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Jadeite Classification
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To maintain Hong Kong's position as an international jade trading centre, and to safeguard the interest of consumers and practitioners in the trade, the Hong Kong Jade & Stone Laboratory was established in 1993. With its cutting edge facilities, it provides a professional, fair, objective and accurate identification service for those in the trade and for the public.
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The laboratory is equipped with advanced facilities coupled with perfect security system and sufficiently covered insurance. The stringent cerfication process is HOKLAS-certified by Hong Kong Accreditation Service. The purpose is to safeguard fair trades and to protect the interest of the industrial players and consumers while boosting knowledge and confidence towards jadeite and gemstones.
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Jadeite Gallery
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Since it’s inception in 2004, Jadeite Gallery, organized by the Hong Kong Jewellery & Jade Manufactures Association (HKJJA), has been the vanguard of a jadeite renaissance. Making its continuous presence at the June Hong Kong Jewellery & Gem Fair and September Hong Kong Jewellery and Watch Fair, Jadeite Gallery showcases the magnificent ‘A’ jade (natural jadeite) from exhibitor.
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Moreover, HKJJA will execute a daily sample test by lots of ensure all exhibits in the Gallery are up to standard. Professional identification provided by the Hong Kong Jade & Stone Laboratory (HKJSL) will offer buyers on-site services.
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"A" Jade (Natural Jadeite)
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Refers to natural jadeite which is not subject to any form of chemical treatment except those traditional processes such as plum juice washing and wax polishing. These procedures are internationally recognized as standard practice and are not defined as "treatment" because the structure of the jadeite has not been damaged.
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"B" Jade (Chemically bleached and polymer impregnated Jadeite)
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Refers to jadeite which has been chemically bleached to remove the impurities. It is further rinsed with caustic soda and followed by impregnation of polymer to enhance its translucency. The structure of jadeite is damaged through this treatment and it will lose its lustre once the polymer deteriorates with the lapse of time. In addition, "B" jade cannot withstand heat and pressure.
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"C" Jade (Dyed coloured Jadeite)
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"B+C" Jade (Dye coloured and polymer impregnated Jadeite)
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Refers to "B" Jade which has been dyed to enhance its translucency and brightness during the polymer impregnation process.
Jade Testing and Identification
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Jade Testing and Identification
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The following two methods are widely deployed by the industry for jade testing and identification:
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1. Destructive
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There are two kinds of destructive testing used exclusively for academic research:
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Controlled heating: natural jadeite can resist heat up to 900 - 1,000'C, while B Jade will turn brownish at 400'C.
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Dissolution: the polymer in B Jade will loosen its structure and makes it susceptible to dissolution. Soaked in an appropriate solvent, the polymer in B Jade will gradually decompose and the remaining materal will end up in an opaque and clay-like state.
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2. Non-destructive
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Employed by laboratories to examine the following criteria:
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The physical properties of the tested jade item, such as refractive index, specific gravity.
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The colour of the tested item. A Chelsea colour filter, spectroscope and microscope will be used to identify and check whether it has been dyed.
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The presence of polymer. Using a ultra-violet light source, S.G. liquids, microscope and infrared spectrometer to detect whether the tested item contains polymer.
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Normally laboratories will employ the above 'non-destructive' method to examine the jade items for their clients and then issue certificates. Information on the certificates, as in the case of the Hong Kong Jade & Stone Laboratory, will usually include three sections, namely description, tests and findings, and conclusion.
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Description
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Shape
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Most commonly seen ar oval cabochons, bangles, pendants, or fancy shapes and carvings, etc.
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Weight
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Each piece is weighed on an electronic digital balance to the thousandth of a carat (ct).
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Measurements
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Dimensions (length, width, depth) are measured using millimetre as the unit.
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Transparency
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Degree of transparency is graded as follows:
1.
Transparent
2.
Semi-transparent
3.
Translucent
4.
Semi-translucent
5.
Opaque
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Colour
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Colour is measured according to the following standards:
1.
Evenness: colour distribution is described as even to uneven, in patches and/or veins and spots.
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Tone: depth of tone is described from light to dark.
3.
Hue: description of colour (e.g. bright green, green, greyish, white, lavender, red, orange, black, etc.).
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Tests and findings
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Refractive index
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Average refractive index for jadeite ranges from 1.66 to 1.68
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Specific gravity
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Average specific gravity range for natural jadeite will be 3.32 to 3.34 or more, while 3.30 or less for chemically treated jadeite.
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Fluorescence
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Object will eject visible light, namely long-wave and short-wave ultraviolet light, when subjected to ultraviolet radiation. Most of the natural jadeites do not release any ultraviolet light under this treatment. When a jadeite contains foreign bodies, weak chalky white/blue ultraviolet light will be shown, while chemically treated jadeite will release strong chalky white/blue light.
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Spectroscope
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Natural jadeite of bright green colour will show fine chrome lines in the red area of the spectrum, whereas a dyed jadeite will show a wide band in the red area.
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Texture
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1. By eye: it is described from fine to coarse.
2. By magnification: it is described as fibrous or granular or a combination of both.
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Chelsea colour filter
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Helpful in detecting green dye in jade. The item will appear reddish under this filter. It should be noted that this filter may serve as a reference guide only because it reacts to certain dye substances but not all.
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Polymer detection & infrared spectrum
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It can be detected that whether the tested jadeite has polymer or excessive wax. Chemically treated jadeite normally contains polymer.
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Remarks
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May include certain remarks like A Jade or B Jade
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Conclusion
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It states the identification of the material and whether it has been treated, The following four categories are classified as jadeite:
1. Natural jadeite
2. Chemically bleached and polymer impregnated jadeite
3. Dyed jadeite
4. Dyed and polymer-impregnated jadeite
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