Category Archives: Colored Stone grading system

Gemstone Cut Grading; Distinctions Without a Difference II

by Richard W. Wise, G.G.

Of Tilt-Windows, Off-center culets and other minor issues:

The image of the gem quality 1.44 carat alexandrite might lead the uncritical observer to conclude that the gem is windowed. What the gem is actually exhibiting is some extinction beneath the table. In a perfect world, both are minor faults, but we are talking about the rarest gem on earth. In the world of true rarity, beauty not mathematical perfection of symmetry is the ultimate criterion.

The first time I ever heard the term tilt-window was on the Pricescope forum. As you know, a window is a part of the gem when viewed face-up that exhibits transmitted light. Windows are almost always found right beneath the table. A quick test is to place the stone over a piece of newsprint. If you can read the print, you are looking through a window. Windows are the result of a shallow pavilion, a too shallow depth to width ratio. Windows are considered faults because they are a portion of the gem that does not sparkle.

Gem cuts are designed and engineered to be judged face-up with light perpendicular to the table. Tilt the gem away from the perpendicular and every gem other than a briolette will exhibit a window. Ironically the more precise the cut, the more likely the gem is to window when tilted as little as five degrees from the perpendicular. Some gems, particularly those with a bit of fat around the pavilion, may exhibit some brilliance when tilted as much as ten to fifteen degrees from the perpendicular. What cannot be eliminated must be embraced. A tilt window, forgetaboutit!

Grading; From Minus To Plus:

Gems with bulbous pavilions are often criticized for being overweight, meaning that the stone’s face is smaller than it would be if the stone was perfectly cut. The irony here is that such stones may actually exhibit a greater arc of brilliance which contributes to the beauty of the gem. Once the eye is four to five feet from the gem, the overall brilliance becomes the real issue, not the stone’s mathematical diameter. Broader bellies also extend to the length of the light path and may enrich the color (hue, saturation and tone) of the gem.

In another Pricescope thread, one ubiquitous poster put a link to an alexandrite (pictured above) on my website and criticized me for the failure to disclose an off-center culet. How did this forum member determine that the stone had such a terrible fault? The page included a side view image of the stone face-down. If there was an attempt to hide the fault, it was hidden in plain sight. http://www.rwwise.com/products/id,255 Unfortunately her interpretation of the image was quite wrong. The stone does not have an off-center culet. What the forum member saw was a very minor symmetry fault, one side of the pavilion has a slight indent coupled with a tilted crown which when placed on a flat surface caused the culet to appear off-center. And if the gem did have a slightly off-center culet, so what! We are talking about one of the earth’s rarest treasures, a gem quality alexandrite!

Each Gem Is an Individual with a distinct personality and should be judged on its merits:

Gem aficionados usually begin their love affair with the colorless diamond. They learn the famous 4 C’s and attempt to apply those criteria, namely color, clarity cut and carat weight uncritically to colored gemstones. As I have said elsewhere all Cs are not created equal. In the connoisseurship of colorless diamond, cut is the 1st and most important criterion. Diamonds have no color, they are all about brilliance and sparkle, so naturally cut, which delivers sparkle is the most important single criterion. I knew a neophyte jeweler once who was not satisfied with eye-flawless sapphires, he demanded that all of his sapphires be flawless under 10x magnification. The problem, without inclusions it is almost impossible to determine if a stone has been enhanced and determination of geographic origin is absolutely impossible.

Colored gemstones as their name suggest are all about color and cut is, at best, a secondary consideration. An off-center culet in a diamond would be a major symmetry fault and materially effect price. In a colored gem, an off-center culet in and of itself is a minor fault which has no effect on price. Why do such things exist? A culet might appear off-center for a couple of reasons. The lapidary may have removed a potentially eye visible inclusion or have placed the culet slightly askew to smooth out color zones so that the zone does not appear in the gem when viewed face-up.

It should be remembered that colorless diamonds are not truly rare. The introduction of cut and clarity scales that have nothing to do with beauty are more about creating the appearance of rarity than the thing itself. The connoisseurship of gemstones requires discernment and careful contemplation. Gems cannot be accurately graded by image. The aficionado should beware attempts to reduce it to a formula or a check list.

Gem Cut Grading; Distinctions Without A Difference

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The diagram shows the proper angle for viewing an asymetrical gemstone. The bottom half of the gem is evaluated, the gem is then turned 180 degrees and the other half is judged for percentage of brilliance, the two percentages are then totaled.

$This matche pair of carat sized blue sapphires exhibit off-axis refraction also known as extinction. The dark areas move as the gem moves partially defilning the positive areas of scintillation$

This matched pair of carat sized blue sapphires exhibit off-axis refraction also known as extinction. The dark negative areas move as the gem moves partially defining the positive areas of sparkle (scintillation) in the gems

I wandered over to one of the major gem forums this morning. One of the members was talking about a phenomenon he called “shadowing.” This poster defines shadowing when a gemstone exhibits brilliance across half the stone when the stone is held off axis, that is not perpendicular to the light source, he was looking for a cure.

