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Anniversary Cont...


Alexandrite1Alexandrite2If you love magic, especially the magic of science, you'll love Alexandrite, the color-change gem. Outside in daylight, it is a cool bluish mossy green. Inside in lamplight, it is a red gem, with a warm raspberry tone. You can watch it flick back and forth by switching from fluorescent to incandescent light.

Alexandrite is a gem variety of the mineral chrysoberyl discovered in 1830 in Czarist Russia. Since the old Russian imperial colors are red and green, it was named after Czar Alexander II on the occasion of his coming of age.

Today, fine alexandrite is most often found in period jewelry since newly-mined gems are extremely rare. You'll see fine gems offered at auction with impressive estimates. The original source in Russia's Ural Mountains has long since closed after producing for only a few decades and only a few gemstones can be found on the market today. Material with a certificate of Russian origin is still particularly valued by the trade. Some alexandrite is found in Sri Lanka, Zimbabwe and Brazil, but very little shows a dramatic color change. For many years, alexandrite was almost impossible to find because there was so little available.

Then in 1987, a new find of alexandrite was made in Brazil at a locality called Hematita. The Hematita alexandrite shows a striking and attractive color change from raspberry red to bluish green. Although alexandrite remains extremely rare and expensive, the production of a limited amount of new material means a new generation of jewelers and collectors have been exposed to this beautiful gemstone, creating an upsurge in popularity and demand.

CLEAVAGE Distinct to poor, 1 direction



*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!

Emerald by day and a Ruby by night!

Alexandrite3Alexandrite is a remarkable gem. It is one of the finest color change stones in nature, resembling fine emerald or ruby, depending on the light source. It is so rare, that most people have never seen one. Yet, when the modern list of birthstones was assembled, it was listed as June’s birthstone.

Alexandrite has a distinguished and glamorous past. It was first discovered in the Ural Mountains of Russia in 1830. The Russian imperial colors ware red and green, so it made quite a hit. It was named after Czar Alexander II’s at his coming of age ceremony.

The original source closed after only a few decades of mining. Today they have been reopened, but only produce a few carats a year. In 1987, a new find of alexandrite was made in Brazil. Later, alexandrite discoveries were made in Sri Lanka, Madagascar, Myanmar, and Zimbabwe. However, none of these sites produces as rich and vivid a color change as the original Russian source.

Grading Alexandrite

Alexandrite is a color change variety of chrysoberyl. The closer the colors are to pure green and red, the higher the value. The second consideration is the amount of color change. Alexandrite can exhibit everything from 100% to just 5% color change.

Clarity is another significant grading factor. As with most gems, the majority of what nature offers us is cabbing grade, not clean facetable material. However, with alexandrite, the color change has more effect on value than clarity. For example, say you had two gems weighing a half-carat each. One gem is eye clean, with a 50% brownish/red to greenish/blue color change. The other, an opaque cab with a 100% green to red color change, would be higher in value.

Size is always a significant factor in value. The largest alex known is a yellow/green gem weighing 74.4 carats. The largest Russian gems are about 30 carats. However, the vast majority of alexandrites are under one carat. You can see this reflected in our Price Guide. In sizes up to one carat, top quality natural gems sell for $15,000. Over one carat, the prices range from $50,000 to $1,000,000 per carat!

Distinguishing Natural Alexandrite

We receive many emails asking what an inherited gem is worth. Most people do not realize that there are many synthetic alexandrites and look alikes on the market. Some of these have been available nearly as long as the natural gem.

While determining the exact origin of a gem is a matter for professionals, here is a brief guideline. If the gem has good clarity, strong color change, reasonable size, and your grandmother was not exceptionally wealthy, it is most likely a synthetic.

Source: Alexandrite Gemstone Information and Values by International Gem Society


AmberAmber, fossilized tree resin millions of years old, is a time capsule containing souvenirs from the early history of life on our planet. Ancient beads and carvings testify to the beauty prehistoric man found in this organic gem that glows like honey or drops of the sun. You'll find that its warm shades complement the earth tones in your wardrobe. Amber also looks stunning paired with blues, greens, and grays.

The two main sources of amber on the market today are the Baltic states and the Dominican Republic. Amber from the Baltic is older and more valuable but amber from the Dominican Republic is more likely to have insect inclusions, which are prized by collectors.

