Christies HK Jade - · PDF fileUV-Vis Spectrometer (natural colour vs dyed) FTIR spectrum...
Transcript of 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
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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
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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
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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)
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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.
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jadeite kosmochlor omphacite
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Solid soution
Kosmochlor
Omphacite Jadeite
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Na
Cr
Fe
Jadeite
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Jadeite
Thin section
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JadeiteSEM picture
SEM BSE picture
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Jadeite
Jadeite is often carved
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The green colour is due to chromium and iron
Jadeite
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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)
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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.
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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
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Serpentine
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Serpentine
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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
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Nephrite
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NephriteArt objects of historic periods
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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.
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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
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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.
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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!
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Colour description
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Colour distribution
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Jadeite Testing
Specific gravity measurementPolariscope examination
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Jadeite Testing
Jadeite granular texture
Polariscope examination
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Jadeite Testing
Observation of UV reaction© Swiss Gemmological Institute
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Jadeite Testing: UV-Vis
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UV-Vis spectrometer:From heavyweight......to very small.
Jadeite UV-Vis spectrum
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Fe
CrCr
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Jadeite Testing: Infrared
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Our recent acquisition,a portable FTIR spectrometer forgemstone testing (Bruker Alpha).
Jadeite infrared spectrum
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before treatment: A-jadeite
after treatment: B-jadeite
A-jadeite with finger fat
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Jadeite infrared spectrum
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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
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... eternal values
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Important jadeite jewellery
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SSEF launches new Jadeitereport in January 2009
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JadeiteTesting
SSEF will introduce a new and detailedjadeite report beginning of 2009.
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Thank you for your attention
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