A Non-Issue:

This is a good example of a non-issue. Non-symmetrical cuts, rectangle, oval, pear viewed under a single beam light source will always show brilliance across half the face of the gem when the stone is tilted away from the perpendicular. Why, because the gemstone is not symmetrical and therefore treats light in a non-symmetrical fashion. In the cuts just mentioned, some facets particularly the pavilion facets which are responsible for delivering brilliance, cannot be uniform. Some are larger, some are longer therefore light hitting these facets will refract in an irregular fashion. Symmetrical cuts, rounds and square cushions, by contrast have uniform facet patterns and do not suffer this phenomenon.

For this reason, asymmetrical gems are graded under a single light source, viewed at at a 45 degree angle away from the light source angled toward the eye. At this viewing angle, half the gem, the bottom half is potentially brilliant. The percentage of that half is then compared with the other half when the gem is rotated 180 degrees and viewed a second time. Add the relative percentage of each half and voila you have the total percentage of brilliance. In colored gemstones, 80% brilliance is considered excellent which means that at any given time, 20% of the gem will exhibit extinction.

One trick for viewing the brilliance of the entire stone at once is the use of sky light. Turn your back to the sun and view the gem at the same 35 degree angle toward the eye. In this position the light filtering around the body of the viewer should light up the 100% of the gem. Any lack of brilliance in this position is a fault and should be subtracted from the theoretical 100% to arrive at the percentage of brilliance. In most cases, gem photographers correct for this phenomenon by photographing gems with non-symmetrical outlines by using multiple light sources.

A Little Extinction Contributes To A Gem’s Beauty

Extinction is another much misunderstood phenomenon. I am often asked, particularly by members of this forum, if a particular gem shows extinction. First lets define our terms, what is extinction. This phenomenon is caused by off-axis refraction. When light enters a gemstone, it enters the crown and reflects internally off the pavilion (back) facets and eventually back through the crown to the eye. Inevitably some light refracts at an angle that is not toward but rather away from the eye, the greater the angle the more extinct it becomes, in a tonal continuum from gray to black.

All faceted gemstones without exception exhibit extinction, no extinction, no scintillation. the great German philosopher Hegel said determinatio est negatio. which when reduced to simplest terms means g all positive requires a negative. Sweet has no meaning without salty, good does not exist without evil, etcetera. So too with gems. Scintillation, sparkle is the result of light being broken up into pieces, tiny scintillas of light that are refracted back to the eye in little pieces. Between those pieces is darkness, extinction. Want a gem to light up like a flashlight with no sparkle, eliminate extinction. Some degree of extinction is therefore required as contrast.

Extinction As A Fault:

Extinction can have other causes as well, dark is the absence of light. Gems lacking transparency will often show what one of my clients once called a “heart of darkness” at the center of the gem beneath the table. This is particularly prevalent in sapphire and the cutter will often cut a window to let in light through the culet, the apex of the cone shaped pavilion of the gem. So while some extinction is desirable, in fact necessary to the beauty of the gem, large areas of extinction are a definite and definable fault.

Evaluating Gem-e-Wizard; Gem Grading/Pricing Software

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First off, Gem-e-Price is the first grading/pricing software that I have evaluated and working with it was a lot of fun. With the recent addition of colored diamonds, Gem-e-Price is now able to offer a price structure for just about all species and varieties of colored gemstones.

Gem-e-price offers three ways to approach the evaluation/pricing process. I say evaluation because, although gem-e-price is sold as pricing software, the ability to select quality is a necessary precondition for determining price.

Ease of Use:

The software is easy to use. First you are presented with a fairly clean screen with buttons and drop boxes. There are three tabs; Fancy Search, Price List and Price Calculator. The default screen, Fancy Search allows you to select a gem variety, size, shape, weight, clarity, treatment.

Gem-e-price Home screen showing range of colors in yellow diamond.

Unfortunately it didn’t take long for the first bug to appear. Once you select “color” (primary hue) and “modifier” (secondary hue) and move on to shape, you quickly realize that though you can select your shape from a graphic series, only two shapes will actually appear in the gallery, select round or square cushion, choose any other shape and square cushion is shown.

The images, which in the colored diamonds section covers the basic grades, fancy through fancy dark, are not pictures of actual gemstones or photographic images at all, they are graphic representations. When I first saw these during the introduction of gem-e-price for colored gems, I referred to them as grading by cartoon. However, one function of the software helps overcome this lack of veracity to some degree. Once the color has been selected, say yellow, the “Fancy Ruler” button to the right will take you to a screen with a spectrum representing all colors, from there a “Select Color” button in the center of the screen takes you to a new screen with all permutations of the given color (hue): brownish yellow, brown yellow, orangy yellow and so forth. You get a good relative overview of what the graphic range is supposed to represent and is useful for honing in on the appropriate nuance of color.

Gem-e-price screen showing range of primary and secondary hues in pink diamonds.

It also provides you with a more or less universally accepted color descriptive shorthand, e.g. VpB (vivid purplish blue). I should add that you are able to upload, at the home screen, an actual image of the diamond that you wish to compare and that image follows you from screen to screen.

