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The Buyers’ Guide to Noble Stones

Like gold and diamonds, colored stones are magically compelling, prized for their beauty and treasured as stores of value for millennia.  The vivid tones, sparkle, and rarity of rubies, sapphires and emeralds have made them the subject of mythologies and divinity stories in every culture that has had access to them. They are increasingly regarded as artworks of Nature.

Lab Reports Improve Gem Market’s Transparency

Detail of Shah Jahan on a Terrace. Painting by Chitarman, c. 1627-8. The Metropolitan Museum of Art

Historically, colored stones were an irresistible but dangerous area of collecting. Imitations, simulations and treatments are as old as the love of gems, and can be difficult to detect.The eighteenth century Mogul Emperor Shah Jahan, a studious gem collector, deliberated carefully before making purchases, once bringing an important ruby into a prison for an expert consult - this expert was the Shah’s own deposed father, whose judgment he still found indispensable. But before modern instrumentation, no system for detecting fraud in this high value asset class was foolproof.

Thankfully, gemology is now a modern laboratory science. Armed with analytical laboratory reports, called “certs” by the trade, buyers can be sure that their ruby, sapphire or emerald is natural and free from the sophisticated treatments used to doctor the color and clarity of inferior stones. Additionally, with geographic origin reports, the laboratories help buyers can select confidently from a variety of gem producing areas that have appeal for their historical importance and for their typical range of hues and tones.

Geography Matters

Geography affects the characteristics of colored stones because, unlike diamonds, they form in diverse areas of the earth’s crust, under distinct geological conditions. During the dynamic process of mountain building, gem crystals form over millions of years, stopping and starting again, growing amidst a variety of elements and minerals that affect their color and inclusions. Gems whose characteristics fall within the traditionally prized range of color identified with a particular deposit can receive a special designation on their laboratory “certs”, such as “Classic Burma”, “Classic Kashmir” or “Classic Colombia”, from American Gemological Laboratories. Many traditional mines in these regions have been largely depleted, with the best material often having been exploited first, a fact which enhances these gemstones' increasing rarity and desirability.  Overall, these significant historic deposits - including Burma, Kashmir, Colombia, and Sri Lanka (Ceylon) - have shaped global tastes powerfully over the centuries, creating longstanding value that will endure into the future.

Avoiding The Treated but “Natural” Gemstone Loophole:

Some buyers are unaware of the counterintuitive fact that, due to a loophole in the law,  treated and “enhanced” gemstones can be sold as “natural”. Untreated gemstones - stones that are truly natural - make up a tiny fraction of the colored stone market - less than 2%. Treatments include traditional heating, as well as fracture-filling with glass, beryllium infusion, and other high tech methods of making otherwise low-value stones simulate their naturally beautiful, untreated counterparts. However they may look, these treated stones are simply not comparable with natural, untreated gems, and serious collectors avoid them.

This truth is evident in the secondary market, where treated rubies, sapphires and emeralds - even those mounted by famous brands - re-sell for a small fraction of their original prices, and at a large discount to natural, untreated gems. Treated “natural” stones are a form of consumption rather than investment.

Science Protecting Collectors: The Gemological Laboratory Report

In the 20th century, pioneering Swiss and American gemological laboratories began analyzing gemstones. They follow and detect the latest treatment technologies in order to call out these enhanced stones. Further, for decades, these labs have been analyzing natural, untreated rubies, sapphires and emeralds of known geographic origin, building databases of their chemical characteristics and distinctive inclusions. They use a variety of scientific techniques, including microscopy and various forms of spectroscopy to map and measure the interior world of gemstones from different regions, identifying mineral inclusions and elemental impurities within the crystal structure that indicate the region of formation.

