QUALITY ASSESSMENT OF NATURAL JADEITE ...jadeite jade is dedicated to the assessment of the...

GEMGUIDE - 1 - JULY / AUGUST 2020

INTRODUCTION

Most publications about jadeite grading discuss thevarious treatments but not the actual quality grad-ing of natural untreated jadeite. While there are

standards for quality grading of jadeite jade (Cantonese: FeiCui) in Hong Kong and in mainland China (Mandarin: Fei Tsui),there are only a few publications about the subject in non-Chinese language.

The author offers a simplified step-by-step method to assessthe main quality parameters of natural un-treated jadeite, alsoknown as “Type A” in the trade. This systematic approachforms the foundation for a consistent appraisal. The wholeconcept involves the following steps:

Step 1: Identification of the gemstone species.Step 2: Identification of treatment(s).Step 3: Quality assessment:

QA1a) Judging the quality of the base: grain size and diaphaneity.QA1b) Judging the evenness of the texture: look for textural imperfections and structural flaws.QA2a) Judging the clarity: extent, size, and color of inclusions.

QA2b) Judging the purity: presence and type of fissures and fractures.QA3) Judging the type of base: classification of thebase and luster.QA4a) Judging the color: hue, tone, saturation. If present, identify secondary color.QA4b) Judging the evenness of color.QA5) Judging the make: shape, proportions, outlines,polish quality.QA6) Judging the volume: volume is better than size.

Step 4: Valuation and appraisal.

This article focuses on the assessment (processes listed asQA under step 3) of nine parameters that define quality andvalue of all color varieties of natural Burmese jadeite. How-ever, it is advised to previously identify the gemstone speciessubmitted for appraisal. Standard gemological tools might besufficient for an experienced gemologist to support a reliableidentification, but one should keep in mind that jadeite is apolycrystalline aggregate which is part of a solid solution se-ries with omphacite, kosmochlor and aegirine, and that am-phibole-group minerals and plagioclase feldspar (e.g., albite)might also be part of the stones’ composition. Thus, the ag-

QUALITY ASSESSMENT OF NATURAL JADEITE:PROCESS AND TIPS FOR APPRAISERSRoland Schluessel, FGA, DGemG

Most retailers and appraisers in the Western World lack the knowledge to judge the quality parameters andvalue of natural untreated jadeite. This is because natural jadeite material in all qualities is scarce in the westernmarketplace, and because they lack literary references to rely upon.

FEATURE ARTICLE

FIGURES 1 AND 2. Selections of green and purple natural jadeite cabochons from Burma/Myanmar. Jadeite from the purple series usually have a coarsergranular texture than green and colorless to white jadeite. Photo by Roland Schluessel.


ASSESSMENT OF NATURAL JADEITE

gregate can be monomineralic or polymineralic. If the ap-praiser has access to a Raman instrument, they should testdifferent areas of the stone and define the dominance; a pre-dominance of 80% jadeite is required to call it jadeite jade.But traditional gemological equipment can be helpful. For ex-ample, the ultraviolet light source can be used to spotfeldspar areas in the stone’s composition. Many feldspar min-erals react to UV fluorescence. Green and gray to blackjadeite is inert, other color varieties can show a weak fluo-rescence, or moderate fluorescence as observed in the col-orless and white to off-white varieties. Be careful as wax,some polymers/resins and some color dyes do fluoresce too!

Careful examination of the texture can provide valuable infor-mation too. The granular texture of omphacite looks more“sugar-like” than in jadeite; however, this is not helping in iden-tifying the respective percent-constituents of the jade item.

The identification of treatments in jadeite is as tricky as themineralogical identification. Some treatments such as “bulk”impregnation combined with color dye are readily detectable,but identification of surface impregnation with modern poly-mers, and detection of color origin in some purple jadeite re-quire advanced gemological equipment such as FTIR, Ramanand UV-Vis. Figures 1 and 2.

