide): Microscopic Evidences

Flux&residues&in&tentacleFlike&irregular&pattern&in&a&ruby&from&Thailand&(Siam)&heated& with&a&borax&Glux.&

Photos © H.A. Hänni, SSEF

Attention:+ polycrystalline+;lux+ in+;lux$melt+ synthetic+ruby+!+

Residues&of&Glux&(glass)&in&thin&Gilms,&curved&tubes&and&networks,&forming&& a&soFcalled&„neoFhealing&Gissure.&

14! Version 4. December 2011

Information Sheet #1 Standardised Gemmological Report Wording (To be approved by 15 January 2012)

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.

Quantification of flux residues

a b

Figure 1: Flux assisted healing of a fracture during the heating process. A fracture that has been healed by the synthesis of Corundumminor or other &materials during the heat treatment moderate&or crystal growth processes. (Hänni, H.A., 1998) (a)signiGicant& schematic (b) actual

Table 1: Residue quantification terminology Condition → No indications Indications of Indications of heating with residues in fissures of heating heating (no residue) Report Alpha NTE TE TE1 TE2 TE3 TE4 TE5 numeric → Report Text No indications Indications of Minor residue in fissures Moderate residue in Significant residue → of heating heating fissures in fissures Condition → Indications of heating with residues in cavities Report Alpha C1 C2 C3 numeric→ Report Minor Moderate Significant Text→ Residue in cavities Residue in cavities Residue in cavities

See&also&LMHC&Infosheet&1:& www.lmhcFgemology.org& 1 (see Information Sheet #3 for "corundum with glass filled fissures" and subsequent "corundum with/and glass") 2 Wording in parenthesis is optional. 3 © Swiss Gemmological Institute SSEF 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.

Page 1 of 2

Heating with surface diffusion (shallow)

Cr-diffusion treated Untreated (or heated) 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.& Detection+with+the+microscope+and+chemically+

surface diffusion! natural!

© H.A. Hänni, SSEF 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&.

Heating with beryllium diffusion (lattice, bulk)

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&!&

16! Detection of heating with beryllium diffusion

Detection of heating with beryllium diffusion

Be Al

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.&

Safe detection only with LIBS, LA-ICP-MS and SIMS

17! Multi-step Treatments: Creating a star effect

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

Internationally&harmonized&wording&for&the&conGidence&of&the&customers&!&

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&

18! Thank you for your attention

19!