Antoinette Matlins, PG, FGA

Frequently Asked Questions

Colored Gemstones  •   Diamonds  •  Pearls

Colored Gemstones

1. I’ve never really understood the terms “gem,” “precious gem,” and “semiprecious gem.” What exactly is a “gem”?
According to the eminent gemologist of the early twentieth century, to be considered a “gem” the material must be beautiful, durable, and rare. In terms of value, we must also add another qualifier: there must be demand! This may seem overly simplified, but it really is a perfect definition. And when we examine it further, these qualifications are all determined by “quality” differences rather than the mineral family. It is quality  that affects “beauty, durability, rarity, and demand.” For example, a very poor quality emerald or ruby will not be very pretty, it will have so many fractures or cracks that it won’t be durable; in such poor quality, it is not at all rare; and, finally, there is no demand for a ruby or emerald of poor quality—they are not pretty and no one would be excited to own one. A poor quality ruby or emerald is not a gem; in the case of the ruby, it is simply a piece of red corundum (the mineral family to which ruby belongs), and the emerald is simply beryl (the mineral family to which emerald belongs).

We also don’t classify stones as “precious” or “semiprecious” today because there are gemstones, such as garnets and tourmalines, that are more beautiful, rare, durable, and costly than the “big four” gems previously known as “precious”—emerald, ruby, sapphire, and diamond (and in some cultures, black opal and imperial jadeite jade were considered “precious” gems). Today it is not the gemstone variety that determines status, but rather, quality differences. A small, fine quality deep green garnet called tsavorite would be more costly—more “precious”—than a low-quality emerald; a brilliant red spinel more costly than a low or medium quality ruby. And a rare, brilliant, “neon” tourmaline from Paraiba, Brazil, will cost as much or more than a rare Burma sapphire.

So don’t think in terms of “precious” and “semiprecious” but instead, think in terms of beauty, rarity, and desirability. These are the factors affecting the “preciousness” of any gem.

2. I’ve been told that all colored gemstones are “treated” so what is a “natural” gem? And why are they treated?
First, it is important to understand that when the jewelry trade makes reference to “natural” colored gemstones today, they are distinguishing those formed in nature from those formed in a laboratory. It is very confusing because most people think a “natural gemstone” is one that was  formed in nature and, apart from the cutting and polishing, is exactly what nature created. Unfortunately, this is not the case; most “natural” gemstones sold today are, in fact, “treated” in some way. So when we say we want a “natural” gem, we must clarify what we mean. Do we mean a “natural” gem that is “not treated in any way,” or do we mean a gemstone that was formed in the earth rather than a lab, and then altered by some type of treatment to appear more beautiful than it would otherwise have been.

Anyone buying any colored gemstone today needs to understand which gems are routinely treated—and which are not—so that you can be sure you get what you really want, and pay an appropriate price. In the case of ruby and sapphire, the routine use of treatments began in the 1960s because demand for these gemstones was increasing while supply was quickly decreasing. The use of heating techniques was introduced to improve the color and clarity of sapphires in the 1960s, and rubies in the 1970s. In the case of emerald, the practice of filling surface-reaching cracks with oil to reduce their visibility is a practice that is centuries old and was considered a “fair trade practice.” (There isn’t enough room here to cover the subject of gemstone “treatments,” but no one buying or selling colored gems should do so without reading my chapter on treatments in Colored Gemtones: The Antoinette Matlins Buying Guide). In general, were it not for the availability of “treated” stones, fine rubies, sapphires, and emeralds would be enjoyed today only by those fortunate enough to be among the world’s most rich and powerful.

Many gemstones in addition to ruby, sapphire, and emerald are treated today, but there are also many gemstones that cannot be improved by gemstone treatments and offer attractive alternatives to anyone seeking a “natural” gemstone. For anyone seeking a truly “natural” gemstone, some of the gems not treated routinely include gems in the garnet family such as tsavorite and mandarin garnet, the spinel family, and chrome tourmaline to mention a few.