The largest mine in the Baltic region is in Russia, west of Kaliningrad. Baltic amber is found in Lithuania, Latvia, Estonia, Poland, Russia, and occasionally washed up on the shores of the Baltic Sea as far away as Denmark, Norway, and England. Other amber sources include Myanmar (formerly Burma), Lebanon, Sicily, Mexico, Romania, Germany, and Canada

REFRACTIVE INDEX 1.540 (+.005 -.001)
SPECIFIC GRAVITY 1.05 to 1.096, usually 1.08. (Air bubbles will lower SG.)

SPECIAL CARE INSTRUCTIONS Avoid rough handling, heat and chemicals. Amber can be attacked, (partially dissolved,) by solvents, alcohol, etc.

ENHANCEMENTS Amber is darkened by heating. If done properly, this also creates the “star spangles” effects. Amber can also be dyed to darken the color.

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!

Source: Amber Gemstone Information and Values by International Gem Society


Amethyst1Quartz is found in abundance from every corner of the earth. In its purest form, quart is colorless, but is most prized for its purple variety- amethyst. Purple has long been considered a royal color, so it is not surprising that amethyst has been so much in demand throughout history. Fine amethysts are featured in the British Crown Jewels and were also a favorite of Catherine the Great and Egyptian royalty. Great thinkers like Leonardo da Vinci believed that amethyst could dissipate evil thoughts and quicken the intelligence.

Amethyst, the traditional birthstone for the month of February, is available in small and large sizes, although as with all gemstones, very large sizes in rich, deep colors have always been rare. Designers celebrate amethyst as the ideal choice for jewelry because of its regal color, variety of sizes and shapes, affordability and wide tonal range from light to dark purple.

Brazil is the primary source of amethyst, and Zambia is a significant source as well.

Darker hues of amethyst are rarely enhanced to perfect their color, although some varieties do respond well to heat enhancement. Your AGTA jeweler can tell you how to best care for your amethyst.

REFRACTIVE INDEX 1.544 - 1.553


ENHANCEMENTS Amethyst can be heat treated to improve the color or change it to citrine. Not common.

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!

Amethyst2Amethyst3Crystalline quartz in colors ranging from pale lilac to deep reddish purple and ranging from transparent to translucent is known as amethyst. Siberian mines once produced the world's finest stones with particularly rich purple color that glowed with reddish and/or bluish highlights. Today the term Siberian no longer is a place designation as the mines are long since worked out, but instead is used a a "grade" term, implying colors similar to the original stones from Siberia.

Today's major sources are Brazil, Bolivia and Uruguay in South America and Zambia in Africa. Brazilian stones can be found in huge sizes, but generally are moderate in color. They often suffer from color-banding, which sometimes is visible despite efforts of the cutter to minimize it.

Many amethyst lovers prefer the usually smaller, but more richly colored stones coming from Zambia and, more recently, from Uruguay.

Very light amethyst which once was considered low grade, has gained a recent boost in popularity by intensive marketing on TV shopping programs and the clever marketing strategy of calling it "Rose de France". To my mind these light stones have their greatest appeal when given fancy and unusual cuts, where the artistry of cutting is more on display than the material itself.

At hardness 7 and with no particular warnings on care necessary, amethyst makes a fine jewelry gem for all purposes. Lower grades of material are cabbed, carved, and made into a great variety of beads and other ornamental objects.

Source: Amethyst Gemstone Information and Values by International Gem Society


AquamarineThe very name aquamarine brings to mind the limpid, clear blue tint of the sea. Legend says that Neptune, the King of the Sea, gave aquamarine as gifts to the mermaids, and from then on, it has brought love to all who have owned it. Aquamarine was long thought to have a soothing influence on married couples, making it a good anniversary gift.

Aquamarines are found in a range of blue shades, from the palest pastel to greenish-blue to a deep blue. While the choice of color is largely a matter of taste, the deeper blue gemstones are more rare. Remember that Aquamarine is a pastel gemstone, and while color can be quite intense in larger gemstones, the smaller aquamarines are often less vivid.

This elegant colored gemstone is the birthstone of March and is the symbol of youth, hope, health and fidelity. Aquamarine was long thought to have a soothing influence on married couples, making it a good anniversary gift.

Aquamarines are mined in a number of exotic places including Nigeria, Madagascar, Zambia, Pakistan and Mozambique, but most of the gemstones available today come from Brazil.