ASSESSMENT OF QUALITY PARAMETERSThis chapter focuses on jadeite jade’s primary colors, namelythe green, purple and colorless to white series (blue and pinkare included in the purple series). Mainly because these va-rieties represent the vast majority of jadeite material ex-pected to be submitted to an appraiser in the westernmarkets, but also because there are some differences in thequality features of jadeite jade with secondary colors, largelyrepresented by the yellow-red-brown series, and gray toblack, which owe their color to various amounts of inclusions.

The first two steps of judging the quality parameters ofjadeite jade is dedicated to the assessment of the “base.”The base is the term used to describe the body of the stoneconsidering its “consistency.” The base, also known as fabric,includes the grain size, texture compactness, texture even-ness and diaphaneity.

QA1a.The assessment of the base quality involves principallythe grain size and the diaphaneity. There is a direct relation-ship between base quality and diaphaneity of jadeite. Thefinest grains are generally associated with the tightest tex-ture, while the very coarse grains are characterized by aloose, much more porous texture. The finer the grain is, thehigher the degree of diaphaneity, and the greater the trans-parency is, the higher the value is.

Coarse grain applies to grain sizes exceeding 2 mm, they areevident to the naked eye. Medium-sized grains measure be-

tween 0.5 and 1 mm, they are barely visible to the unaidedeye but are identifiable with a handheld 10x magnifying loupe.A granular texture with grains measuring 0.1 mm and belowis considered as very fine to extremely fine. A microscope isrequired to observe this finest microcrystalline structure.

Fine to extremely fine grain sizes are best seen under themicroscope while experimenting with fiber-optic illumina-tion from all sides, including overhead illumination to ex-pose the stone’s surface texture. Inside the stone, it is thereflecting interstitial material that is most evident whenusing oblique fiber-optic lighting (Figure 3). The fibrous tex-ture is best detected in transmitted light while playing withthe iris diaphragm of the microscope or with oblique fiber-optic illumination, combined with the “shadowing” tech-nique to increase contrast. Figure 3.

The degree of diaphaneity should be rated in transmittedwhite light. A black line on a slice of glass can be helpful tomake decisions in transparent, sub-transparent and translu-cent jadeite. Any color of jadeite with a high grade of trans-parency fetches high prices, but its diaphaneity is notcomparable with the transparency of a faceted monocrys-talline gemstone such as rock crystal or sapphire. Gem-qual-ity jadeite is comparatively semi-transparent/sub-transparentat best.

Once the observations are made, the author suggests usingthe Diaphaneity—Texture Chart (figure 4) and to mark thefield that corresponds to the jadeite item currently examined.The table emphasizes areas of possible texture-diaphaneitycorrelations, and excludes areas of impossibility, e.g., acoarse granular jadeite aggregate can in no way be transpar-ent (= “glassy”). Figure 4.

For the steps QA1a and QA1b it is of utmost importance tomake full abstraction of all other quality features, especially

FIGURE 3.The visibility of single grains and their arrangement is eased bythe strong reflection from interstitial material. Field of view 1 mm. Photomi-crograph by Roland Schluessel.


color. This seems difficult at first, but the appraiser has toimagine the jade item as being a colorless to white ice cube,without color and without considering fissures, inclusions,shape, polish quality and volume. Failure to do so will resultin imperfections to be assessed multiple times.

QA1b. The evenness of the texture is still part of the basequality. The appraiser must look for textural heterogeneities

and structural flaws. This is usually done witha 10x magnifying loupe and a flashlight thatis not too powerful: 90 to 110 lumens is ap-propriate for cabochons and beads, largerstones require more power, especially to as-sess the rough. Jade experts often take ad-vantage of a simple contrast enhancementtechnique by placing a metal blade betweenthe stone and the light source to increasecontrast.

Each piece of jadeite jade is different, whichrequires some creativity from the gemologistappraiser. In some instances, the author sug-gests using polarizing filters with the micro-scope or to observe the stone in a water cell,with or without polarizers; a traditional color-less champagne or wine glass with somewater works best for average-sized cabo-chons and beads (Figure 5).