Nomenclature Issues:

Is the pricing accurate? As Shakespeare said, “aye, there’s the rub.” The answer is yes, no and sometimes. I compared the Gem-e-price with a couple of my own diamonds, then called colored diamond expert Stephen Hofer author of Collecting and Classifying Coloured Diamonds and compared various price lists, pink, gray and blue diamonds generated by the Gem-e-price software. The prices made no sense at all until in a conversation with Gem-e-price developer, Menahem Svedermich, he revealed that the price is pegged fairly low. This will require a bit of explanation.

The point I make in my book, Secrets Of the Gem Trade, is that all fancy vivid diamonds are not created equal. GIA’s colorless diamond grading system has 24 grades, the GIA colored diamond grading terminology has only between 5-7 depending upon the hue. These are fancy light, fancy, fancy intense, fancy vivid, fancy deep and fancy dark. In the vivid category, for example there can be high, medium and low vivids depending upon the saturation/tone of the hue. Gem-e-price assumes a 1-5 saturation grid at each level and pegs its price to level 2. Why not the median? Good question! Well, one week later, Gem-e-price has been updated, it now sports three price levels for each color grade, Regular, Fine and Extra-fine categories and these have helped to better define price levels.

Pricing Accuracy:

With Hofer’s help I took a look at a one carat Fany Intense Pink diamond( FIP). A two thousand dollar spread, in pink diamonds, hardly worth mentioning, the price was spot on. I then went to a 0.70 FVY-O from my own inventory. This is a problem stone, The GIA grading report calls it Y-O, to me its a orangy yellow (oY). So, I tried it both ways. The Yellow-Orange price was way out of the box, the Orangy-Yellow was pretty close to my actual cost. Next I tried a 1.75 Fancy Intense Blue IF which Hofer described as a top stone. The Gem-e-price was between under Hofer’s price by between 100-200,000 per carat—sounds like a lot but we are talking blue diamonds here so it is fair to say that Gem-e-price is in the ballpark. I did some further work, switching over to colored gemstones I priced out emerald, ruby and sapphire. The emerald and sapphire prices came out in the zone, the ruby price, we are talking super-unheated-gem in one carat sizes came out very high. I asked Antoinette Matlins author of the second best book on colored gemstones—opps there goes my Bonanno award—she checked my price and reported results that were similar to mine.

Overall Evaluation:

Overall I like it. Is it perfect, no! It is designed for professionals, in the hands of someone without a wealth of experience it could be a potential disaster, but then what isn’t? Gem-e-price is a useful tool, its got a few bugs, but it is getting better, Svedermich and his team made adjustments as I worked and will, I am sure, continue to improve the product. I like the price grids! A subscription with monthly updates is $300.00 per year and, in my opinion, well worth the price.

Gem Grading: The Death of the Lightbulb and Other Brilliant Ideas

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Color temperatures a various types of lighting. 5500-6500 is the Kelvin temperature of daylight. GIA uses a 6200 Kelvin light source for diamond grading.

New Technologies May Require Changes is How We Look At Gems:

In 2007 amid little fanfare, Congress passed a law that required that the efficiency of that iconic household standby, the incandescent light bulb, be improved or perhaps accept its doom. The bulb has been around a long time and the technology has remained virtually unchanged since it was invented by Thomas Edison in 1881. Turns out the old bulb is a real energy waster, only 10% of the energy used is given off as light, the rest is dissipated as heat. Though some called it the death of the incandescent light bulb, Congress merely dictated an increase in efficiency, 20% by 2014, 60% by 2020.

Though the efficiency standards do not state what is allowed, such a dramatic increase in efficiency is bound to require new technologies which are likely to mean changes in the light spectrum produced by whatever technology replaces the old standard. No one has given much thought to the consequences this will have in the gem trade. The new standards are scheduled to take effect this January.

In the evaluation of quality, gemstones have been traditionally viewed under two light sources, noon daylight or more lately daylight equivalent fluorescent lighting and plain old incandescent (in the 19th Century it was candlelight). A stone that looked good by day but muddied up under the lightbulb is taken to be inferior to one that holds its color in both lighting environments. In 2003 I published a book, Secrets Of The Gem Trade, that divides gems into daystones and nightstones. The terms refer to gem varieties that look best under a given source. This seemingly bright idea may mean dramatic reductions in oil imports, but wait! What about the gem business, what’s a connoisseur to do?

The Tea Party To the Rescue:

Well our worries may be over, just last week the House passed legislation to deny funding to the law. Apparently the bill’s original Republican sponsor, Texas Representative Michael C. Burgess had an epiphany. He has seen the, ah, light. “The government has no right to tell me or any other citizen what type of bulb to use at home,” no matter how much energy it might save says Mr. Burgess. We have the right to waste all the energy we like in the privacy of our own bedrooms, says so in the scriptures.

But seriously folks! Sooner or later, new, more efficient types of lighting are bound to replace the old standby. Will there be a new standby? Probably not. We are pretty much at the point where the type of lighting used will be dictated by the setting that it is used in. Call it dial a light! At that point will gem grading light be standardized. To some degree it already has. Most laboratories use some artificial version of daylight. The Gemological Institute of America (GIA-GTL) uses a 6200 fluorescent bulb, American Gemological Labs uses a 5500 Kelvin bulb. What is the next step? Stay tuned to GemWise.