Many aquamarines are greenish when mined and cut. For those who prefer a purer blue, these gemstones are heated to enhance their blue color permanently. Some aquamarine fanciers prefer the greenish hues, saying the greener tones remind them more of the sea. The color tones of aquamarine are subtle and varied. Their soft luster is a wonderful addition to any natural colored gemstone jewelry collection. Your AGTA jeweler will tell you how to best care for your aquamarine.

REFRACTIVE INDEX 1.567 - 1.590
HARDNESS 7.5 - 8
CLEAVAGE Indistinct


ENHANCEMENTS May be heat treated to remove green tint. Very common, undetectable.

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!

Aquamarine is a member of the beryl family, as is emerald. Aqua is known for its blue or blue green coloring, which accounts for its name. The legends behind aquamarine all have to do with the sea and water.

Aquamarine is the birth stone for March. It is a popular gem that wears well, is readily available and moderately priced.

One of the most remarkable qualities of this gem are the sizes it is available in. Gems have been cut that weigh several hundred carats, way too large to be worn. Due to this, the price of aquamarine doesn’t vary in sizes above one carat. A 50 carat aquamarine will be worth the same price per carat as a one carat gem of equal quality. The price is dependent on its clarity, the depth of color and to a lesser extent the purity of color.

Another interesting feature of this gem are its inclusions. Beryls, and aquamarine in particular, are known for having long, hollow tubes. This is a distinctive feature and will identify a gem as a member of the beryl family.

If there are enough of these hollow tubes, cat’s eyes or stars can be produced with proper cutting. A cat’s eye aquamarine is a thing of beauty and is highly prized by collectors. Prices will be very close to that of a clean, faceted gem with the same coloring. Star aquamarine is even more rare than a cat’s eye and can demand a premium price.

This beautiful gem receives its coloring from trace amount of iron. The color can be very light to moderately dark. You will rarely see an aqua that is darker than a Swiss blue topaz and when you do the color is usually enhanced by the way they are cut.

There is a very dark blue aqua that came on the market about three decades ago, called the Maxixe aquamarine. (That is pronounced ma-she'-she.) This is an irradiated product and the color isn’t stable. These have mostly disappeared from the market, but if you are ever offered a very deep blue aquamarine, be cautious. You can distinguish the Maxixe from a natural aquamarine by its pleochroism and its spectrum. In natural aquamarine there is distinct blue and colorless dichroism. The Maxixe aqua has no pleochroism and is blue in every direction. With a spectroscope you will see a narrow line at 6950, a strong line at 6540 and weak lines at 6280, 6150, 5500 and 5810. This is considerably different than natural aqua’s spectrum with a broad band at 4270 and a diffuse band at 4560.

Most aquamarines come out of the ground with a greenish tint. This will disappear, leaving a pure blue color by heating to 375 degrees Centigrade. Heating aqua to remove its green tinting is very common and used to be done as a matter of routine. Now we have a more sophisticated public and many of them are starting to appreciate the slightly green gems, knowing that they haven’t been heat treated. This process is impossible to distinguish, so pure blue aquamarines are described as “probably heat treated.”

When cutting aquamarine, depth of color is usually the primary factor to be considered. Deep designs, like barions and emerald cuts are usually preferred. Faceters should use 43 degree pavilion mains on aquamarine for the highest brilliance. Low crown angles will produce higher brilliance, but higher crowns are often used to deepen the color.

Beryls are some of the easiest gems to polish, with diamond being the most common method. It is probably the high quality of polish that give light aquas such great brilliance they are confused with higher RI gems. While they just have moderate dispersion of .014, light stones with high crown angles will show their spectral colors well. This makes for an outstanding gemstone. While the highest values go to the richer colors, a well cut, light aquamarine is one of the most spectacular examples of the gem world.

Source: Aquamarine Gemstone Information and Values by International Gem Society


AmetrineOccasionally, Mother Nature combines the colors of amethyst and citrine into a single, exciting gemstone we call ametrine. The Anahi Mine in Bolivia became famous in the seventeenth century when a Spanish conquistador received it as a dowry when he married a princess from the Ayoreos tribe named Anahi. Ametrine was introduced to Europe through the conquistador's gifts to the Spanish queen.

Ametrine is as affordable as regular amethyst or citrine, and you can have both gemstones for the price of one. Ametrine is especially inexpensive when you consider that it comes from only one place.