As the term suggests, textural hetero-geneities and structural flaws must be limitedto the texture consistency of the base; theyare imperfections that are part of the fabric.A noticeable uneven mixture of fibers andgrains can reduce the uniformity of the base,and structural veining and/or micro-shear

bands (R. Schluessel 2018) can run through the stone, dimin-ishing the quality of its body. But fissures, fractures, and in-clusions should not be assessed here. As a rule, structuralimperfections usually share a similar color hue as the base,inclusions do not! Imagine an apple cut in half; the fleshshows some heterogeneities that can be considered texturalor structural marks, but the few dark colored seeds would beinterpreted as inclusions (see QA2a).


FIGURE 5. Immersion in water emphasizes the textural inhomogeneities ofthe base. The fabric of this jadeite cabochon is signed by micro-shearbands. Photo by Roland Schluessel.

FIGURE 6. Plotting diagrams for the analysis of the base. The green dia-grams serve as examples to describe a slightly uneven texture. The whiteones are for actual plotting. Diagrams by Roland Schluessel.

FIGURE 4. Practical chart for judging the texture–diaphaneity relationship of the jadeite’s base.Chart by Roland Schluessel.


The author recommends using simplified plotting diagramsto record textural imperfections and to assess their extentand size (Figure 6). Record position, as well as surface and/orvolume compared to the stone’s size. The plotting diagramsshould mirror textural imperfections as seen from the domeof the cabochon. Skilled jade cutters place “weak” texturedareas at the lower part of the cabochon; this is one of theseveral reasons why it is so much rarer to find jadeite beadsand bangles with a very fine fabric. Figures 5 and 6.

QA2a. Minerals that are not part of the jadeite jade’s compo-sition are regarded as inclusions. These usually have a differ-ent color hue than the polycrystalline base and occur asisolated crystallites or in small clusters. They can be black,gray, dark brown, or white. Tiny colorless to white mineralconcentrations that resemble cotton balls are called “pollen”(Figure 7). As long as they are small, they remain the leastdisturbing type of inclusion because they are often only seenin strong oblique light (e.g. obliquely held flashlight). Somesmall pollens are acceptable in fine translucent vivid greenjadeite known as “imperial jade.” Black inclusions are themost undesirable ones, especially in a lighter color and col-orless to white base. To effectively judge the degree of clarity,the appraiser must consider size, extent, color, and positionof the inclusions. The author recommends using a second setof plotting diagrams to record them. Figure 7.

QA2b.The author separates purity from clarity because purityhas a profound symbolic significance in most Asian culturessuch as Chinese, Japanese, and Indian. Fissures and frac-tures, popularly called cracks, detract from the purity of ajadeite item. In Chinese philosophy, jade is the “Stone ofHeaven,” it is the link that connected Earth and Heaven, thebridge from life to immortality. The presence of a fracture isinterpreted as lack of purity, and a conspicuous fissure cancause the jadeite item to be unsellable, even if it does notweaken its durability. The same plotting diagrams can be usedfor clarity and purity, for detected inclusions, fractures andtheir respective color(s), size and position to be labeled ac-cordingly. Figure 8.

QA3. Identifying the base category can be a little confusingbecause it is a mix of several features; the type of texture,including grain size and diaphaneity, together with the typeof luster define the base category. Independently of the color,jadeite might look wet, waxy, dry or oily, combined with a de-gree of diaphaneity, e.g., translucent oily, dry opaque, etc.

Since the type of base applies to all colors, it is importantto make full abstraction of the color. Again, imagine a pieceof transparent colorless to sub-translucent white ice. Thesix most occurring base categories are from the highest tothe lowest quality: glassy, icy, oily, cooked lotus root, peaand porcelain (Figure 9). A “pea” base is built up by coarserounded grains that resemble peas. Thus, you might en-counter white pea, green pea and other pea colors. A

“porcelain” base has an opaque to nearly opaque medium-fine granular texture resembling “flat-white” milk or chi-naware. It shows very low contrast and appears dry. But,when it is sub-translucent and white with a gelatinous typeof luster, it is called “nor” (Figure 4) and looks like stickyrice. In case of doubt, the author recommends describingthe grain size, the degree of diaphaneity and the type ofluster: wet, waxy, oily, dry.

