What to Consider When Buying Colored Gemstones

Industry pioneer, precious gem connoisseur and international gem merchant, Jack Abraham is passionate about ruby, sapphire and emerald. In the business for 60 years, Mr. Abraham, was born in Afghanistan and studied in Israel and England before moving to the U.S. in 1962 to study aerodynamics and space exploration. While waiting to receive university exam results from England, he worked with his brother who was a gemstone dealer. Once he got started in the precious gem business, Mr.Abraham was hooked and he never looked back. He has spent his career searching the world for the most magnificent gemstones — specifically rubies, sapphires and emeralds —and educating retailers, dealers, collectors and gemstone aficionados on the ins and outs of buying precious gems. Based in New York City, he curated “Jack Abraham — The Precious Collection” of exceptional colored gemstones and founded his company Precious Gem Resources. His motto is “Professionalism, Trust and Integrity”. With six decades of experience in the business, Mr. Abraham knows that there are many variables when considering a colored gemstone purchase that go beyond liking the color.  To help you get started with your acquisition, Mr. Abraham offers a few pointers on what to look for when buying a precious colored gemstone.

COLOR (primary, secondary and modifiers)

A difference in color between gems can greatly change the price of a stone. If all factors are equal — weight, cut, clarity — the color and whether or not the gem has been enhanced, may cause the price to vary considerably. There are two factors to consider when examining color: Purity and tone. “Color is judged by visible purity of the primary and secondary colors. For example, rubies may have orange, pink or purple modifiers. There may also be negative modifier colors such as gray or brown. All of those color factors will have an impact on the price of the stone,” explains Mr. Abraham.


Tone refers to how light or dark a stone appears, while saturation refers to the depth of color. When a gem is too light, or too dark, it may affect its desirability and value. “A pastel blue sapphire can be beautiful and pleasing to the eye, but it will never command the same price as a sapphire with an intense blue color,” says Mr. Abraham, “These variations in lightness or darkness are tonal references that can make a significant difference in the price of a gem.”


Clarity references the amount of internal inclusions and surface blemishes on the stone, the less the better.

Clarity refers to internal inclusions and surface blemishes. The less of either of those two features the better quality the stone. “The type and number of inclusions can vary dramatically with the particular type of gem. Minor inclusions and surface characteristics may be commonly present even in the finest ruby, sapphires and emeralds.  Sapphires are the cleanest, least included of the precious gems, followed by rubies and then by emeralds. Unlike diamonds, flawless colored gems are almost nonexistent,” comments Mr. Abraham


Size is generally the carat weight of a gemstone. The term carat is derived from the word “carob”. Historically carob seeds, with their fairly consistent weight, were used to measure the size of gem. As weight methods improved, a carat was defined as one-fifth of a gram — meaning that there are five carats in a gram. Mr. Abraham explains further that there is more to size than weight, “Rubies and sapphires, a form of corundum, are denser than diamond. It means that a 2-carat ruby or sapphire cut in an identical shape and form as a 2-carat diamond will look smaller than the diamond of the same carat weight.”


Country of origin has historically dominated demand and dictated market prices for ruby, sapphire and emerald. Burma for rubies, Kashmir for sapphires and Colombia for emeralds have emerged as the most important origins in the colored gemstone marketplace. Country of origin has an enormous impact on the price of colored gemstones. Over the years, gemstone origins have become more complicated as new gemstone sources have been found. “A gem quality Burma ruby with very similar visual characteristics to rubies from other sources can fetch more than 10 times the price in the international market and a Kashmir sapphire as much as 8 times more than stones from other sources,” states Mr. Abraham. The only way to be really sure of country of origin is to have a report(s) from a reputable gemological laboratory verifying origin.


Cut is how facets are positioned on a stone.