Ametrine is a very durable gemstone suited for everyday wear. Your AGTA jeweler can tell you how to best care for your ametrine.

REFRACTIVE INDEX 1.544 - 1.553



*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!

Quartz which occurs in bands of yellow and purple has been given the name of ametrine (amethyst + citrine). Originally discovered in Brazil, the world's current supply comes from one area in Bolivia. The crystals from this mine often exhibit an abrupt color transition, which probably reflects dramatic changes in temperature during their formation. Much citrine today is produced by heating amethyst, so it is easy to imagine natural heating and/or cooling occurring in such a way as to produce the bicolored quartz. Clarity and good size make it a favored material of gem carvers and cabochon artists as well. Quartz, at hardness 7 with no cleavages, make good jewelry gems, although daily wear in rings will result in eventual dulling of the polish. No special care is required as they are not sensitive to temperature change or household chemicals. Both heat enhanced natural quartz, and synthetic ametrine are on the market and as they are optically and physically like Nature's product, sophisticated gemological testing is necessary to detect them. Initially cutters favored windowed emerald shapes with a 50/50 split of colors, and much of the rough is still cut this way. More recently, however; some cutters have begun to cut a variety of shapes, many of which create internal reflections that blend the yellow and purple into attractive shades of rosy gold and mauve, or create mosaic-like flashes of both yellow and purple.

Source: Ametrine Gemstone Information and Values by International Gem Society


ChalcedonyChalcedony was a treasured gemstone of the ancient world. No important Roman would be without a seal, amulet or signet ring carved in this fine and durable material. The Victorians, too, prized chalcedony for carved cameos and intaglios: its fine texture allows for delicate and intricate workmanship. Jewelry designers today love its glowing translucent tones and its availability in a wide range of colors and shapes, including carvings.

Varieties of chalcedony show an amazing variety of colors and patterns. The translucent stripes and bands of agates, the rich opaque green and brown of fine-grained jasper, the plant like forms of moss agate, the green and red pattern of bloodstone, the rich translucent orange-red of carnelian and apple-green of chrysoprase, and the opaque black of onyx are all faces of the versatile quartz gem.

Durable and easy to care for, chalcedony has a hardness of 7 and enviable toughness even when carved in intricate designs. The seal rings worn by ancient Romans are still in fine shape today. Clean with mild dish soap and let dry. Your AGTA Jeweler will tell you how to best care for your chalcedony.

CRYSTALLOGRAPHY Hexagonal, microcrystaline.
REFRACTIVE INDEX 1.544 - 1.553



*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!

Source: Chalcedony Gemstone Information and Values by International Gem Society


Technically, chalcedony (kal SED' uh nee) is any form of microcrystalline or cryptocrystalline quartz, (meaning any form of quartz whose crystals are too small to be seen without high magnification.)

In common practice, only the translucent, single color types are sold as "chalcedony" whereas the rest of this group are sold under individual variety names, or as jasper or agate. While the definitions overlap, jasper usually refers to an opaque, solid colored stone. Agate is defined either by its translucency, or by having a pattern to its colors.



Agate is distinguished by having multiple colors. While not usually as rich as our crystalline gems, the colors can be quite vivid. Agates are sometimes opaque, but they are frequently translucent, and occasionally completely transparent.

Banded Agates


Banded agates are some of the most popular. They are found all around the world, with Brazil being one of the most productive sources. Note that many of the richly colored, banded agates you see for sale are dyed.

Lace agate is noted for its delicate designs. Mexico is one of the premier sources for this material.

Dendritic, Moss And Plume Agates

Agate3 Agate4

These agates have in common that they contain mineral inclusions which may be any color, but share a roughly tree-like or branching form (dendron = tree). Those which have a more plant or feather-like appearance have been called moss or plume agates, respectively. All agates take a wonderful polish and are tough enough for most jewelry uses. Designers often take advantage of the intriguing patterns these stones have to offer.

Picture Stones

Agate5 Agate6

Some of the most treasured gems are those that show a picture that appears to be taken from nature. Oregon's Biggs Jasper is now the most common source. Bruneau Jasper, from Bruneau Canyon, Idaho, used to be the preferred material. Gems from this locality frequently had blue "skies" which the Oregon material lacks. Unfortunately, a dam has submerged the mining site and the material is now quite rare.