Book Review: The Colour of Paradise, The Emerald In The Age of Gunpowder Empires

Kris Lane

The Colour of Paradise, The Emerald In The Age of Gunpowder Empires

280 pages including appendices

ISBN: 978-0-300-16131-1

The history of the gem trade is a difficult research topic because gemstones are very small objects of great value that have been highly sought after for millenia by rich and powerful people looking for wealth that was portable and easily concealed. The trade itself has been controlled for centuries by minority groups, often oppressed minorities, Jews, Armenians and Indians for whom secrecy was a proven form of self preservation. Kris Lane is a historian, a Professor of History at the College of William and Mary. In The Colour of Paradise, Professor Lane focuses very well honed research skills on the history of the emerald, one of the rarest, most mysterious and highly valued of all gemstones.

The book contains no particularly major revelations. Most historians of the trade are aware that India’s so-called “old mine” emeralds were, in fact, Colombian emeralds imported by the Spanish into India in the Sixteenth and Seventeenth Centuries. Lane’s contribution is to meticulously document both the early history of Spain’s brutal exploitation of Colombia’s indigenous people and its gem wealth. He gives us a well documented overview of early trade routes and uncovers some very interesting and original information concerning 16th Century production; methods and emerald values.

Lane begins with the 16th Century and follows emerald production in Colombia right up to the present, with a good account of politics and production into the 1990s.

All and all this well organized and well written account brings real clarity to a relatively murky area of history. The book also contains detailed appendices estimating early emerald at Muzo, relative values of emerald and diamond in Europe in the 17th Century and an extensive bibliography. The author has uncovered several original accounts that have until now been unrecognized. Highly recommended.

Online Gem Evaluation; Slouching Toward Disaster, Part III

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by Richard W. Wise, G.G.

You Just Can’t Hide Those Lying Eyes:

Image A: Before photoshop, this is the image the camera saw. Photo Courtesy Precision Gem

In my first post on this subject, I made the point that making a purchasing decision or merely comparing prices by comparing images is fraught with difficulty. Photoshop and other similar programs are a good part of the reason why. The two images to the left illustrate the point. Image A is a custom cut Mali garnet. Based on the image, the stone appears to be a slightly greenish (10% yellow light toned garnet of medium saturation, not bright but not overly dull with a slight gray mask.

In Image B of the same stone, the original image has been altered by a simple tweak of the Saturation Enhancement Tool in Photoshop. The green secondary hue now appears more prominent, perhaps 15-20%. The big change, however is in the level of saturation. The color must now be described as vivid effectively doubling the value of the stone. The only hint that this is the same image is that the background in image A is slightly cooler (grayer) than the background in image B. However, if the photographer simply took two shots under the same lighting he could easily disguise that fact. Backgrounds can also be removed or replaced with a uniform black. Assuming that these two images appeared at similar prices on separate websites, an online bargain hunter would wrongly conclude that the owner of the stone labeled image B was offering his goods at a much more favorable price.

Approaching the Pinnacle of Perfection, Small bumps in Quality Equal Big Bumps in Price.

In low quality commercial grade gemstones, small differences is quality will not make a great difference in price. However, as quality nears theoretical perfection the importance of smaller differences is magnified. In the stratosphere of gemstone quality, small differences can make for very large price differentials. Lets take an example that everyone knows, the D flawless diamond. I chose this example because diamonds are very precisely graded using an internationally accepted grading system. According to The Guide a well respected industry publication, the current wholesale price of a 1.00 carat D-IF is 31% higher than the very next color grade, E-IF, compared by clarity grade, (D-Fl vs D-VVS1) the spread is slightly less, about 29%. A similar comparison between diamonds with a color grade of L and O shows only a few hundred dollars separating the two grades. These differences will not show up in an online image.

In colored gemstones these same percentages apply and the grading equation becomes much more complex. Colorless diamonds are graded based on slight tonal variations of yellow. Color, any color, breaks down into two additional factors, hue and saturation which must be added to tone in the quality equation. In nature there are few pure hues. The hue of a gemstone is composed of primary, secondary and sometimes tertiary components, a top color ruby for example, may be 75% red, 15% purple and 10% orange. A blue sapphire with 10% (or less) green secondary hue which will likely not be visible in an online image will sell at a dramatically lower price than a stone with a pure or slightly purplish blue hue. Similarly, an emerald that is 75% green with a 10-15% secondary blue hue can sell for double the price of a slightly yellowish stone. These slight differences in hue do not show up even in professional images. This makes online comparison between two images very deceptive and of little or no value.

Image B: The same gemstone after a tweak of the Saturation Enhancement tool in Photoshop

The Value of Images:

Online images are of some value. As a professional, I never use images to determine which stones I will buy though sometimes they can identify a stone that I will not buy. It is usually possible to tell something about the clarity and cut of a given gem by viewing the image. Both come with caveats.