To practice, the author suggests describing fruits and vegeta-bles. Look at them with and without flashlight and try to over-look the color. Occasionally, some fruits like apples, pears andtomatoes are waxed in order to improve their attractivity onthe shelf, check for the oily shine. Watermelon has an opaqueoily skin; peas look dry opaque; bell peppers and grapes are“low icy.” Figure 9.


FIGURE 7. “Pollens” look like minuscule cotton balls or cumulus clouds.Field of view 1.5 mm. Photomicrograph by Roland Schluessel.

FIGURE 8. Diagrams for the plotting of inclusions and/or fissures. The greendiagrams serve as examples, while the white ones are for actual plotting.Diagrams by Roland Schluessel.


QA4a. After these several steps, the appraiser can now takea close look at the stone’s color. The author strongly advisesnot to use terms such as “apple green,” “spinach green,”“moss in snow,” “flower green,” etc. The jade trade appliesseveral hundred terms to jadeite jade of the green seriesalone. Instead, the use of the color nomenclature based onthe Munsell color system provides the most accurate colordescriptions. Color hue, tone (value), and saturation (chroma)suit very well to assess all colors of jadeite. If present, thesecondary color(s) should be identified and mentioned inde-pendently. Color modifiers in green jadeite are blue and yel-low, while the saturation modifiers are gray and brown. Thesaturation modifiers in jadeite from the purple series are blueand yellow too, but the color modifiers are blue and red.

Judge the color in daylight around noon. Many colors experi-ence a color shift and/or increase in intensity when moved toincandescent light, especially jadeite from the purple and redseries. A combination with a color system such as World ofColor™ (Figure 10), or GemDialogue™ is recommended butensure that your color description matches the referencenumbers and definition of the color selection in your systemof choice. Mention the undertone (secondary color and colormodifier) additionally. Thus, the color description of a greenjadeite cabochon could be as follows: Slightly yellowish greenof medium-strong color saturation with very slight brownishsecondary color and very slight grayish tone. Saturation and

brightness are interconnected. Termslike bright, dull, vivid, vibrant can beadded when appropriate. Figure 10.

QA4b. The evenness of color is a signif-icant part of the color description. Evenlycolored high-quality jadeite cabochonsare scarce, even rarer are uniformly col-ored beads, but bright green bangleswith a good color distribution are soscarce that they fetch prices in the mil-lions of dollars.

Only the color distribution is judgedhere, textural/structural heterogeneitieshave been previously assessed. The ap-praiser shall identify the extent of colorthat differs from the dominant color ofthe jadeite item by expressing it as: e.g.,slightly uneven with dominant 80% and20% lighter; or uneven with 60% domi-nant, 30% lighter and 30% darker. Aplotting diagram as show in Figures 5and 7 can be helpful to record the wholepart above the outline of a cabochon;beads and bangles must be evaluated allaround.

Color evenness applies to “mono-colored” jadeite. It can bea green jade cabochon with some areas of darker or lightercolor, or a zone tinted by a secondary color. Multi-coloredjadeites are classified in different varieties, and the color de-scription indicates the multi-color nature of the material. Asymmetrical arrangement of color patterns within a singlejadeite item is more valuable than random multi-color spotsor patches, especially in multi-colored bangles.

QA5. The quality parameters for the “make” are defined byChinese philosophical norms for beauty and shape, influ-enced by tradition and feng shui, and by volume (refer to


FIGURE 9.The classification of the base combines texture and diaphaneity, but not color. Without con-sidering color and clarity/purity factors, the quality of the base decreases from glassy, being the mostvaluable, to porcelain, being the least desirable. Chart by Roland Schluessel.

FIGURE 10. Burmese jadeite cabochons on the 2.5G color reference pagefrom the World of Color™ system developed by Gemworld International.Photo by Roland Schluessel.



Sample appraisal report by the author.


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AQ6). The make includes thickness, proportions, outlines,symmetry and polish quality.