Long-standing laboratories led by highly experienced scientists have complied the most comprehensive sets of data, and produce the most sought-after treatment and region of origin reports. With their vast banks of data, these labs are best positioned to distinguish reliably among gems which may share some characteristics, due to their similar orogenic origins. Among the most trusted and well known colored stone labs are American Gemological Laboratories (AGL,1977), Swiss Gemological Institute (SSEF, 1972), GemResearch SwissLab (GRS, 1996) and Gübelin Gemological Laboratory (Gübelin, 1923).  

The World’s Most Sought-after Precious Stones:

Burma Ruby: 

Ruby crystal (1.7 cm × 1.7 cm × 0.5 cm) in marble from Bawpadan, Mogok, Myanmar. Photo: Louis-Dominique Bayle © le Règne Minéral

Historically, Burma was sequestered from the outside world for long periods, and its rulers imposed severe punishment on gem exportation. Rubies from this region bring the highest prices, with the exceedingly rare specimens weighing over 5 carats - the rarest of all colored stones - reaching more than a $1,000,000 per carat. “Pigeon’s blood red”, a centuries-old description of the finest ruby hue, is the color standard against which rubies are judged. Another quality of most Burma rubies is their formation in calcite host rock that is largely free from iron impurities. With less interference from iron, Burma ruby’s chromium atoms create red fluorescence in daylight, intensifying their color with a subtle glow. Fine Burma rubies range in hue from a pinkish red to deeper tones.  

Burma Sapphire:

Mining in Mogok, Burma: From 1600-1885: All rubies over a certain value belonged to the Burmese crown, on penalty of death “Sketches of the Upper Burmah by Lieutenant A. G. Marrable, 51st King's Own.”, The Illustrated London News, Volume 90, 1887

More plentiful, and occurring in larger sizes than Burma rubies, this gem is ideally “royal blue”, signifying a rich, saturated hue that is deep and well distributed. While also rare, Burma sapphires are more abundant than the rubies. Their supply has also been controlled by Burmese authorities over the centuries.

Kashmir Sapphire:

Accidentally discovered in the 1880s by a traveller passing through a high Himalayan pass, the Kashmir deposit yielded sapphires whose ideal specimens consistently display an intense yet soft and velvety blue under varied lighting conditions. Submicroscopic inclusions scatter light around these gems, diminishing less intensely colored zones and helping eliminate areas of dark “extinction” that result from the way light escapes even from ideally cut gems. Among sapphires, Kashmirs achieve the highest prices per carat. After the initial deposit was exhausted, a subsequent mining effort in the 1930s yielded deeper, darker crystals, and was abandoned. Yale professor Cap Beasley, founder of American Gemological Laboratories, visited the area of the Kashmir Mines in the 1980s. A disputed territory between India and Pakistan, patrolled by armed insurgents and snowbound for much of the year, the region is not currently viable for exploration. 

Sri Lanka/Ceylon Sapphire:

Adam’s Peak & Surrounding Region, Sri Lanka, 1954, Howard Sochurek, Life Magazine, © Time Inc.

Sapphires from Sri Lanka (Ceylon) come from the oldest significant global deposit of ruby and sapphire, which lies in a large region with plentiful gem gravels on the alluvial plains surrounding Sri Pada (known as Adam’s Peak). Attesting to the existence of early trade routes with the Middle East, Sri Lanka sapphires have been found in 5th century B.C. Egyptian tombs. These sapphires range in color and quality, from a pleasant watery blue to a highly saturated, soft hue that can approximate that of a fine Kashmir. The Sri Lanka deposit has also yielded large gem specimens over 400 carats, such as the Logan Sapphire held by the Smithsonian, as well as fine “star” stones. Cut en cabochon, with a domed top, these intriguing gems exhibit a 6-rayed star phenomenon.

The Logan Sapphire, a flawless crystal of 423 carats Sri Lanka/Ceylon sapphires more typically occur in larger crystals, with fewer inclusions Credit: Smithsonian Institution

Madagascar Ruby:

Also formed in the Indian Ocean orogenic zone that encompasses Sri Lanka and Burma, Madagascar rubies at their finest can display an intense hue that approximates the ideal “pigeon’s blood red” of Burma rubies.

Colombian Emerald

South American peoples mined emeralds from the first millennium A.D., collecting them and offering them to their gods. When the Spaniards conquered the Inca empire in the 16th century, they seized the gems, mines and means of production. Half way across the world, the gem connoisseurs of Mughal India, the wealthiest empire of the time, were the principal buyers of these stones, prizing them as them as the finest deposit they had ever seen, and treating them as sacred objects. 

View of the landscape of the Muzo area, from the family album of George Dixon, taken before 1890, with the handwritten comment reading: “A picturesque native bridge across stream. Road leading to Muzo mines.” Courtesy of Simon Hamilton.

Compared to other historic deposits like those of Egypt and Hungary, Colombian emeralds from the Muzo and Chivor regions, lying on opposite sides of the same mountain range, achieve the finest slightly bluish-greens. Emeralds form in highly unsettled geological environments. Therefore, during formation, they are generally more prone than sapphires and rubies to disturbances that affect the purity of the crystals. Remarkably, fine Colombian stones are relatively free of heavy inclusions in comparison to the other historic deposits. Oiling emeralds with natural materials such as balsam, sometimes colored, is a traditional method of smoothing the stones’ surface to enable a continuous pathway for light. Oiling is noted in laboratory reports, and is broadly acceptable to collectors. Also, Colombian emeralds are colored in part by the presence in the crystal structure of the element chromium, which results in a satiny, intense green that connoisseurs typically prefer to that of emeralds from the newer mines in Africa. Emeralds from Africa derive their coloration partly from iron, which can create a subtle brown toning. 

Collecting Tips:

Buy “certed” gems.

View rubies and sapphires under varied lighting conditions, at different times of day.

Exsolved rutile silk in Ceylon blue sapphire, Photo: Wimon Manorotkul, 2014

Color in rubies and sapphires varies throughout the day depending on the changing concentration of wavelengths that make up daylight as the sun moves through the sky. Sapphires are at their top color in the afternoon, when the concentration of blue wavelengths is the strongest. Look at them in the morning and the evening, as well, so as to build a full understanding of the gem’s true color. Rubies are at their best at midday, as well as under forms of artificial light with peaks in red wavelengths, so be sure to revisit the stones at other times of day for a full picture.

Do not rely on color memory to choose among stones:

Studies have demonstrated that people have an unreliable memory for color, especially where subtle hues and tones are involved. In gemstones, even subtle differences in color are significant in their value effect. In a secret of the trade, dealers train themselves to remember ideal gem colors by linking the visual information with another sensation, such as taste. When choosing for purchase, try to compare the qualities of gems under consideration in competition with each other - view them at the same time, under the same conditions.

Resist the temptation to buy “in the field”: 

Many factors can affect judgment in the field: the time of day, the degree of cloud cover, the color of the plate on which stones are presented, the traditional strategy by which sellers present their worst stones first to exhaust the buyer’s powers of discernment - all these factors favor the seller and interfere with the buyer’s ability to judge and value stones. Only seasoned dealers have the experience to buy under these conditions. Respect the old adage that, for the retail buyer, the quality of the gem is in inverse proportion to proximity to the mine.

Do not “buy the cert” alone:

Ruffled flag fingerprint in a Burma sapphire, © Aspara

Laboratory gem reports are essential but not sufficient. Other factors count. Freedom from eye visible inclusions, quality of cut, and absence of color zoning are important to consider.

In the end: The Invaluable Certainty of “Certs”

Once science has established that a stone is natural and untreated, and has determined region of origin, all reasonable steps have been taken to establish that a gemstone is truly worthy of purchase.  Buyers can now explore their own tastes and preferences, and enjoy weighing the charms of different stones, factors such as their gracefulness of shape and the subtleties of their hue, tone and saturation. With the certainty of laboratory reports, both the vetting process and the purchase can be fully and confidently enjoyed.

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