Fire Agate


My appreciation for fire agate has taken time to reach its current high level. Most of the pieces I saw early on were poorly fashioned and of low quality, and frankly, I was not impressed. Since starting this web site, however, I have had the opportunity to see some outstanding specimens and, as a result, my enthusiasm has increased dramatically. Fire agate is a brown, microcrystalline quartz which has a botryoidal, (grape-like,) growth form. It contains layers of plate-like crystals of iron oxide, (limonite,) in various planes within it. The iridescent colors of red, gold, green and rarely, blue-violet, result from interference between light rays traveling through these thin layers. (We see the same effect when looking at the rainbow colors at the surface of an oily puddle of water; or in the "orient" created by the layers of nacre on the surface of pearl.)

Usually, fire agate pockets occur within specimens of colorless, white, or light gray chalcedony. Fire agate is found only in the American Southwest and Mexico and was not brought into commerce until after World War II. This, combined with the fact that it is one of the most difficult cab materials to cut properly, keeps it scarce and mostly unknown to the general public.

In order to best reveal the colors, the overlying layers of chalcedony must be removed from the botryoidal surface creating a freeform shape with a carved upper surface. Such treatment requires substantially more time per piece and tends to elevate cost. This type of fashioning also leads to a lack of calibrated pieces and has prevented the use of this gem in mass produced jewelry items. Good fire agates are as impressive in their color-play as fine black opal, but far less expensive. Additionally, fire agate is as hard and durable as any quartz making it wonderful for jewelry uses, including rings. The colors and form are rich and dramatic and generally appeal strongly to men (although I can personally attest to their appeal to women!)



Jasper is an opaque, solid or patterned variety of cryptocrystalline quartz which consists of very tiny quartz crystals colored by various mineral impurities. The names of various jaspers can come from their color: bloodstone, green, lemon; from their pattern: orbicular, poppy, leopardskin, landscape, Picasso; or from a place name: Morrisonite, Mookite.

All types take an excellent polish, are trouble free to care for, and hardy enough for all jewelry uses. These stones are usually cabbed, sometimes carved, and seldom faceted.

Jewelry use of jaspers goes back into the early history of civilization. Various forms of this material are also frequently made into decorative objects, such as ashtrays or bookends. Jaspers are found all over the world, with certain colors or patterns unique to particular locales. Most bloodstone comes from India, all Mookaite from Australia.

Tigers Eye


Crocidolite, (blue asbestos,) alters to quartz, but while retaining its fibrous structure. This material is frequently stained by iron, giving it a golden brown color. We know this material as tigers eye. Unstained pieces, retaining their original blue color, are called Hawks Eye. There are also pieces with both colors.



In this description, chalcedony will mean any translucent, cryptocrystalline quartz with a single color, whether it has a special variety name or not. The various types differ in color due to metallic impurities, such as iron, nickel, copper, and titanium present during crystallization. This group of stones is usually cabbed or carved, although an exceptional, near transparent piece may be faceted. Chalcedonies are tough gems, good for all jewelry applications and require no special care in wearing or cleaning.



The best-known and generally least expensive variety in this group is carnelian. It ranges in color from yellow-orange to rich, near reddish orange, to orangey brown, and varies from semi-opaque to highly translucent. Carnelian is the only type of chalcedony which is regularly enhanced. Iron is the source of its color and as a result it can be easily heat treated, (even by the sun's heat alone,) to darken red tones as the iron is oxidized. You should assume, unless informed otherwise, that any piece of carnelian has been enhanced in this way. Most commercial carnelian comes from India, but it is mined world wide.


Apple green chalcedony that derives its color from nickel is chrysoprase. Ranging from nearly opaque to nearly transparent, its color spectrum includes olivey, to nearly pure greens of medium tone. Very fine, highly saturated pieces have been successfully misrepresented as Imperial jade. Most chrysoprase sold today comes from Australia. Prase is a darker, less saturated form, rarely seen, which comes from Eastern Europe. There are also very small amounts of a green chalcedony colored by chromium found in Africa, called Mtorolite.

Chrysocolla Chalcedony

Chrysocolla Chalcedony

Marketed as "Gem Silica" this relatively rare, blue to blue-green, opaque to near transparent material is the most expensive type of chalcedony. Found almost exclusively in Arizona its color is due to copper. Those who take the trouble to seek it out and are willing to pay the price are rewarded with a glorious color, (elsewhere found only in the soft gem Chrysocolla,) in a stone that has the durability and hardness of quartz.