Cut is the positioning of facets on a stone. Proportions and finish are two important factors in determining a “good cut”. Some cutters who cut rubies and sapphires, traditionally try to retain as much weight as possible by cutting close to the shape of the rough gem. Symmetry and good proportions are secondary to weight retention and are deemed less important in colored stones than in diamonds. Proportion is how even and pleasing the overall shape of the stone is, with depth and symmetry taken into consideration.  Finish is defined as the quality of polish and symmetry of the gemstone.


According to Mr. Abraham, in the world of ruby and sapphire, most gems will be cut into an oval or a cushion shape with a visually pleasing relationship between the length and width of the stone. A cushion shape is basically a rectangle with rounded corners.  Emeralds are commonly cut in a rectangular faceting style which is a traditional look. With the right proportions these are elegant shapes and generally maximize the potential beauty of the material. “Beyond these basic shapes, there are many options,” reveals Mr. Abraham. “Some are trendy and others are more traditional. Personal taste plays a role in the selection process.”


Dichroism is when two distinct colors show up in one stone. Uneven bands of color in the stone is known as color zoning.

Dichroism, refers to a “two color” effect that in some cases can be visible even to an untrained eye in any ruby, sapphire or emerald. Certain cutting orientations in these gems provide a very pure color, but other cutting directions can produce a visually distracting two-color effect. Frequently, the shape of the rough gem will dictate to the gem cutter how best to minimize the two-color effect. “The less obvious the second color, the more attractive and desirable the gemstone,” says Mr. Abraham.


Color zoning is when a stone has patches, or bands, of color that are uneven and have varying degrees of intensity. When gem crystals are forming in the earth, various changes in temperature, pressure or the presence of other elements, can change the chemistry of the stones growth process. These changes may result in uneven concentration of color in the stone. Gemstone cutters make every effort to reduce the visual impact of these color zones. “Color zoning is much more common in sapphire and much less common in rubies and emeralds,” notes Mr. Abraham. “Visibility of the color zoning in the normal viewing position of a gem can have an important impact on both desirability and price.”


Texture refers to minute inclusions that interfere with the passage of light in the stone. 

Texture refers to minute, finely disbursed inclusions, or their equivalent which interfere with the passage of light and gives the stone a dull “sleepy” appearance with no liveliness. Generally gemstones with little to no texture are most desired. However, in the case of Kashmir sapphire, it is the faint microscopic rutile threads  that produces the “velvety effect” and enhances the beauty and value of a classic sapphire from that region. If the effect is too pronounced it will decrease the value of the stone. “The most important consideration is whether or not the ‘texture’ adds or detracts from the visual appeal of the gem,” comments Mr. Abraham.


Today, almost all colored gemstones are enhanced to bring out their beauty. Rubies and Sapphires are heated to remove impurities and improve their color. For color to improve, the stone must have inherent qualities that heating brings out permanently. Emeralds, which tend to have fissures, are filled with oil or resin to improve their clarity. “Gems that are natural color with no enhancements are the most highly desired and valuable,” concludes Mr. Abraham.

Select pieces from Jack Abraham — The Precious Collection can be found on Jewelers Circle.

Authored by Amber Michelle

Jade • A Gemologist’s Guide

Pen box – white nephrite jade set with rubies, emeralds and diamonds in gold. Mughal workshops, circa 1650-1680. © Victoria & Albert (V&A) Museum, London.02549 (IS); from the Guthrie Collection. A pen case of such opulence is likely to have been presented as an emblem of office, perhaps to a new Vizer, or Chief Minister.

One of the oldest and perhaps most revered of all gems is jade. Known in China as the “stone of heaven” jade is an ancient gem that has been used to create breathtaking jewelry, but also, going back to the stone age to create such practical items as tools and ritual ornaments. The Aztecs and Mayans used jade for medicinal purposes in addition to using it for jewelry and religious objects. In New Zealand, jade was used in similar ways. Today, in China, jade is part of its culture and jade carving is an important art form.

Despite its long history, jade is a gemstone that is somewhat misunderstood in Western cultures. Jade • A Gemologist’s Guide aims to change that.  Gemologist, author, lecturer and educator Richard W. Hughes, who edits and contributes to the book, notes that while there is a vast amount of literature on jade, there is no volume in English that treats jade as a gemological material. Published in 2022 by Lotus Gemology and sponsored by the Houston Museum of Natural Science, the 534 page book is packed with extensive information on the history, sources, appraisal and identification of both treated and imitation jades as well as stunning images and resources to help further one’s jade knowledge.

Earrings in green tourmaline and chrome green jadeite jade. Known to the Chinese as fei tsui, jadeite is one of the world’s most valuable gems. Photo and jewelry courtesy of Doris Hangartner, Zurich, Switzerland.

“While there are many books on jade, none of them deal with jade as a gemological material. This book was designed to address that gap,” states Hughes. “Thus the extensive chapters on sources, identification and treatments, and the extensive reference lists to aid future research on the subject. In addition, this book was designed to open the eyes of Western readers to the incredible contemporary carving being done in China today.”

Jade has also made a social impact on politics, etiquette, religion and other aspects of society in a way that no other gemstone has. Many of those contributing to the book share their personal stories about jade and how it has influenced or inspired them.

“Imperial Jade” from Myanmar. Speciman: Kiarttichatra Intarungsee. Photo: Wimon Manorotkul/Lotus Gemology.

Divided into five sections, Jade • A Gemologist’s Guide draws upon the expertise of numerous experts in the field of jade, bringing a range of perspectives to this intriguing gem. “Contributors were chosen for their expertise in each area,” explains Hughes, “We managed to assemble a team of people that literally have over 500 years of collective study of jade, making this a resource of knowledge that has no peer in the English language.”

The first section of the book, Part A, Introduction to Jade, includes a history of jade in China, among other topics. “Jade is more than just a gem,” says Hughes. “No matter where it was found in the world, from China through New Zealand, Europe and the Americas, it was considered the most valuable stone. As Saying Chen, a commenter on the book said: The dark caves and wooden houses inhabited by prehistoric humans are the cultural birthplace of jade. During the Stone Age, people around the world polished this hardest gem into weapons, tools, ornaments and ritual objects. Its sculptures unite the power of all things in the universe and the mysterious power of life and death.”

This pendant takes the shape of a dragon with a sinuous body grooved to resemble twisted rope. It illustrates the extraordinary talent of skill of early Chinese jade carvers, in whose hands intractable jade seems a supple and malleable material. Eastern Zhou dynasty, Warring States period, (475 — 221 bce). Photos Metropolitan Museum of Art, New York.

Part B, Jade Around the World, contains essays on the various locations where jade is mined. Part C, Decoding the Enigma Identification and Appraisal of Jade focuses on identifying and evaluating nephrite jade and jadeite as well as jade sold at auction. Part D, Bend Me, Shape Me, Jade Carving, takes a look at the art of carving jade. The final section, Part E, Miscellany, examines jade in art. “Most books on jade come to the subject from an historical/cultural standpoint. But as the title states, this book deals with jade from the gemological standpoint, describing the various types of jade, where they are found, how jade is worked and, particularly, how it is identified and appraised,” concludes Hughes.

To order Jade • A Gemologist’s Guide, visit lotusgemology.com

Featured image (top of page): Carving by Master Tang Shuai is rendered in nephrite from China’s Liaoning province. It depicts Mozi, an ancient Chinese polymath. Mozi (b. 470 bce) was known as the “scientific sage.” His book Mojing contains diverse knowledge about mechanics, optics, geometry, engineering, physics and mathematics. This carving represents Mozi and his book as a scientist, with the design expressing the principle of pinhole imaging. This theoretical foundation of photography was discovered by Mozi more than 2000 years before Newton. Photo: Richard W. Hughes/Lotus Gemology.

Authored by Amber Michelle

A History of Cultured Pearls

The luminosity and luster of pearls along with the warmth they emit when worn against your skin has made pearls one of the most popular gems throughout history. While pearls are in abundant supply today, before the 1920s pearls were hard to come by. That’s because they were formed naturally by mollusks when they got an irritant in their shell. To relieve the annoyance from the intruder, the mollusk formed a coating of nacre over the offending invader which then formed a pearl. It was reason to rejoice when a natural pearl was found because they were so rare. Divers who hunted for these treasures often came up empty handed because it was hit or miss as to whether or not a mollusk would actually have a pearl.

Pearls were so hard to come by that at one time they were the rarest of all gems, reserved for royalty, but that changed thanks to a name that is familiar to many of us – Kokichi Mikimoto, a Japanese vegetable farmer turned pearl farmer. He is widely credited with developing cultured pearls. A cultured pearl is formed when a human places an irritant in a mollusk prompting it to create nacre that forms a pearl, rather than waiting for an act of nature as happens when natural pearls are formed.

How Cultured Pearls Started

Mikimoto was not alone in his quest to culture pearls. Two other visionaries in Japan also contributed to pearl farming: Dr. Tokichi Nishikawa, a marine biologist and Tatsuhei Mise, a carpenter. Both men, working independently of each other at around the same time in the early 1900s, came up with very similar processes to nucleate mollusks inducing them to produce pearls.

In 1902 Mise nucleated 15,000 mollusks, which two years later produced round cultured pearls. He applied for a patent and received the first patent for the production of round cultured pearls. Concurrently, Nishikawa was implanting oysters with nuclei and his method also produced small round cultured pearls. He was granted a patent for the implantation process. Both Mise and Nishikawa used similar nuclei to start the culturing process. Mise used lead and silver nuclei, while Nishikawa used gold and silver in his method. Their pearl culturing process was so similar that it became known as the Mise-Nishikawa method.

Meanwhile, Mikimoto was trying his hand at growing cultured pearls. He used mother-of-pearl as the nuclei in akoya oysters. Mikimoto patented his process in 1908. Four years later he tried the same method on pinctada margaritifera and pinctada maximus oysters. Mikimoto then tried using the Mise-Nishikawa method of nucleation and cultured pearls began to form. By 1921, cultured pearls were on the market. It’s one of the reasons that fashionable women of the Art Deco period were able to adorn themselves with long ropes of pearls, the gems were now readily available at an accessible price point.

However, like any new technology, cultured pearls had their critics. A London-based newspaper wrote an article claiming that cultured pearls were not “real”. The article triggered a dispute over the validity of cultured pearls that resulted in a lawsuit that drew international attention to these gems. Mikimoto won the lawsuit and cultured pearls were on their way to reaching a new popularity never experienced before due to their lack of availability and stratospheric prices.

Cultured Pearl Farms

Today, it is very rare to find a natural pearl unless it is vintage; cultured pearls rule the market. So how exactly are pearls cultured? On pearl farms — in oceans, rivers and lakes — baby mollusks are raised in large nets until they are mature enough to be nucleated, which takes about two years. Skilled technicians then gently and carefully implant a nuclei into the mollusk. From there the mollusk is placed back in the water.

The mollusks are nurtured in the water for anywhere from 6 months to a couple of years. The longer the mollusk remains in the water the larger the pearl. Some pearls are farmed in saltwater while others are farmed in freshwater. The type of water makes a difference in the way a finished pearl looks. Japan, Australia, Indonesia, Philippines and French Polynesia, which includes Tahiti, all produce saltwater pearls. These tend to be higher quality, better shaped and more lustrous than other pearls. Saltwater pearls tend to be white, cream, golden or gray.

Freshwater pearls are cultured in rivers, lakes and ponds. These pearls are mostly grown in China and they tend to have a thicker nacre than saltwater pearls. They are often slightly irregular in shape and don’t have the high luster that is so desirable in pearls. They do come in many colors and shapes.

Both saltwater and freshwater cultured pearls can be quite beautiful. It really comes down to how much money you want to spend and your personal preferences. With a wide array of cultured pearls on the market today, you’re sure to find something that suits your style.

Featured image (top of page): Cultured pearl necklace with a diamond and 18-karat gold bow, courtesy Paul Fisher, Inc.

Authored by Amber Michelle

All jewelry showcased in this blog is available on The Jewelers Circle.

The Wonder of Natural Pearls

Natural pearl and diamonds set in silver topped gold bangle, circa 1880, Photo Courtesy: Faerber-Collection.

In ancient Egypt, Cleopatra bet Roman general Marc Antony that she could host the most expensive dinner party ever. According to the story by Pliny the Elder, a Roman author and naturalist, when the two sat down to dinner, a cup of wine (or possibly vinegar) was placed on the table with one of two large natural pearl earrings that Cleopatra always wore. Cleopatra crushed the pearl, dropped it in the liquid and once it had dissolved, drank it. Needless to say, she won the bet. Pliny the Elder, considered to be one of the world’s first gemologists, noted that the pearls were highly valuable – worth what would be millions in modern dollars.

Reserved for Royalty

While pearls are found in abundance in today’s world, that was not always the case. Pearls were so rare at one time that they were reserved for royalty, no one else could really afford them. At the time, all pearls were natural so it took an accident of nature to create a pearl, there was no human intervention involved in the development of natural pearls.

These precious gems were formed when some sort of organic material found its way into a mollusk. The intruding matter irritated the mollusk and in order to soothe the irritation, the mollusk produced nacre to cover the offending material. As layers of nacre collect, a pearl is formed. Nacre is a combination of the mineral argonite, which is calcium carbonate, and conchiolion, a protein secreted by mollusks.

Most pearls on the market now are cultured. Cultured pearls come from pearl farms and they form when a technician places an irritant into the mollusk so that it will begin creating the nacre that forms the pearl. The mollusks are tended by the farmers who keep them safe from predators and make sure that the water has the proper nutrients. Cultured pearls are the reason that we have readily available access to these gifts from the water at an accessible price point.

While it’s easy enough to find cultured pearls now, finding those natural wonders before cultured pearls were developed was another matter. Pearl divers went deep into the waters — as far down as 100 feet — to find these treasures, sometimes not making it back to the surface. When a pearl was discovered it was cause for celebration, demand was high and pearls were scarce.  Natural pearls have always been rare and what you find on the market today is generally vintage making those pearls even more rare and expensive.

Elizabeth Taylor’s Natural Pearl

Among the best-known natural pearls is La Peregrina. The 50.56-carat pearl has a storied background. Said to have been found in the 1500s in the Gulf of Panama, it was owned by the Spanish royal family for several generations and Britain’s Queen Mary I before finding its way into the jewelry collections of Joseph Bonaparte of France and later Prince Louis Napoleon of France as well as the British Duke of Abercorn. Eventually La Peregrina surfaced at an auction in New York City in 1969 where it was purchased by Richard Burton for Elizabeth Taylor. Ms. Taylor was a true jewelry connoisseur, whose vast collection was filled with outstanding pieces. She also liked a lot of bling, so in 1972, Ms. Taylor and Cartier designer Al Durante created a necklace with diamonds, rubies and cultured pearls to showcase La Peregrina. The necklace was sold at Christie’s New York in 2011 for $11.8 million.

The Baroda Pearls, another famous jewelry example of natural pearls, were among the most expensive jewelry items in the world at the time. The seven-strand natural pearl necklace was part of the collection of the Maharajah of Baroda, an important jewelry collector of the 1800s. The legendary pearls were widely chronicled at the time and were among the most expensive pieces of jewelry of the era. In 2007, the two remaining strands of the Baroda Pearls were auctioned off at Christie’s New York selling for $7 million.

How do you know if a pearl is natural? To verify that a pearl is natural it should be examined with the proper gemological equipment. If you’re considering purchasing a natural pearl, ask for a lab report from a reputable gemological laboratory for assurance that the pearls are what they are represented to be.

Authored by Amber Michelle