Cabochons are ideally cut as double-cabochons, also knownas double-convex cabochons, with a high rounded dome ap-proaching the thickness of half a bead; the bottom part, belowthe outline, should be convex with a depth varying between10% to 20% of the cabochon’s dome. This is important innon-opaque jadeite because the convex bottom reflects lightback to the upper central part of the dome, thus intensifyingthe color. A cabochon measuring less than 40% height fromthe outline to the top is considered too flat; more than 60%is too high. The cabochon can be round, but oval is moreprevalent; the most desirable length to width ratio is ca.1:1.20 to 1:1.40. The other “make features” like symmetryand polish quality are quite similar to other cabochon cutgemstones. If an antique-like patina does not provide a valuepremium for history/antiquity, the stone can be re-polishedto the best possible shine acceptance for that base quality.Be careful as artificially “aged” jade is plentiful on the mar-ketplace. Only jadeite with a tight and very fine granular tex-ture accepts the sharpest polish, exhibit the strongest lusterand can reveal the most sought-after inner glow known as“Ying-effect” (see “Ying-effect;” R. Schluessel 2018).

QA 6. Because bright and intense colors usually occur inveins, gem-quality green and purple jadeite is valued accord-ing to the three-dimensional volume, rather than by size. Achunky translucent bright green jadeite item is worth consid-erably more than a much larger thin slab. This is one of thereasons why jadeite is valued per piece and not per carat.

Step 4: This last step includes the valuation of the item andthe scripted content of the appraisal. The simplest way tocome to a quality–value conclusion is to list all quality param-eters that were previously assessed and to subtract percent-ages for the proportional deviation from the optimum. Inother words, to penalize each imperfect quality feature withthe appropriate discount percentage, like we are used todoing with the cut grade and fluorescence of diamonds.

For jadeite, value indications in the form of a pricelist remaina dream. Nevertheless, the author is providing an example ofa state-of-the-art appraisal for a jadeite item (see box on pre-vious page). Like an appraisal of a jewel set with a 2 ct color-less to near colorless round brilliant cut diamond, where allmeasurable and visible quality features are documented

and/or graded, an appraisal of a colored gemstone, includingjadeite, should be carried out with the comparable gemolog-ical and professional standards. While it can never be wrongto document everything that is observed about the gem-stone, the appraiser needs to be aware of his own limits,which, in case of a non-jadeite-specialist, are usually ex-ceeded when it goes beyond empirically descriptive features.

CONCLUSIONSThe appraiser should abstain from mentioning any terminologythat might suggest a variety. An error in variety identificationcan lead to huge value discrepancies. Only highly experiencedjadeite specialists are able to accurately identify jadeite vari-eties. Instead, a systematic description of everything the ap-praiser can see, will result in a best possible appraisal.

Judging the quality of gem jadeite is one of the most difficulttasks in gemology. But if thoroughly executed, it can behighly rewarding. Jadeite jade experts are very scarce in theWestern World and no gemological laboratory provides qual-ity grading of jadeite. One has to be fully aware that it is notpossible to compile all the data to create a dependable pricelist for jadeite; the combination of base categories and qual-ities, color varieties, clarity and purity grades, cut ratings, pro-portions and volume would result in thousands ofpossibilities. However, a meticulous assessment of qualityparameters as described here, forms a solid background toapproach the value of a jadeite item. Thus, some training andpractice will provide you with opportunities to request well-deserved compensations for reliable appraisals of this fasci-nating gem material. u

About the author. Roland Schluessel is co-owner of Pillar &Stone International, Based in Tiburon–San Francisco, Califor-nia. The wholesale company specializes in fine coloredgemstones and natural jadeite.www.pillarandstone.com

REFERENCESRoland Schluessel (2018). The Jades of Myanmar/Burma.Abstract from the 2017 World of Gems Conference,Chicago. GemGuide March/April 2018, Volume 37, Issue 2,pp. 4-8. Gemworld International; Glenview, Illinois.

Ou Yang Chiu Mei and Humphrey Yen (2015). Fei Cui – Jade: A Stone and a Culture. Shanghai Translation PublishingHouse; Shanghai, China.

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