Online Images are Many Times the Size of The Stone; so are the inclusions:

The Mali garnet at left weighs approximately one carat. That means the stone is somewhere in the range of 6 mm in diameter. The image shown is 38mm, 6.33 times larger. Many gems that are eye-flawless will appear visibly included (flawed). In colored gemstones, the eye standard replaces the loupe standard, what the eye sees is what is important, magnification doesn’t effect price. In most varieties of colored gemstones, the difference between eye-clean and visibly included is dramatic. It is similar to the difference between a diamond graded flawless and another graded SI2.

In some cases the image will actually distort what the eye sees. Award winning gem photographer, Robert Weldon, makes the point that due to the limits of depth of field, the camera’s lens will compress inclusions into a single plane increasing the prominence of the inclusions in the image. This compression can lead to particular difficulties when trying to accurately render images of expensive type II and III gemstones such as emerald where the difference in value between an eye-clean gem and one with eye visible inclusions will be dramatic. Online images are normally in j.peg format. This format is created, Weldon points out, by subtracting information in the original high resolution image.

Images can be useful in evaluating cut but bear in mind that the visual performance in a gem depends upon lighting. A well lighted gemstone may appear to perform better than one that is less well lit. The lighting environment is not visible, multiple light sources of the type normally used in photography can mask real deficiencies in cut.

Color and Lighting:

In the good old days, there were two types of light; the sun and light from a natural flame, a fire or a candle. This, as I point out elsewhere, is the source of the legendary “ruby red” alexandrite. When that gem was discovered in the mid nineteenth century, incandescent light was supplied by a candle and candlelight is distinctly reddish—after the invention of the light bulb, the ruby red alexandrite became distinctly purple because that light source is yellowish. With today’s technology, it is possible to virtually cherry pick a lighting environment that is strong in a given color. You can light sapphires with blue light, rubies with red. Again the light source is not visible—so how would you know until your gem arrives in the mail.

Online Gem Evaluation or Slouching Toward Disaster:

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by Richard W. Wise, G.G.,

author: Secrets Of The Gem Trade.

With the commercialization of the internet we have entered a new era for collectors of all stripes. Whether you are interested in antiquarian books or colored gemstones there is a great deal of information available and the opportunity to compare prices for the best deal.

If you are buying a commodity and I define commodities as items of uniform quality that are produced in multiples, comparisons are straight forward. Deciding between two new copies of the latest Jacky Collins romance novel is simply a question of price though you have to watch the shipping charge.

When it comes to collectibles, such as old coins where condition is a primary determinant of price, the buying decision becomes a bit more difficult. Two identical 1870 U. S. ten dollar gold pieces will vary dramatically depending upon condition.

Purchasing gemstones is much more complicated. First, no two gems are alike. Even colorless round brilliant cut diamonds that are traded with “certificates” that grade each of the four C’s vary in the relative percentages of brilliance, dispersion and scintillation. Even the so-called “ideal cuts” will vary markedly because the definition of what constitutes ideal varies from lab to lab.

Colored gemstones present an even broader set of variables and presents an almost insurmountable barrier to effective online comparison. In gemstones, color is the most important determinant of value and sub-divides into three factors, or values; hue, saturation and tone. Accurate grading of a gemstone depends upon two factors; the lighting that the gem is viewed in and the viewer. Change either and you no longer have consistent or accurate grading.

Online Color Comparison; The Impossible Dream:

The rise of internet forums has lead to the dubious practice of online grading by pixel. A neophyte gem buyer will post an image of a prospective purchase with a plea to the forum members to basically appraise the gem and by comparing quality with the purchase price, determine if said newby is getting a good deal. Unfortunately a number of forum members, many of whom ought to know better, jump in and tender their opinions. Though many online grading gurus would disagree, this sort of color comparison is nearly impossible.

There are a host of variables each of which will fundamentally alter the color that you think, you see. The image itself was taken by a specific camera in a specific lighting environment. Each make and model of camera has specific pluses and minus when it comes to accurately rendering color. Some are good with greens, some with blues others with reds. The color temperature of the specific lighting will make a big difference is the color you see. Natural light is reddish at dawn, turns yellow in the late morning, is neutral white at noon then turns bluish in the afternoon and finally reddish again at sunset. Artificial light can be controlled to emit almost any hue all of which affect the apparent color of gemstones.

Apparent color can also be altered by easily altered by editing software. Photoshop, the world’s most popular color editing software employs sophisticated tools that can easily alter the hue/saturation/tone of an image. With five minutes of training, the most unsophisticated Photoshop user can be taught to turn a ruby into an amethyst or even turn it green as an emerald. Though I have seen some forum gurus claim to be able to detect images that have been altered, such claims are pure nonsense.

Now we get to the monitors. Each monitor is different. 24 bit monitors differ markedly from 16 bits and from manufacturer to manufacturer and even day to day. Jennifer Robbins author of Learning Web Design tells her readers: “Let go of precise color control. Yes, once again, the best practice is to acknowledge that the colors you pick won’t look the same to everyone, and live with it. Precise color is not a priority in this medium where the colors you see can change based on the platform, monitor bit-depth, or even the angle of the laptop screen.”

