Category Archives: collecting gems

Colored Diamonds; Really The Blues Part II

by Richard W. Wise, G.G.

Fancy diamonds are back in the news, another auction record broken This time its blues. At Bonhams of London, a 5.30-carat fancy deep-blue diamond set a world auction record for price per carat when it sold for approximately $7.3 million, or $1.8 million per carat bettering the previous record of 1.68 million per carat. I recall a 5+ carat Fancy Deep blue emerald cut I viewed at the Las Vegas show some five years ago with an askiing price of 1 million per carat, quite a nice appreciation.

Some might argue that auction prices do not reflect actual market prices, but in the case of fancy colored diamonds and colored gems such as important ruby and sapphire, auction prices set the market. This is a pattern that began to emerge in the 1990s and accelerated in the early 2000s as retail buyers became a larger factor in the auction market. Online auctions also have helped spread the word about important gem sales and in many cases, auction prices actually lead the way.

Update on The Wittelsbach:

Another famous blue diamond is The Wittelsbach, the largest blue diamond ever sold at auction. I wrote about this gem previously, After being recut and regraded from Fancy Deep Grayish Blue to Fancy Deep Blue and exhibited at The Smithsonian Institution side by side with The Hope, London dealer Lawrence Graff reportedly sold the gem for $80,000,000 or something over 3.3 million per carat.

The Wittelsbach-Graff after recutting. Note the distinct grayish hue. Most published and Photoshopped images show the diamond as a rich pure medium hue, the reality is somewhat different; Photo: Gary Rossman

Of course there are a number of Fancy Deep Blue diamonds over five carats but no others over thirty excepting The Hope. Weighing in at 31.06 carats, The Wittelsbach commands a price based on the extreme rarity of a colored diamond of this size.

Buying Gems on The Internet; Picture Perfect

2 Replies

by Richard W. Wise, G.G.

Everyone is familiar with the old sayings; seeing is believing and a picture is worth a thousand words. In the internet age, however, I'd suggest prospective gem buyers embrace another old saying, "believe half of what you see!" Yes, thanks to Photoshop coupled with the ability to select a broad range of lighting options at varying color temperatures, a picture can tell a thousand lies. Despite this, gem buying on the internet has increased a thousand fold aided by a crop of gem forums where hobbyists, prospective grooms and gem collectors gather to share information and critique gems on offer.

Many of the participants in these forums believe that a gemstone is just another commodity that qualities are uniform and prices follow some sort of median so that if most of the 1 carat sapphires they see online are $3,000 a carat then any stone with a price tag above that number is, by definition, expensive and overpriced. As I have said in my book, Secrets of The Gem Trade, and other places, this is simply not true. The prospective buyer who limits himself to images and median prices is doubly mistaken assuming that quality is his goal. This myth is reinforced by largely untrained online gurus who claim the mystical power to judge the quality of a gemstone by simply evaluating an image and by consumers who simply want to believe them rather than doing some of the tedius work of actually comparing stones.

As gemstone approach theoretical perfection in color/cut/clarity and crystal, smaller differences in those criteria make for larger and larger differences in price. At the same time, those subtle difference are extremely difficult to capture in an online image. An image can tell a lot about a gemstone with regard to clarity and color, I can often see enough to pass on a given stone, however, I cannot see enough to make a firm buying decision. From this point on, actual comparison is absolutely essential.

Unrealistic Expectations:

Of Off center Culets and Tilt Windows:

Natural Heliodore, Golden Beryl from Connecticut

1 Reply

10986: 2.11 Carat pear shaped brilliant cut with exceptional vivid color and crystal.

by Richard W. Wise, G.G.

10987 A 1.74 Carat ovall brilliant heliodore from the Roebling/Merryall MIne, Litchchfield, Ct. The gem exhibets an exceptional vivid medium toned golden hue.

10987 A 1.74 Carat oval brilliant heliodore from the Roebling/Merryall Mine, Litchfield, Ct. The gem exhibits an exceptional vivid medium toned golden hue.

Golden Beryl; An American Gem

In the 19th Century, the state of Connecticut was known as a major source of golden Beryl.

In the past few years a fair amount of golden beryl a.k.a. heliodor has entered the gem market. Material currently in the market is coming from Pakistan, Brazil and Ukraine and although there is no reliable gemological test that will prove irradiation, much of this material is thought to be enhanced by gamma radiation, a method that leaves behind no footprints. Of late there have been misguided attempts to cash in on the gem's more famous sibling by re-labeling the gem as "yellow emerald."

The continental United States is not known for its gem wealth though historically both California and especially the New England states have produced some exceptional gems. In the 19th Century, Maine was known as a repository of gem quality tourmaline, some beryl and amethyst. Most of the gems found in New England are of pegmatic origin the result of long super-hot magmatic fingers working their way up through cracks into the country rock causing localized melting into a chemical stew and its constituents, where beryllium oxide was present, might reform into beryl crystals. Many of the most important strikes were found in Maine including the famous Mt. Mica Mine which resumed operations in 1990 after a long hiatus. Pegmatites are found in all the New England states excluding Rhode Island and are particularly numerous in Maine and New Hampshire. Gem mining was in most cases simply a byproduct. The mines were mainly exploiting mica, Beryllium and feldspar.

Beryl is a family name whose best known offspring are emerald and aquamarine. If a beryl is pink it is known as morganite if red it is called bixbite or simply red beryl. In the 19th Century, golden beryl was quite rare and Connecticut was considered a major source. The term heliodore, from the Greek meaning "gift of the sun" was originally a trade name made up to describe yellow beryl from Southwest Africa.

"A Gift from the Sun," Gem Mining in Connecticut:

Few realize that the George Roebling or Merryall Mine located in Litchfield County, Connecticut was, historically, one of the most productive and commercially important gem mines in the United States. This mine opened in 1880 as a feldspar and mica mine and worked intermittently until 1955 when it was closed. According to the late John Sinkankas, Merryall is known to have produced particularly fine beryl in shades of blue, yellow and green including a 40.44 blue-green heart shaped gem that now resides in the Smithsonian. The mine produced some sizable aquamarine, but most of the heliodore production was limited to very small faceted gemstones.

We recently acquired a few particularly fine rough examples of natural unenhanced heliodore, portions of a single large crystal, sourced at the Roebling/Merryall Mine site from a pile of unsorted mine run material in the early 1980s. The crystal was inside a large boulder. This material has been precision cut into a few lovely heliodore gems. These gems are flawless to the eye, exhibit a particularly fine crystal structure, a high degree of transparency and a vivid pure yellow hue and perfectly cut by our lapidary.

10987 Rough material from which the 1.74 carat oval, 10987, was cut.

10987 Rough material from which the 1.74 carat oval featured at the beginning of this post, 10987, was cut.

As Sinkankas points out, very little of the material sourced from this location is of gem quality never mind eye-flawless material. Mine run material containing 1% Beryllium is considered a rich deposit. Gems from this site have not been on the market in many years. For the gem collector, this is an or for the jewelry lover looking for a lovely vivid yellow gemstone, this is an opportunity to buy American and acquire a particularly fine gem from a truly rare source.

Gemstone Cut Grading; Distinctions Without a Difference II

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

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

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.

Kashmir Sapphire, Another Auction Record

14 Replies

Dateline: Hong Kong

Current world record holder, 26.41 Carat Kashmir Sapphire Courtesy: Christie's

A New World’s Record:

November 29th, Christie’s Auction House, Hong Kong, sold a 26.41 carat Kashmir sapphire for 3,838,508 or $145,342.00 per carat. This sale establishes a new world’s record price of Kashmir sapphires sold at auction, besting the former world’s record also established at Christie’s (New York) for the 22.66 carat Hill Sapphire which sold in April 2007 for $3,064,000 or $135.216.00 per carat.

Kashmir sapphires were originally found on a small hillock 13,000 feet up in the mountains of the now disputed Indian state of Kashmir in 1881-1882. The harsh conditions at this altitude meant that the mines could only be worked about one month per year. By 1887 the output of the mines had diminished substantially. The original lessee abandoned the diggings in 1905. Four other groups had a go at it with little success and the sites were more or less abandoned in 1928. A bit of material is still occasionally found, alluvial material at the bottom of the ridge, but the major production of Kashmir sapphire lasted a mere six years.

Kashmir stones are highly esteemed for their color, a vivid purplish blue, a hue often described as “cornflower blue.” Others, most notably Richard W. Hughes, author of the seminal book Ruby and Sapphire, describe the finest color as a Pepto Bismol bottle blue. The problem with this characterization is that Pepto Bismol bottles are now pink—but there are those of us who are old enough to recall when the bottles were a bright medium blue. I recall seeing only one stone of this description and it hailed from Sri Lanka.

Kashmir’s famous characteristic, however, is the silky, milky or fuzzy texture that somewhat diminishes the diaphanity (crystal) of the stone. Myriads of tiny inclusions that resemble dust caught in a ray of sunlight or a sub-microscopic milky way, will, when present, diffract and refract the light, causing the stone to take on a velvety glow. Similar inclusions are sometimes found in gems from Madagascar and Sri Lanka, but absent geographical certainty, these “Kashmir type” sapphires do not command nearly the price of those with old mine provenance. The current record holder was accompanied by four laboratory reports certifying Kashmir origin. This, of course, begs the question: If gems are all about beauty and sapphires from other locations have all the characteristics of the finest Kashmir, why does anyone care where the stone is from? The short answer is branding. The market recognizes a value in stones from the original mine. It is also fair to say that although stones can be found with the characteristic glow, very, very few approach the pinnacle of Kashmir color. I have only seen two stones that can be described as #1 Kashmir color and both were from the old mine.

What a difference a light makes, record breaking sapphire before re-cut, note the large culet visible through the table. Photo courtesy Stone Group Labs.

What a difference a light makes; the current record holder before a re-cut shaved a single carat. Note the large culet visible through the table and the characteristically velvety texture or crystal. Photo courtesy Stone Group Labs.

Rapidly Escalating Prices:

Kashmir prices have been increasing steadily since the late 1980s. According to connoisseur and author Benjamin Zucker, a twenty carat fine quality Kashmir sapphire was worth $25,000 per carat in 1976, though I recall an exceptional stone that sold at auction in the early 1980s for $12,500 per carat. By the turn of the last century prices for extra-fine examples at auction passed $100,000 per carat. Pricing must be taken with a grain of salt. Given varying qualities, the vicissitudes of auction houses, and the lack of any real standardized grading system, it is difficult to compare stone to stone.

Prices for premium gemstones, fancy color diamonds, type IIa colorless diamonds, ruby, sapphire, emerald and lately spinel, have all increased markedly since the 2008 bust. This can be traced to a lack of confidence in paper currencies, generally, and the dollar and Euro in particular.

Connoisseurship–Opinions Vary:

Bear Williams of Stone Group Labs, the first gem laboratory to evaluate the new record holder, was impressed. “My hair kinda stood up on end, it had some sort of magic,” he said describing his first look at the sapphire. When Williams saw it, the stone weighed over 27 carats before it was re-cut slightly and re-polished. From all indications the stone is quite superior to the Hill Sapphire, which American Gem Labs President Christopher Smith described as a “nice stone.” in 2007. Smith rated the former record holder, the Hill Sapphire, at an 8-8.5 on a 1-10 scale. Williams puts this new one well into the 9s, “maybe a 9.8” he says. Chris Smith at American Gem Labs, who did a full quality evaluation, gives the stone an overall Total Quality Integration Rating (TQIR) of Exceptional and a color grade of 2.5 (1-10 scale). Note that AGL’s TQIR factors in rarity, together with quality factors. A five carat Kashmir or the same quality would be graded Excellent.

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

6 Replies

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

12 Replies

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.

Grading Tanzanite; In Praise of Purple

10 Replies

Gem quality tanzanite showing both its primary blue (left) and secondary purple (right) hues. Wise, Richard W., Secrets Of The Gem Trade, p.219

by Richard W. Wise, G.G.

“Roses are red violets are blue but tanzanite ain’t violet.”

In 2007 The Tanzanite Foundation came out with a “standardized” grading system for tanzanite. Shortly later, The American Gem Trade Association’s laboratory adapted this grading system for use on its grading reports. All tanzanite would henceforth be graded on a color scale from violetish blue (vB) to bluish violet ( bV). Great idea, only one problem, they got the colors wrong, they missed purple.

Tanzanite’s primary hue is often blue but never a pure blue. Tanzanite exhibits a secondary hue which is always present. The secondary hue ranges from violet to purple, which though often confused in common speech are distinctly and definably different hues. Violet is a primary spectral hue that lies halfway between purple and blue and Purple is a secondary or modified spectral hue meaning that it results from a mixture of two primary spectral hues (red and blue). That explains why it doesn’t show up when you view the rainbow. Purple is positioned halfway between blue and red. The confusion of violet and purple is not new it goes a long way back but lets begin with Newton. Sir Isac is rightly given credit for initial work in color theory— published in 1706, his was the first color wheel.

The original color wheel courtesy of Sir Isac Newton. In 1708 a Frenchman, Claude Boutet (Traité de la peinture en mignature) added purple.

If you squint (image right) you will see that Newton identified indigo and violet as the two hues existing between blue and red. He either forgot purple or was perhaps pre-purple. Prior to the movement to standardize nomenclature in the 18th Century, colour names, like spelling, were not standardized. Tavernier, for example described the great blue diamond that he sold to Louis XIV as “violet.”

What isn’t generally understood as that Newton’s color wheel was all about opaque colors. Colored light adds a whole new dimension to the color equation.

Using oil paints, mix equal amounts of the two opaque colors red and blue together and the color you get is magenta. Purple can be mixed but painters are reluctant to use the term, preferring blue-violet instead, further adding to the confusion.

“Roses are red, violets are purple sugar is sweet and so is maple surple”

Roger Miller

Change from opaque media to to colored light you dramatically change the result. Mix equal amounts of red and blue light together and you get, guess what, purple.

After tanzanite has been heated, and virtually all tanzanite is heat treated, it is dichroic. That means that light entering the gem crystal divides into two rays each containing a portion of the visible spectrum. The dichroic colors of tanzanite are red and blue—the red is often reddish purple. If the gem is properly oriented before cutting, the face up color will mix the two yielding a range of hues from violetish blue (vB), to purplish blue (pB), to purple-blue (PB) to bluish purple (bP).

Where is the Lab Harmonizing Committee When You Really Need Them?

Studies show that it is particularly difficult for the human eye to distinguish purple, particularly at light tonal levels. This is known as the Bezold-Brücke effect. When purple is present in light-toned gems, the eye wants to see blue. In fact at light tones and low levels of saturation it is difficult to separate purple from violet or even pink. This occurs a lot in light toned topaz. Dealers will often categorize light purple as pink topaz. At darker tonal levels the eye is not bothered by the Bezold-Brücke effect. Yes tanzanite can often be violetish, even blue-violet, but finer stones are purplish-blue so how can purple be left out of the definition?

Traditionally tanzanite has been graded by what I call the “look-alike” standard. When the stone was first discovered, Harry Platt, the Vice President of Tiffanys compared it to sapphire. Platt declared that the finest color of tanzanite was a pure sapphire blue, which means that the finest tanzanite, like sapphire is a medium dark tone (75-80%) slightly violet to purplish blue. A medium dark toned true blue barely exists in nature and only in tanzanite when viewed in noon daylight or daylight fluorescent lighting. Put a “pure” blue tanzanite under the light bulb and a distinct violet to purple secondary hue will always be visible. In the finest stones, a medium dark toned purple adds a velvety richness to the blue, so beautiful that even the folks all the way over at the Tanzanite Foundation, at AGTA and even at GIA should be able to see it.

Update on The Wittelsbach:

Unrealistic Expectations:

Of Off center Culets and Tilt Windows:

Golden Beryl; An American Gem

In the 19th Century, the state of Connecticut was known as a major source of golden Beryl.

"A Gift from the Sun," Gem Mining in Connecticut:

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:

A New World’s Record:

Rapidly Escalating Prices:

Connoisseurship–Opinions Vary:

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:

Where is the Lab Harmonizing Committee When You Really Need Them?

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

The Value of Images: