Christies HK Jade - · PDF fileUV-Vis Spectrometer (natural colour vs dyed) FTIR spectrum...

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Jade

A presentation by Dr. Michael S. KrzemnickiSSEF Swiss Gemmological Institute

photos © mostly by Prof. H.A. Hänni, SSEFSeptember 2008

Jade (historical)In Asia the term jade was traditionally used for all kinds of carvings which nowadays aredistinguished into different minerals such as jadeite, nephrite, omphacite, serpentine a.s.o.

Only in the last 150 years, mineralogy established as a science and these different mineralscould be identified.

© Guillaume Soubira, 2006

© Swiss Gemmological Institute

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Jade sensu lato

The CIBJO recognises Jadeite-Jade and Nephrite-Jade as “Jade”, but no other minerals.

Jade is a term used basically for two minerals in theirmassive form, as polycrystalline quasi monomineralic rocks.Both are chain silicates:

Jadeite is Jadeite-Jade

Na Al Si2 O6

Pyroxene group

Tremolite-Actinolite is Nephrite-Jade

Trem Ca2 Mg5 Si8 O22 OH

Act Ca2 (Mg,Fe)5 Si8 O22 OH

Amphibole group


Jadeite


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Mogaung

Hopin

Mawsitsit

Kansi

Nanyaseik (ruby)

Sate Mu (Sine Naung)

Maingkwan (amber)

Kamaing

Makapin

Nyaungbin LakeIndawgyi

HaungpaMyitkyina

BURMA

Hweka

Mamon

Mt. Loimye(5124 ft)

Jade mining area

Ruby mining area

Amber mining area

Mandalay-Myitkina rail line

Burma

Lonkin

Hpakan


Burma

The origin of Jade

Uru boulder conglomerate

Mawsitsit

serpentinized peridotite

Jadeite Outcrops

sedimentary rocks (Tertiary)

Hpakan

Lonkin

crystalline schists

© R.W. Hughes


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JadeiteJadeite-Jade: Jadeite Na Al Si2 O6

R I (1.654 1.665 ) mean 1.66 S G 3.34 H 6.5 - 7 Double refractive aggregate reaction under the polariscope ( optically biaxial positive )

Colours : white, green, yellow, orange, violet, black, homogeneous to spotted or mottled

Chromophores: Cr, Fe, Mn Spectrum: Cr 438, 630, 650, 660, 690 nm

Degree of transparence: from opaque to near transparent

Structure: blocky to fibrous,

Treatments: B-Jade is impregnated with wax or epoxy resin

C-Jade is dyed

Sources : North Burma (Myanmar), Guatemala, Russia,

Absorptionspectrum ofemerald-green jadeite (Imperial Jade)


© Christieʼs Hong Kong

Fei Cui (Jadeite-Jade)

Kosmochlor

Omphacite Jadeite

Definition of Fei Cui (Jadeite Jade)after the Gemmological Association of Hong Kong

Fei Cui (jadeite jade) is a granular to fibrous polycrystalline aggregate. It is composed ofjadeite as major mineral. It may consist of other minor minerals such as opmhacite,kosmochlore, amphibole, and feldspar.


jadeite kosmochlor omphacite

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Solid soution

Kosmochlor

Omphacite Jadeite


Na

Cr

Fe

Jadeite


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Jadeite

Thin section


JadeiteSEM picture

SEM BSE picture


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Jadeite

Jadeite is often carved


The green colour is due to chromium and iron

Jadeite


Graphite inclusions may produce greyish and black jadeite-jade

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Lavender Jadeite-Jade

Jadeite of light purplish to violet colour is calledlavender jade. Some of this materialproved to be a mixture of jadeite with albite.Jadeite - albite assemblage (reflected light)


Nomenclature ?

The mono-mineralic composition may be quit and other minerals may form the rock.This leads to discussions about nomenclature: is Maw Sit Sit considered a jade?


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Maw Sit Sit

colour: light green to black, single colour or, spotted, mottled, often with black spots andwhite veins

density: 2.5 - 3.2 g/cm3 depending ofmineral composition

Refractive index : weak reading at 1.52

A complex rock from N-Burma underhigh pressure metamorphic conditions.

Maw sit sit contains minerals from thejadeite solid solution with cosmochlore.


Imitation of Jadeite

Dyed marble, quartzite, or glass may be misrepresented as jadeite© Swiss Gemmological Institute

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Dyed marble

dyed quartzite aventurine-quartzite

massive fuchsite

Imitation of Jadeite


Serpentine


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Serpentine


Prehistoric stone axe, found atLop Nor, Taklamakhan desertin the Xinjiang Province(northwestern China)

Nephrite JadeNephrite is a term used for fibrous Tremolite-Actinolite rock Tremolite Ca2 Mg5 Si8 O22 (OH)2

Actinolite Ca2 (Mg,Fe)5 Si8 O22 (OH)2

Amphibole, chain silicate ( biaxial negative )

R I 1.606 - 1.632 spot reading 1.62S G 3.00

colours: white, green, yellow, orange, brown, grey, black (depending on iron content or actinolite proportion)

Spectrum: Fe 460, 500, ev. 690 nm

Structure: fibrous, very dense, inclusions often magnetite or chromite

Deposits in China, Russia, New Zealand, Australia, USA, Switzerland, ...


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Nephrite

Cr diffusion around chromite inclusion

Thin section


Nephrite


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NephriteArt objects of historic periods


The Treatment of Jadeite

Treatments mainly affect colour and degree of transparency

Dyed jadeite jade (C-Jade)


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Treated Jadeite

Untreated jade is referred asA-jade.

Treatments mainly affect colour and degree of transparency. Natural Jade isoften stained by natural iron oxide. This brown colour may dramatically spoilthe otherwise good colour. Bleaching removes the brown, but leaves openpores along the grain boundaries. They have to get filled in order to improvethe appearance. Impregnation may be performed with colourless paraffin(wax) or epoxy (polymer, artificial resin). Such jade is called B-jade in thetrade.

Often the impregnation of bleached, porous jade is performed with fillerswhich carry dye to improve the colour of the jade. After treatment withcoloured epoxy or paraffin wax, the jadeite is called C-Jade (or B+C-Jade) inthe trade.


Treated Jadeite


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Treated Jadeite

During the bleaching with acids any residual iron-hydroxide is dissolved.The grain boundaries are open.

To enhance translucency, colour and stability, the bleached jadeite is afterwards commonlyimpregnated with wax or epoxy.

Untreated jadeiteClosed grain boundaries

400x magnification

bleached jadeiteOpen grain boundaries

400x magnification


Treated JadeiteOpen texture Closed texture

Iron stain

Open texture Closed texture


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Treated Jadeite

Green and violet dyed jadeite. The colour is concentrated in fissures and along grain boundaries.


Treated Jadeite

Dyed jadeite


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Treated JadeiteDyed Jadeite in different colours

Treated Jadeite

Coated with a green plastic lacquer


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Jadeite TestingSSEF Testing procedures

MeasurementsWeightDescription of colour, (colour prefix, saturation, tone)Degree of translucencyDegree of lustreDescription of texture

Specific Gravity (hydrostatic balance)Refractive index (spot reading with refractometer)Polycristalline anisotropic (Polariscope)Fluorescence (LW and SW UV-lamp)Chelsea Filter

Microscope (texture, polish, treatment, etc.)UV-Vis Spectrometer (natural colour vs dyed)FTIR spectrum (treatment detection , A-, B-, C-Jade)Raman microspectrometry (identification, treatment detection , A-, B-, C-Jade)X-ray fluorescence (chemical composition, chromium concentration)

Every jadeite is independently tested by at least two gemmologists!


Colour description


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Colour distribution


Jadeite Testing

Specific gravity measurementPolariscope examination


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Jadeite Testing

Jadeite granular texture

Polariscope examination


Jadeite Testing

Observation of UV reaction© Swiss Gemmological Institute

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Jadeite Testing: UV-Vis


UV-Vis spectrometer:From heavyweight......to very small.

Jadeite UV-Vis spectrum


Fe

CrCr

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Jadeite Testing: Infrared


Our recent acquisition,a portable FTIR spectrometer forgemstone testing (Bruker Alpha).

Jadeite infrared spectrum


before treatment: A-jadeite

after treatment: B-jadeite

A-jadeite with finger fat

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Jadeite infrared spectrum


before treatment: A-jadeite

after treatment: B-jadeite

A-jadeite with finger fat

Wax peaks in a IR spectrum of a paraffin treated jadeite

Jadeite Testing: Raman


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Raman spectra of Jadeite


... eternal values

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Important jadeite jewellery


SSEF launches new Jadeitereport in January 2009


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JadeiteTesting

SSEF will introduce a new and detailedjadeite report beginning of 2009.


Thank you for your attention


Christies HK Jade - · PDF fileUV-Vis Spectrometer (natural colour vs dyed) FTIR spectrum...

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Transcript of Christies HK Jade - · PDF fileUV-Vis Spectrometer (natural colour vs dyed) FTIR spectrum...