No Computer Monitor on Earth…

$On one popular forum this spessartite garnet, offered by a Thai vendor, was said to show brown. Anyone with experience photographing this gem variety knows that the camera will often show brown where there is none. A result of off axis refraction.$

On one popular forum this spessartite garnet, offered by a Thai vendor, was said be brown or brownish. Though all my monitor shows is deep orange, those with experience photographing this gem variety know that the camera will often show brown where none exists. This is a result of lighting and off axis refraction.

The problem in accepting Ms. Robbin’s advise is that precise color is a priority nay a necessity in color grading gemstones. The Colorscan grading system pioneered by C. R. Beasley, founder of American Gemological Laboratories (AGL), the only U. S. lab that quality grades colored stones uses 36 different hue/tone combinations together with two degrees of gray masks yielding 108 different colors each associated with a specific quality level and therefore price, in blue sapphire. No color monitor on earth, even if properly calibrated can render all these combinations. The current director, Gemologist Christopher Smith, uses sample gemstones for stone to stone comparisons, he says he has literally hundreds of sample stones.

Viewed face-up, a gemstone is a mosaic of color, it is a complex scene. A static image captures but one aspect of a gem under a specific lighting environment. Many factors will effect the image you see. Lighting, viewing angle, lens and angles of refraction. The images shown here illustrate some of the problems.

I’ve chosen to discuss brown in orange gemstones because brown is dark toned orange. This means that the color you see is particularly vulnerable to misinterpretation. The gemstone acts a a prism, bending and bouncing light about like a demented pinball. If the light ray refracts at an angle from the perpendicular, off axis, the hue will appear darker, if totally away from the eye, black.

This professionally taken image of a 3.29 carat Nigerian spessartite from my inventory is almost identical in color (hue/saturation/tone) with the 7.46 carat stone at left yet it appears on my monitor as distinctly more orange and 15% darker in tone. Photo: Jeff Scovil

This 7.46 carat spessartite shows visible brown. It is from my own inventory so I can state with certainty that the stone itself has absolutely no brown.

In the image, this 7.46 carat spessartite shows a distinct visible brown. It is from my own inventory so I can state with certainty that the stone is a rich, vivid pure orange with absolutely no brown secondary hue or mask. On my monitor, the stone the image appears distinctly yellowish with brownish scintillation. Compare to the image of the 3.29 carat stone at right. Photo: Jeff Scovil

The Nuances of Grading:

Few jewelers and fewer collectors ever have the opportunity to see the complete range of quality possible in any given gem variety, be it sapphire, ruby, emerald or spessartite. Without that overview a grader lacks context. As the quality of a given gem approaches perfection, the beauty and rarity and therefore the price of a gemstone will increase dramatically. In the next post I will discuss the subtle nuances of grading that define those gems that are truly transcendent. Stay Tuned or sign up. You can receive GemWise by email or RSS feed, don’t miss another gonzo post, look along the right side and sign up ! I don’t guarantee that you will always agree but I promise it will never be boring. Comments welcome!

Investing in Gemstones, Part II; A Strategy:

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Avoiding the Con:

There were a number of phony gemstone investment schemes in operation during the hard asset investment craze of the late 1970s and early 1980s. Until Congress put a stop to it, investors were purchasing, gems, antiques and Shaker rocking chairs as part of their IRA portfolios.

To avoid prosecution many gem investment scammers set up boiler room operations in Canada, but sold mostly to gullible U. S. investors. The pitch was simple and ingenious. To keep buyers from seeking an outside appraisal, the gems arrived in sealed packets with a microfilmed “certificate of authenticity”. Buyers were warned that breaking the seal would invalidate the certificate and negate affect potential resale.

Over the years, several victims have sought me out to appraise their purchases. In all cases, the gems were wildly overpriced stones and of a quality best described as Continue reading →

Gem Prices follow Real Estate in the New Gilded Age

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Gem Prices in The New Gilded Age

By Richard W. Wise, G.G.

Gem prices are definitely on the rise. However, these price increases seem to be following general market trends that is, the largest price increasing have been at the very upper end of the market while commercial qualities have remained more or less static. This compares almost exactly to the situation in the U. S. real-estate market.

From Florida’s Miami Beach to The Berkshires of Massachusetts, homes in the under 1 million price range are languishing on the market while homes priced in the one million plus category find ready buyers. In a recent article the New York Times it is reported that condos priced at a median price of 1 million in the Miami area have slipped slightly while those at the 1.5 million level have actually seen a slight increase. In the upscale Berkshire Mountains of Massachusetts the story repeats itself. Prices on single family homes below 1 million are not selling while the market for 1 million plus homes is described as brisk.

Likewise, Prices for fine quality Black opal have doubled in three years and prices for ruby, particularly the very rare fine unheated stones has risen 60%. Due to a diversity of sources, prices for unenhanced fine blue sapphire, the most popular colored gemstone in the U. S. is up a paltry 20%.

Some of this increase is due to the weak dollar which is down 40% against the Australian dollar, 20% against the baht and 22% against the Columbian peso. This has made U. S. real estate relatively cheap for foreign buyers. Since the international gem market operates mainly in dollars the effect has been similar.