Blue Chalcedony

Blue Chalcedony

This material is the darling of today's gem carvers and jewelry designers. Piece after piece is featured in magazines like Lapidary Journal, Modern Jeweler, Metalsmith and Ornament. One look at the ethereal colors in this group will tell you why.

The various blues, each group of which has its vocal supporters, are generally designated by place names. They vary in depth of blue color and degree to which the blue is modified by gray or pink hues. As a group, they vary from pale to medium tones and in degree of translucency.

Some pieces have a slight adularescence that enhances their value. This phenomenon, which reaches its apex in moonstone, is due to light interference from layers of microscopic inclusions and looks like a shimmering, floating, interior light. Mohave and Mt. Airy Blues originate in California and Nevada, respectively and are slightly to moderately grayish blue with a light to medium color range. Blue chalcedony from Namibia, often called African Blue, varies from grayish to nearly pure blue and from light to medium dark. The most unusual type, and arguably the most valuable, is from Oregon. Its blues are modified by slight to moderate amounts of pink, making a noticeably lavender gem, which nonetheless is called "Holly Blue."

Other Chalcedonys

Other Chalcedonys Other Chalcedonys1

Turritella agate is composed mostly of turritella shells, embedded in agate.

Iris agate shows iridescent colors reflecting from between the color layers.

Sard is similar to carnelian, but with a brownish tone and more opaque.

Prase is a green, or yellowish green chalcedony.

Plasma is a dark green, opaque variety. It frequently has white or yellowish spots.

Bloodstone, or heliotrope, is plasma with red and orange spots of iron oxide.

Onyx is a chalcedony with straight bands of colors. Black onyx occurs in nature in thin bands. What you find in the stores is almost always dyed.

Sardonyx is onyx with white and red layers.

Flint and chert are opaque, dull gray or white. They rarely make an appearance as gems, but are useful materials for arrowheads, driveways, and other utilitarian purposes.

Other Chalcedonys2

Petrified wood and dinosaur bone are primarily chalcedony in their modern composition. The lapidary will cut and polish them like any other quartz family gem.

Source: Agate Gemstone Information and Values by International Gem Society


CitrineNamed from the French word for lemon, "citron" since citrine has a juicy lemon color. In ancient times, citrine was carried as a protection against snake venom and evil thoughts.

Sunny and affordable, citrine can brighten almost any jewelry style, blending especially well with the yellow gleam of polished gold.

It is the most affordable of all the earth-toned gemstones and is the alternate birthstone for November. Brazil and Zambia is the primary source of this gemstones.

Brownish varieties are commonly heated and magically turn into the bright yellow or orange colors known as citrine. This enhancement method is permanent and will last for the life of the gemstones. Your AGTA jeweler can tell you how to best care for your citrine.

REFRACTIVE INDEX 1.544 - 1.553


ENHANCEMENTS Amethyst can be heat treated to change it to citrine. Not common. "Madeira" Citrine" with red flashes is a result of heat treatment.

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!


Citrine, yellow to red-orange quartz, was once the Rodney Dangerfield of the gem world; its sheer abundance being responsible for this "no respect" treatment. That has begun to turn around somewhat in the last couple of decades as fashions have repeatedly emphasized earth tones and home shopping networks have marketed the various shades of citrine aggressively with catchy adjectives like "butterscotch" and "whiskey".

Actually, very little of the quartz which is mined is citrine. Natural stones tend to be pale yellow, often with smoky tones. The vast majority of citrine which is marketed is produced by heating smoky quartz, (which produces light to medium yellows,) and amethyst, (which produces stronger yellows and orange-red to orangey brown shades.) The treatment is usually done right at the mine, and is stable, and fully accepted within the gem trade. Recently, colorless quartz from some mines have been irradiated and heated to produce a neon, slightly greenish yellow, usually called Lemon Quartz.

In the past, it was commonplace for citrine to be given misnomers such as, "Brazilian topaz", "Madeira topaz," etc. The higher gemological knowledge level of both jewelers and the public make this practice rare today. This gem is a fine jewelry stone, with no cleavage and a hardness of 7. Furthermore, its availability in large sizes enables cutters to use it for dramatic and intricate custom cuts. It is also used for gem carvings. Stable in light and not very sensitive to chemicals, this stone requires no special care and can be used for any jewelry application. Virtually all citrine comes from Brazil.