3. Are all “treated” gems treated equally, and should I care?

No, all gemstones are not treated equally and it is very important to know the type of treatment used and the extent to which the stone has been treated. In addition, it is important to ask whether or not the treatment is “permanent” and whether or not it affects the durability or wearability of the stone.


1. Can I get a bargain on a diamond by going to a wholesale “diamond district”?
It is usually very difficult for a consumer who is not highly knowledgeable to get a “bargain” in a “diamond district.” The extent of fraud and misrepresentation in wholesale diamond districts has often been found to be high, and often consumers find they have no recourse when they discover a problem. However, if you follow these steps, you should be able to buy with greater confidence wherever you are:

A.  Know what questions to ask—these include getting information about the 4Cs, but there are other important questions pertaining to the settings, treatments, and so on.

B. Make sure the seller is willing to put the answers to all of the questions you’ve asked in writing on the sales receipt. If not, go elsewhere.

C. Find a gemologist-appraiser who holds respected credentials (such as the Master Gemologist Appraiser title, awarded by the American Society of Appraisers) to confirm that the information on the sales receipt is accurate. If not, you’ll have legal recourse. And even in cases where the store has signs saying “no returns” or “no cash refunds,” this does not legally protect sellers who have misrepresented the facts—according to consumer protection laws in the United States they must refund the money.

2. If a diamond has a GIA report, do I need to get an independent appraisal?
Absolutely. How do you know it is a legitimate GIA report? Diamonds have been sold on the Internet with counterfeit GIA reports. Furthermore, the diamond might not match the report—stones do get mixed up unintentionally—or the diamond might have been damaged since the GIA report was issued resulting in a smaller stone, or a lower clarity grade.

3. Experts on the Internet advise against buying a diamond with “strong” fluorescence. What is fluorescence, and should I avoid stones that have it?
Absolutely not! I look for diamonds that have blue fluorescence for many of my clients because not only is it not anything “bad,” but it can be a good thing. And since so many people are afraid of fluorescent diamonds, the price is usually a little less to make them more attractive.

The primary reason for the resistance to buying or selling diamonds with fluorescence is lack of knowledge. Many jewelers don’t really understand fluorescence so they simply avoid it. Despite the positive findings of a study conducted by the Gemological Institute of America several years ago that demonstrated that consumers preferred colorless diamonds with blue fluorescence—“because they look whiter”—resistance on the part of retailers remains virtually unchanged.

Regardless of the benefit of fluorescence, many retailers are quick to point out—erroneously—that “diamonds with fluorescence don’t sparkle as much as non-fluorescent diamonds.” Or, “fluorescent diamonds look oily.” Or, “fluorescent diamonds aren’t as valuable.” The first thing you need to understand is that such comments are overgeneralizations, and while they are sometimes true, they are usually not  true. First, while some diamonds with extremely strong fluorescence can look oily and exhibit less sparkle, many diamonds with blue fluorescence show absolutely no difference in terms of sparkle and personality, and are not only equally alluring, but offer a unique benefit—they look whiter. In terms of value, while stones of the rarest qualities (D-H/Fl–VS) may sell for slight discounts, the vast majority of such stones are actually sold at a small premium.

Fluorescence refers to whether or not a stone produces a color reaction when exposed to ultraviolet radiation—a color seen only when the stone is exposed to ultraviolet radiation. Whether or not a diamond fluoresces, and the strength of its fluorescence (faint, weak, moderate, strong, very strong) is determined by viewing the diamond with a special lamp called an ultraviolet lamp, which emits only ultraviolet radiation. When we say a white (colorless) diamond fluoresces blue, we mean that its color will appear to be blue when we view it under the pure ultraviolet light produced by the ultraviolet lamp. The stone is really a colorless diamond, and will look colorless in normal light. Some diamonds fluoresce while others do not. A diamond can also fluoresce one of many colors, but the most common fluorescent colors seen in diamonds are blue, white, or yellow.

It is important to note whether or not a diamond fluoresces, and what color it fluoresces, because there are varying wavelengths of ultraviolet radiation all around us. Ultraviolet radiation is present in daylight (that’s what causes sunburn) and wherever there are “fluorescent” light fixtures, those long tube lights you see in the ceiling of many stores and office buildings. This means that, depending upon the strength of a diamond’s fluorescence, and the intensity of the ultraviolet radiation in the light source, its color may not appear the same in all lights.

A diamond that has faint or weak fluorescence will have virtually no effect on the appearance of a diamond (although it is worth noting for identification purposes). A diamond that fluoresces medium to strong blue, for example, might appear whiter in daylight, or in an office or store in which there are fluorescent light fixtures because the ultraviolet radiation present will cause the diamond to emit some degree of blue, masking any faint yellow or brown tint that might be present. This is why consumers preferred diamonds that fluoresced blue in the GIA study. Keep in mind that fluorescent lighting is now found in most offices and many stores. In other light sources, the color of a blue-fluorescent diamond may not actually be as white as it appeared in fluorescent light, but since the difference is slight and the personality of the diamond is more lively in other types of light, no one ever notices. What they do notice is the whiter color when seen in daylight or fluorescent light. Clearly, if the fluorescence is so strong that it creates an oily or murky appearance in the stone, or if the personality of the stone seems reduced, I advise avoiding these stones, or, at least, paying much less for them, but this is usually not the case.    

When it comes to diamonds that fluoresce other colors, the presence of fluorescence may be less desirable. For example, if a white diamond fluoresces “strong yellow” it will look less white, even tinted, in fluorescent or daylight, and few people want a diamond that looks “less white” in many lights—unless the price is very attractive. In the case of fancy-color diamonds, the presence of fluorescence can be both good or bad. The presence of blue fluorescence in a yellow diamond may create a slight greenish undertone to the yellow. This might be a very desirable color to some, and undesirable to others. Or, depending upon the diamond, it can even cause a “color-change” effect. I observed a diamond that appeared “fancy green” in daylight, and a pure, vivid yellow in incandescent light, a yellow that had absolutely no greenish tint to the color; it was truly a “color-change” diamond, and this added value.  

But remember, whatever color is produced by fluorescence, it occurs only in daylight or fluorescent light. And when it comes to colorless diamonds, blue fluorescence can be a definite plus—the stone will look whiter, and you may get it for a slightly lower price. >

4. What are clarity-enhanced diamonds and why are they so much more affordable than other diamonds?
A clarity-enhanced diamond is one in which the clarity has been artificially improved. It can refer to a diamond that has been treated by lasering techniques to pulverize or decolorize black inclusions so that they are no longer visible. The results are permanent. In most cases, however, “clarity-enhanced” means the diamond has glass-filled cracks; this treatment results in the cracks no longer being visible and the diamond’s sparkle and beauty are greatly improved. The results of this treatment are not “permanent” and if a jeweler works on a piece of jewelry containing a fracture-filled diamond, the filler might come out, or, in rare cases, the stone could break if the jeweler hasn’t been told the stone is filled before work begins. The filler can be restored if it comes out, and the stones are usually guaranteed by sellers who are honest about what they are selling. There is nothing wrong with buying a fracture-filled diamond as long as you know what you are buying and have paid an appropriate price (usually less than half the cost of another stone of comparable quality).

The biggest problem with fracture-filled diamonds is that they are frequently sold in wholesale diamond districts without disclosure or with a misleading or dishonest explanation as to what “clarity-enhanced” means; most people are told that “clarity enhancement” is simply “part of the cutting and polishing process” and that it “simply makes the diamond sparkle more”!


1. Why does one strand of white cultured pearls cost so much more than another one that’s the same size?
The cost is directly related to quality differences. Many cultured pearls today have a shell nucleus over which the pearl coating is extremely thin. This is true whether you are considering Japanese “akoya” pearls or “South Sea” cultured pearls, whether white, golden, or black. Thin nacre pearls are usually heavily treated in order to make them look like something much more rare and valuable, but the nacre can begin to chip or peel, and eventually you will have little more than shell beads remaining.

Many white cultured pearls are dyed to give them a warm “pink” glow—and then coated with a substance to make them appear lustrous. South Sea pearls in every color may be polished to improve the surface appearance by removing blemishes, to create a rounder pearl, and to increase the surface shine. The color can also be artificially created in black and golden pearls.

Fortunately, if you take the time to carefully examine the costlier pearls—fine pearls with a deep lustrous character that seems to come from the very core of the pearl—you’ll soon be able to spot the “surface shine” of a thin nacre, treated pearl. Also, after handling fine pearls you’ll be able to notice a difference in the “feel” of pearls that have polymer or wax coatings (and they’ll seem too warm to the touch by comparison to other pearls).

It’s important to buy pearls only from a fine jeweler who is knowledgeable about pearls. If buying fancy-color South Sea pearls, I also recommend getting a laboratory document confirming that the color is natural, since the color will dramatically affect the cost.

2. I recently bought pearls and told the jeweler I only wanted real pearls. I took them to an appraiser and found out they were cultured.  What can I do? 
Unfortunately, when we talk about pearls today, jewelers are usually selling either “cultured” pearls or “imitation” pearls, so when you asked for “real” pearls, the jeweler thought you were saying you didn’t want “imitation” pearls. If they wrote “real” pearls on the sales receipt, you shouldn’t have any problem getting a refund because according to the Federal Trade Commission, the term “real pearls” can only be used when selling “natural pearls.” Also, if you are dealing with a fine, reputable jeweler, if you explain that you didn’t get what you thought you were getting, they should be willing to refund your money.

You must understand, however, that for more than sixty years, virtually all pearls sold in any jewelry store in the world have been “cultured” pearls; beautiful “natural” pearls are extremely rare and much more costly than cultured pearls. Most of the oyster beds that provided the fabulous natural pearls, the “real” pearls you had in mind, were wiped out decades ago as a result of pollution and over-fishing. A fine cultured pearl with a thick “pearl” coating around the nucleus is also a costly gem, and these will retain their beauty and value for generations to come. Just be careful not to purchase cultured pearls with an overly thin pearl coating. But if you really want natural pearls (that is, not cultured), you must be prepared to wait to find them, and to pay a high price. For example, a very fine, triple-strand natural pearl necklace sold at Christie’s auction house in Geneva, Switzerland, for over $3 million.

3. What is the difference between a “natural pearl” and a “cultured pearl”?
A natural pearl forms accidentally in a mollusk (usually a saltwater oyster or freshwater mussel), usually around a microscopic intruder such as a sea parasite. The pearl is all “nacre” (the “pearly” substance that builds up to form the pearl) and, because of the way it forms, the shapes are rarely round or symmetrical, the color is rarely white, and divers might open 15,000 oysters before finding one natural pearl of any size and beauty. It also takes many, many years for a pearl of any size to be formed. This is why they are so costly and regarded as one of the rarest of gems throughout history, a gem coveted by the rich and powerful in every age.

Cultured pearls are also formed by the mollusk, but the process is initiated and managed by science and technology—the oysters or mussels are spawned in farms to ensure an abundant supply, the process is started by inserting a round, polished, white shell bead (or, in the case of freshwater cultured pearls, by a piece of mantle tissue and/or a round nucleus of some type) which helps produce a large pearl in a short period of time. The process requires monitoring water temperature, pH balance, and nutritional needs. The nucleus is usually round, to help ensure a larger percentage of round pearls, and the mollusks are also periodically cleaned and rotated to try to ensure a high quality, round pearl. Culturing fine pearls is very labor-intensive, and nature still plays an important role in the final outcome, thus they are also expensive, but not as expensive as a comparable natural pearl. A fine cultured pearl will exhibit a character similar to the natural pearl, and will last for generations.

4. Why are freshwater cultured pearls so much less expensive than saltwater pearls?
Freshwater cultured pearls are produced by different methods than saltwater pearls. With the exception of American freshwater cultured pearls, freshwater pearls are produced in large mussels that produce many pearls simultaneously. Most come from China where they are being produced by the millions. So, while beautiful, they are readily available and this lack of rarity makes them much more affordable than saltwater pearls.

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