As we move toward the low-end, gem prices have hardly moved at all. The bread and butter market is in the doldrums, commercial to good qualities have hardly moved upward at all. In fact, the entire low to mid range jewelry industry is experiencing something of a recession.

I Get Letters:

Seems like I get at least one question like this every week:

Judy from Melbourne writes:

Hello,

Thank you for your site and all your wonderful articles and books.
I wonder if you can help with how to appraise a very unusual stone my partner is thinking of buying. It is a 66ct peridot, loupe clean, square step cut with a deep pavilion, very dark green (but not olive) with almost no yellow, evenly saturated, and bought in Burma from the Burmese owner of a small mine.

The price being asked is around…(removed)…Appraisers here in Melbourne have never seen a similar stone, and say they have no benchmark for it, but it has been suggested that collectors might pay substantially more than the price being asked.

I would very much appreciate any guidance you can give me.

Answer:

Like Antiques Road Show in braille.

Judi,

How does one answer such a question without seeing the stone. I get quite a few similar emails so, if you don’t mind I will post the question and answer on my blog. This reminds me of a call in program occasionally run on our local radio station, WAMC. Two antique dealers are asked to value items described by the callers. They never actually see the item but that fact does not seem to get in their way. Its like Antiques Road Show in braille.

One of a kind stones, big stones are difficult to appraise even when they are in front of you. Is there a peridot worth that price, certainly! Based on a respected price list, the top retail price for Peridot in that size would be $360 per carat. for an extra fine gem. Is your stone worth that much? I really have no idea. The best one I ever saw had an asking price of $5,000 per carat. You say its not olive meaning no gray mask? The depth of color (saturation, tone, crystal and the quality of the cut would be the remaining key factors.

My best advise: Show it to someone who knows. In lieu of that, its anybody’s guess

Whats a buyer to do?

Follow me on gem buying adventures in the pearl farms of Tahiti. Visit the gem fields of Australia and Brazil. 120 carefully selected photographs showing examples of the highest quality gems to< img style="margin: 0pt 10px 10px 0pt; float: left; cursor: pointer;" src="http://3.bp.blogspot.com/_jPHBjO2OLDs/RjD1BsdOzzI/AAAAAAAAALU/cJrRFFng7C8/s400/Front+cover++3-D+art.jpg" alt="" id="BLOGGER_PHOTO_ID_5057811790999506738" border="0" /> educate the eye, including the Rockefeller Sapphire and many more of the world’s most famous gems. Consider my book: Secrets Of The Gem Trade, The Connoisseur’s Guide To Precious Gemstones.

“Wise is a renowned author… He’s
done a marvelous job of this first book, monumental work, a tour de force…My recommendation: Buy this book”.

Charles Lewton-Brain, Orchid

whether you like to know what the best colour is in Tanzanite, or how to grade a Diamond, you will find it in this book. No other book I read before dealt with this topic is such detail as Richard Wise’s masterpiece.”

A. Van Acker, FGA
Amazon June 2005

“Secrets Of The Gem Trade: The Connoisseurs Guide To Precious Gemstones by Richard W. Wise is an impressive new reference for dedicated dealers and collectors of gems, gemstones, and … pearls. Introducing and descriptively exploring each and every gem covered in the easy-to-use reference, Secrets Of The Gem Trade contains an illustrated summary of each stone inclusive of its history and general information, hue and tone, saturation, which may be noticed as the finest, an understanding of the particular gems rarity, and the caution for synthetics and how to depict them, however depending upon the stone there may be description of clarity, color fading, multi-color effect, etc. Secrets Of The Gem Trade is very highly recommended to anyone interested in gemology as a superbly organized, authoritative, comprehensive, and easy-to-follow reference.”

Midwest Book Review
April 2006

Only $37.95. Read a couple of chapters online: www.secretsofthegemtrade.com.

Buy it on Amazon: www.amazon.com

Color Change/Color Shift

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Grading The Colorful

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Grading the Colorful, The Rocky Road to Quality Assessment

by Richard W. Wise, G.G.

“Collectors Universe has stated it has every intention of becoming the world’s leading purveyor of diamond and colored stone pedigrees—”maybe not tomorrow, or next year,” (CU President) Haynes says, “but within the foreseeable future.”

David Federman, Professional Jeweler, 2006

At the beginning of a new year it is traditional to assess the past year, make resolutions and talk about the future. Several happenings over the past twelve months that considered in isolation are important taken as a whole appear to be crucial milestones along the road toward colored gemstone quality grading.

A consortium of seven major gem laboratories under the aegis of the Laboratory Manual Harmonization Committee (LMHC) established important precedents:

First, they abandoned the traditional protocol of naming a gem based on species and variety. The committee agreed that on grading reports issued by member labs to use the term “Paraiba” to describe all copper colored or cuprian tourmalines regardless of their actual source.

In a separate decision, the LMHC also decided to stray beyond the realm of verifiable science and enter the world of aesthetics. They agreed to adopt a set of color parameters for and use the term “Padparadscha” sapphire on grading reports issued by member labs.

This year a new player entered the grading games: Collectors Universe (CU), a publicly traded company that provides certification for coins stamps and guess what, baseball cards purchased American Gemological Laboratories (AGL) the only major U. S. lab that issues quality grading reports on colored gemstones. CU has the financial muscle and appears poised for an strategic play: The company already owns Gem Certification and Assurance Lab (GCAL) as well as Gemprint, the diamond identification and registration system that will laser print an ID # on gemstones.

In order to have a universal colored stone grading system you must have a universally acceptable methodology. Internet shoppers, in particular, are demanding a way to compare apples to apples and what the market requires the market sooner of later gets. Getting all major players to accept a single methodology may be difficult but a broad basis of agreement between a number of important labs may do the trick. The LMHC includes seven of the world’s most respected gemological laboratories: (AGTA Gem Testing Center, CISGEM (Milan), GAAJ (Japan), GIA (USA), Gemological Institute of Thailand, Gübelin Gem Lab (Switzerland) and SSEF Swiss Gemmological Institute (Switzerland) missing only AGL and The Swiss Lab Bangkok (GRS) the very well respected Bangkok based lab run by Adolph Piretti.

Historically, no institution, not even the mighty Gemological Institute of America (GIA), the originator of the universally accepted diamond grading system, has succeeded in creating an acceptable colored stone grading system. GIA tried twice, first in the 80s Colormaster, a sort of color blender and then with Gemset, a set of round faceted plastic doohickeys, both of which were flawed and failed to win industry wide acceptance. GIA has wisely abandoned its go it alone strategy and joined LMHC.

Instrument based color determination appears to be the wave of the future. According to American Gemological Laboratories C. R. “Cap” Beasley “instrument based measurement is simply more consistent”. The fact is; you have the rock, the light and the observer, standardize the latter two and you are eliminate two variables. Does Beasley have an instrument? None that he will admit to.

AGL is still the only major laboratory that grades colored gemstones. Beasley introduced his own system, Colorscan, in the early 1980s, a system that many gemologists including this writer believes was the most viable system yet created. Colorscan, however, relied on the human eye as observer. New Computer based systems such as Gem-e-Square that project a range of hue/saturation/tone on a color computer monitor also require the human eye and judgment to make a call.

Collectors Universe appears to be making a bid to become a major player in quality grading. I will be interviewing CU president Bill Haynes, later in the week. Stay tuned.

Interested in reading more about real life adventures in the gem trade?

Follow me on gem buying adventures in the exotic entrepots of Burma and East Africa. Visit the gem fields of Austrailia and Brazil. 120 photographs including some of the world’s most famous gems. Consider my book: Secrets Of The Gem Trade, The Connoisseur’s Guide To Precious Gemstones. Now only $26.95. You can read a couple of chapters and order online: www.secretsofthegemtrade.com

Do ya feel lucky? Win A Free Copy:

Thats right win a free copy of Secrets Of The Gem Trade, The Connoisseur’s Guide To Precious Gemstones, answer the question.

The Hope Diamond, Inflation in the Seventeenth Century

In 1669 Louis XIV of France purchased the French Blue diamond from the famous gem merchant Jean-Baptiste Tavernier for 220,000 livres or 42.7 million dollars (1 livre = $1,941.). In an inventory taken by the French crown in 1691 the Sancy Diamond, a colorless stone of 55.23 carats and the largest white diamond in Europe at that time, was valued at 24.2 million dollars.

By the time this inventory was taken, The French Blue, had been recut by M. Pitau to 69 carats, a 40% loss in weight. Despite this the stone that ultimately became the Hope Diamond, was valued at…in 1691? The first person who comes closest wins a signed paperback copy of Secrets Of The Gem Trade. Post your answer in French livres and your email address to the Comments section of the blog. Winner’s name to be posted on GemWise in two weeks. Hint: read Ronald, The Sancy Blood Diamond, Morel, The French Crown Jewels

Of Tilt-Windows, Off-center culets and other minor issues:

Grading; From Minus To Plus:

Each Gem Is an Individual with a distinct personality and should be judged on its merits:

A Non-Issue:

A Little Extinction Contributes To A Gem’s Beauty

Extinction As A Fault:

Ease of Use:

Nomenclature Issues:

Pricing Accuracy:

Overall Evaluation:

New Technologies May Require Changes is How We Look At Gems:

The Tea Party To the Rescue:

Book Review: The Colour of Paradise, The Emerald In The Age of Gunpowder Empires

You Just Can’t Hide Those Lying Eyes:

Approaching the Pinnacle of Perfection, Small bumps in Quality Equal Big Bumps in Price.

Image B: The same gemstone after a tweak of the Saturation Enhancement tool in Photoshop The Value of Images:

Online Images are Many Times the Size of The Stone; so are the inclusions:

Color and Lighting:

Online Color Comparison; The Impossible Dream:

No Computer Monitor on Earth…

The Nuances of Grading:

Image B: The same gemstone after a tweak of the Saturation Enhancement tool in Photoshop

The Value of Images: