Gemstones and Clarity
Opaque, meaning the stone will not transmit light through it.
Translucent, or cloudy, meaning that the stone transmits light, but you cannot see clearly through it.
Heavily Included, meaning that the stone is transparent, but the stone is littered with inclusions, which are very visible without magnification.
Moderately Included, meaning that the stone is transparent, but there are several inclusions, which
are visible without magnification.
Slightly Included, SI, meaning that the stone has some very minor inclusions, which may be visible
without magnification.
Very Slightly Included, or eye-clean, VS, meaning that the stone has some very minor inclusions that are not readily visible without magnification. Some inclusions may be visible without magnification once you see them under magnification and know exactly where to look.
Very Very Slightly Included, VVS, meaning that the stone has some very very minor inclusions, which are difficult to see under magnification.
Loupe clean, or clean, meaning that no inclusions were seen using 10x magnification. However the stone was not examined microscopically. The stone may be internally flawless or flawless.
Internally Flawless, IF, meaning that the stone was examined under a microscope of at least 40x magnification, and no inclusions were seen. The stone has some external blemishes.
Flawless, meaning that the stone was examined under a microscope of at least 40x magnification, and no inclusions were seen and stone has no external blemishes.
Gemstone Treatments and Enhancements
The treatment and enhancement of gemstones has existed for centuries. Some enhancements improve on nature slightly, are undetectable, and they are permanent; this provides the gem market with a larger supply of beautiful gemstones. Other treatments produce dramatic changes in the gemstone; the irradiation and heating of colorless topaz that permanently transforms it into blue topaz is an excellent example. A few treatments are less stable and should be avoided by the knowledgeable buyer.
Generally treatment of a gemstone is done by the cutter or lapidary. Since he makes the investment of buying the gems rough he wants the final product to be as salable as possible. Sometimes gemstones are treated as rough stones. The heating of sapphires and rubies is done before the rough stones are sold to the cutters. Most of this treating is done in countries that cut and mine the stones. By the time the stones enter into the United States market it may have passed through several hands and disclosure of treatment may not always occur.
Ideally disclosure of enhancement is the job of the seller, but it does not always happen. Realistically an informed buyer protects himself. How does treatment affect the price of gemstones? Each gemstone variety must be considered individually as well as each type of treatment. Some gemstones would not be commercially available if they were not enhanced. Citrine and tanzanite are extremely rare in nature; these varieties are dependent on heating to produce enough supply to meet the demands of the market.
There are some gemstones that are not enhanced by present technology; these include: garnets, peridot, iolite, spinel, all varieties of chrysoberyl, catseye tourmaline, malachite, hematite, and all feldspar including all varieties of moonstones. Keep in mind that new technology in gemstone treatment is always changing and new treatments are appearing.
Heating
Heating is the most common treatment; it can improve color by lightening it, darkening it, or it can clarify and brighten gems. In rare cases, it can change the color entirely. Assume the following are heated: rubies, sapphires, tanzanite, citrine, pink topaz, aquamarine, and blue and colorless zircon. Occasionally tourmaline and amethyst are heated to lighten their color. Heating is not generally detectable by today's method and it is irreversible under normal conditions. In general, there is no price difference between heated and unheated gemstones because it is not detectable. In most cases the heating enhances the gemstone to make it more beautiful, so a higher price may result. Tanzanite, citrine, pink topaz, blue and colorless zircon would not be available without heating, so the enhanced product will command a higher price than the rough material from which it originated. However, unheated rubies and sapphires may contain microscopic rutile needles or tiny gas bubbles in pockets of liquid, which are evidence that laboratories can use to guarantee that these stones have not been heated. If these gems are the finest color they will command premium prices due to their extreme rarity.
Oiling
Oiling of emerald is universal; when the rough emerald is mined it is thrown into a barrel of oil; when it is cut, oil is used as a lubricant on the cutter's lap. The colorless oil seeps into the fissures on the surface of the emeralds. When the fractures contain the oil they are less eye visible. To complete this process oil is pressurized into the fissures of the polished stone. No problem, this is the way emeralds are. The only way you will find an emerald that isn't oiled is if there are no fractures at the surface of the emerald, so no oil can get inside the stone. If color is equal, obviously you will pay more for an emerald if it has no fissures that reach the surface; they simply will have fewer inclusions. But remember, if an emerald is put into an ultrasonic or is steamed clean, then the oil may be leached out and fractures could reappear whiter and more obvious. In this case, the stone can be re-oiled.
Rarely you may see a ruby, which is oiled; but only if it is of very low quality. Very rarely colored oils are used on emeralds and rubies. The idea is to add color while concealing fractures. You want to avoid buying these because you can't judge the true color. This is done to deceive the buyer. Fortunately this is not common and it is unlikely you will encounter this if you buy from a reputable source in the United States. Synthetic resins can be used to fill in fractures in emeralds and other stones with fractures that reach the surface of the gem. Hardeners are often applied to make the process permanent.
Irradiation
Irradiation is the bombardment of a material by subatomic particles or radiation. Sometimes irradiation is followed by heating to produce a better or new color for the gem. Blue topaz is the most common example. Although blue topaz occurs in nature, it is quite rare and pale in color. In the United States irradiated gems are regulated by the Nuclear Regulatory Agency to insure there is no harmful residual radiation. You do not have this protection if you buy it out of this country. Today irradiation of blue topaz has created shades not found in natural blue topaz; prices are very reasonable for irradiated blue topaz since there is a great deal of competition in the wholesale end of this market. If you could find an untreated blue topaz of fine color you would pay a higher price if it could be proven that there was no treatment. Tourmaline can be irradiated to darken pink stones into red ones; these are indistinguishable from natural red ones. In this case the tourmalines would sell for the same price if color were comparable. Off colored diamonds can be irradiated and heated and turned into intense greens, yellows, blues and browns. These are not commonplace, but if you are buying a fancy colored diamond particularly a green one, it is a valid question to ask the seller. Irradiated diamonds will sell for much less per carat than the naturally colored ones of comparable color, clarity grade, and size. Cultured pearls can be irradiated to produce gray or blue colors; but dyeing in these colors is more common. Irradiated pearls will sell for about the same price as the dyed pearls, this should be well below the prices asked for pearls with very fine colors.
Dyeing
Dyeing may be good; it may not be good. Without dyeing there would be no black onyx: nature forgot that color in chalcedony! Chalcedony or more commonly known as agate, is often dyed blue, green, or orange and carved into bowls, statues, or cut into beads. The good news is that this stuff does not even look real—it is obviously dyed; but the color is attractive and both buyer and seller are happy. Japanese cultured pearls, which are grown in an Akoya oyster that produces pearls up to about l0 millimeters, grow into a limited selection of colors with various overtones of colors. If they are dark gray, bluish, violet, nearly black, or intense bronze, assume they are dyed. To meet current demand for pearls with rose overtones, some cultured pearls have been given a pink tint; this can be detected by looking for concentrations of dye around drill holes or around blemishes. On the other hand, South Sea cultured pearls, which are generally larger than the Japanese cultured pearls, may grow into a variety of exotic colors naturally because they are grown in a different variety of oyster. Tahitian black pearls are a good example of naturally colored black pearls. Cultured pearls with a natural exotic color will command a much higher price than a dyed one. Dyeing of chalcedony and of pearls is prevalent, permanent, and acceptable. These colors do not occur in nature; no deception is involved. But dyeing of other materials, jade, lapis lazuli, turquoise, and coral, may be less acceptable. Generally, dyeing of these materials is done to disguise poor quality goods. Dyed lapis lazuli can be easily tested by rubbing it with a piece of cotton soaked with acetone (fingernail polish remover). If it is dyed, blue color will eventually rub off on the cotton. Dyed lapis should be much less expensive than fine natural lapis. In the case of lapis lazuli or turquoise, the natural material is not that expensive, so why bother with inferior material unless it is irresistibly cheap? Dyed lapis lazuli may bleed blue onto the wearer or his or her clothing. Dyed jade may be tricky to detect, so be careful if the price seems "too good". Coral beads may also be dyed. But if you are buying your mother-in-law a gift from Waikiki you may justify a purchase of dyed coral beads if they are very inexpensive.
Impregnation and Stabilization
Impregnation and stabilization are common for turquoise. Impregnation is the infusion of wax or paraffin into a porous material. Stabilization is the introduction of a bonding agent, usually plastic, into a porous material. Of the two processes stabilization is the most permanent. Impregnated pieces must be kept away from heat or the wax could melt out. Some gems may have wax applied to the surface to improve the apparent luster; but this is not common. The advantage to stabilized turquoise is that it will not absorb foreign substances and discolor as would untreated turquoise. It should be less expensive than natural, but it is unlikely you will find natural turquoise on the market. Opal is rarely stabilized with plastic to conceal crazing. This is not a commercial product but it could be done to deceive the bargain hunter.
Bleaching
Bleaching is a process for organic gem materials such as ivory, coral, and for pearls and cultured pearls. It lightens the color and is permanent and undetectable. No price difference exists as a result.
Coating
Coating is a process infrequently used where a lacquer or films of some kind is applied to improve a gem's appearance. It is rarely used on diamonds to improve the apparent color of an off-colored stone and deceive a buyer. You probably will not run into this, but coated diamonds should be avoided. Opals may have a black coating on the back to intensify the play of color or to give the appearance of a black opal; this is called a "doublet." It is a fairly common practice and is acceptable if you know what you are buying and do not over pay for it. If an opal presented as natural black opal is mounted in a closed back mounting and it appears to have a black body color, examine the purchase carefully and get a written guarantee describing the material from the seller.
Surface diffusion
Surface diffusion is used on sapphires. Chemicals are infused into the surface at high temperatures. It can improve color or create asterism. If the surface becomes chipped or abraded, it cannot be repolished without removing the color.
Filling
Filling is used on gems with surface fractures or cavities. Glass or plastic or other materials is used to fill these holes. This is sometimes done to rubies. With close examination with magnification you may be able to spot differences in surface luster. This is not an acceptable treatment; it is done to deceive the buyer. Recently a new process to fill fractures in diamonds has been introduced. These are referred to as "Yehuda filled diamonds" after the creator of the process. The filling masks large inclusions that would be visible to the eye. Cracks must reach the surface to be filled; if the diamond is subject to high heat as it would during retipping the filling could melt out. This is considered an acceptable practice in the diamond trade but only if the seller tells you about it. Keep in mind that the original diamond before treatment would have had a very low clarity grade, so the treated stone should be priced accordingly. One difficulty is that you are unable to see what the stone really looks like so it is difficult to know what the price should be.
Lasering
Lasering is rarely used on diamonds; the process drills very tiny holes into a diamond to provide access to an inclusion which detracts from the beauty of the stone. The inclusion can then be bleached to make it less obvious if it is not burned out by the lasering. Under magnification laser holes are easily visible when seen perpendicular to the drill hole. A lasered diamond would be classified in the slightly imperfect or imperfect category regardless of the improvement in apparent clarity and should be priced accordingly.
Infilling
Filling of surface breaking cavities with glass, plastic or opticon to improve the durability and clarity of a gemstone. Hardeners may be used with opticon. This is used frequently on emeralds and rubellite (tourmaline).
Types of Pearls
Freshwater Pearls
Freshwater pearls are best known for their wide range of shapes, sizes, and colors, and their attractive prices. They are produced by the Hyriopsis cumingi mussels, which live in lakes and rivers in remote areas of China. The mussels are nucleated with tiny pieces of mantle tissue, resulting in pearls made of solid nacre. Roughly the size of a human hand, these prolific mussels are able to produce up to 50 pearls at a time, densely clustered on each shell.
Akoya Pearls
Akoya pearls are treasured for their true roundness and highly reflective shine. They are produced by a small Japanese oyster that only produces one pearl at a time. The saltwater Pinctada fucata oyster lives along the coasts of Japan and China. A nucleating bead is surgically implanted in the body of the oyster, which coats it with layer upon layer of beautiful nacre. These relatively small pearls range from 2 to 10 mm; Akoyas larger than 8 mm are quite rare and valuable.
Tahitian and Black South Sea Pearls
Tahitian pearls are the only pearls in the world that are naturally black. Rare and exotic, Black South Sea pearls are produced by the Pinctada margaritifera oyster, native to Tahiti and the French Polynesian islands. These saltwater oysters can grow to be the size of a dinner plate, resulting in luxurious pearls
ranging from 8 to 18 mm in size! Tahitian pearls come in a mesmerizing array of colors, from light silver to deep black, with shades of green, blue, and pink.
White South Sea and Golden South Sea Pearls
White South Sea and Golden South Sea pearls are treasured for their luxurious size and brilliant satin luster. These valuable pearls are produced by the famous silver-lipped oyster, Pinctada maxima, along the coasts of Australia, Indonesia, and the Philippines. As the rarest pearls on earth, a single strand of these
magnificent gems can take many years' of harvests to assemble, as each pearl must be painstakingly matched for size, roundess, color, overtone, and quality.
Mabe and Half Pearls
Mabe pearls are hemispherical cultured pearls grown against the inside shell of an oyster, rather than in the body. They are typically used in settings such as earrings or rings to conceal their flat backs. Mostly produced by saltwater oysters, Mabe pearls are grown in Japan, Indonesia, French Polynesia, and Australia. Although they are beautiful, they do not retain nearly as much value as full round pearls.