Source: Citrine Gemstone Information and Values by International Gem Society


Diamond1Diamond is celebrated for the purity of its brilliance. Yet within the structure of diamond, we often find impurities, or inclusions, that deflect light, distracting our eye from the radiance we so value. Many of these tiny imperfections are removed when the diamond is shaped. Today, cutters also have the option of using an enhancement technique that focuses tiny beams of laser light at imperfections and vaporizes them. The minute passageways created by the laser may then be filled with clear resins or glass-hard substances, rendering them nearly invisible to the naked eye. This method can also be used to fill fissures that reach the stone's surface, rendering them less visible to the naked eye. This treatment is permanent: only extreme heat or specifically formulated chemicals will remove the filling from the laser passageways or fissures.

Diamonds may also be colored in a variety of hues. Extreme heat and irradiation permanently enhance certain innate color properties, allowing them to display their hues in more brilliant array. Black diamonds, for example, are usually enhanced in this way.

A new high-pressure high-temperature treatment, known as HPHT, can improve the color of certain types of diamonds. HPHT treatment can remove tints from some diamonds, making them more colorless, or intensify the pink, blue, green, and yellow colors in others. Because HPHT diamonds sell for less than naturally colored diamonds, industry rules require HPHT-treated stones to be identified with an inscription on the girdle of the diamond to prevent misrepresentation.

Whether color enhanced, lasered, or cut from the most perfect raw state, your jeweler will inform you of the magical journey your diamond has followed, from deep within the earth's mantle to the fine, finished gemstone you see before you. Your AGTA jeweler will tell you how to best care for your diamond.

CLEAVAGE Perfect 4 directions


ENHANCEMENTS Some colors produced by irridation, common. Laser drilled to remove inclusions, common. Cracks filled with glass, occassional.

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!

Diamonds are our most popular gem. They have great brilliance, plus the delightful quality know as fire, or dispersion. (That is the ability to take in white light and throw back flashes of color.)

Diamonds are graded into dozens of categories. While this is helpful to the professional, it can be confusing to the average consumer. I especially feel for the young couple looking for their first diamond engagement set. They want to gather enough information to make an intelligent decision, but can be overwhelmed by all the data thrown at them.

To help you I have done two things. First, there is a description of how diamonds are graded. Once you understand that, I make recommendations on choosing a diamond. Please read on HERE.


EmeraldThe ancient Egyptians mined emeralds nearly 4,000 years ago, and Cleopatra was an avid collector. South America's rich bounty of emeralds was discovered by 16th Century Spanish explorers who found large emeralds in the possession of the Aztecs and Incas. Believed by the ancients to empower the owner with foresight into the future, emerald is regarded as an amulet for good fortune

Emerald, to many, symbolizes rebirth and the abundance of the life force. The rich green hue brings to mind the regeneration of life in spring and hope of new possibilities. Emerald is the birthstone for May and a talisman for Gemini.

Spring can also be seen in the network of inclusions in the depth of the emerald that the French call the jardin, or garden, because it resembles foliage. The inclusions are like a fingerprint, giving each emerald a distinct personality and distinguishing them as truly natural gemstones.

Today, most of the world's emeralds are mined in Colombia, Brazil and Zambia. Emeralds can be cut in a variety of different shapes, ranging from the traditional rectangular step-cut, known as the "emerald cut," to rounds, ovals, squares and cabochons.

Early gemstone merchants sought to purify the transparency of their emeralds by immersing them in clear oils or paraffin. They found that clear oils and waxes rendered surface fissures less visible to the eye. Today, we have many sophisticated technologies with which to clarity-enhance emeralds. In addition to the oils and waxes of ancient methods, we now use clear resins to penetrate the open fissures surfacing in the stones. Hardeners are often added to solidify these liquids. This step prevents the resin from evaporating, thus making the clarity enhancement more permanent than oiling or waxing the gem. Although emerald itself is quite durable, the garden of inclusions may make individual gems vulnerable to damage if handled roughly. Your AGTA jeweler can tell you how to best care for your emerald.

CHEMISTRY Be3Al2Si6)O18 + Cr
REFRACTIVE INDEX ~ 1.57 - 1.59, varies with source.
HARDNESS 7.5 - 8
CLEAVAGE Indistinct

WEARABILITY* Poor to Good, depending on the intergity of the gem.
SPECIAL CARE INSTRUCTIONS Emeralds usually have internal fracutres, so clean with warm or room temperature soap and water. Avoid wearing gem where it will get rough treatment.

ENHANCEMENTS Oiling, common. (Oils and epoxies are used to fill fractures, which reduces their visibility.

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!

Since the time of Cleopatra, emeralds have epitomized the of color in green gemstones. It would be easy to question this statement if all one had seen of emeralds were the commercial, (and poorer,) quality stones which abound on home shopping networks and in some jewelry stores. A fine emerald, though, is a truly breathtaking sight and is well deserving of its placement in the traditional "big four" along with sapphire, ruby and diamond. Emerald is the birthstone for May and for commemorating the 20th and 35th wedding anniversaries.

The center of world emerald mining is in South America with Colombia and Brazil as major producers. The African mines that supplied Cleopatra's passion have long since been played out. However, today the African continent is second only to South America in production, with mines in Zambia, Zimbabwe, Madagascar and Nigeria.

Each of these world locales typically produces a certain color, size and clarity -- so much so that the term "Colombian" emerald has often been enthusiastically used to describe vivid, slightly bluish green stones of medium to medium dark color, no matter what their actual geographic origin. Likewise, emeralds of lighter color are sometimes called "Brazilian", even if they were mined in Africa. The USA and Japan together purchase more than 75% of the world's cut emeralds.

Emerald, by definition, is a medium or darker green to blue green beryl, in which the green color is derived from impurities of Chromium, Vanadium, or a combination of both. Before 1963 the definition was limited to Chromium containing stones, but the discovery of a large deposit of Vanadium colored stones in Brazil led to modification.

Varying amounts of iron will affect the color as well, with more atoms of this impurity increasing the bluish tones. In a situation similar to that which exists with the boundary between pink sapphire and ruby; there are chromium colored stones of light to medium light green color which are sometimes sold as emerald, but which are more correctly considered green beryl. Geological conditions were right, it seems, in Colombia to produce exactly the slightly bluish green shade and strong saturation that make stones from that locale the epitome of the variety.

Emeralds are considered a "Type III" gemstone by GIA which means that they are virtually always included to one degree or another. Because of this designation, a clarity grade of "very slightly included" for example, refers to the normal range for emeralds, not for all gemstones. Well over 90% of the emeralds in commerce have been treated to minimize the appearance of the inclusions.


The industry practice for treatment, (and that which is considered "standard" by AGTA,) is "oiling". This term refers to the practice of immersing emeralds in a colorless oil or resin. Often this is done using a vacuum chamber to assist penetration. Non-standard treatments go beyond this to using green colored oils and hardened, epoxy-like resins.

These treatments dramatically improve the appearance of the gems, but necessitate special care in cleaning and setting. Steam cleaners, solvents and ultrasonics can remove the oils, making inclusions which had barely been visible stand out in sharp relief. Luckily, it is possible to have emeralds re-oiled.

The inevitable inclusions are more than a aesthetic consideration, as they can reduce the structural integrity of the gem as well. Beryls, in general, are good jewelry stones, with a hardness of up to 8 and no troublesome cleavages. Because of the inclusions, emeralds are generally more fragile than other beryls and must be treated more gently.

Emerald imitations often encountered in the marketplace include: glass, YAG, synthetic spinel triplets, green cubic zirconia, and beryl triplets. Within the last fifty years two major processes have been developed to produce "lab created" emeralds, or synthetics. If you've seen and priced man-made emeralds you might have wondered why they are so costly compared to CZs or some types of synthetic sapphires. Both the flux and the hydrothermal methods of production require costly equipment and are energy intensive. They take a long to time produce and have a low yield of cuttable gems.

Some of the first lab created emeralds on the market weren't convincing because they were so clean, but the sophistication of today's consumer has led to a trend toward more naturally included looking synthetics. Although this improves their acceptability, it does make it a little more difficult for gemologists and appraisers to prove natural origin. Fortunately, there are signs, particularly regarding the types of inclusions in a gem, which can conclusively verify natural versus synthetic origin.

Source: Emerald Gemstone Information and Values by International Gem Society


GarnetGarnet traces its roots to the Nile Delta in 3100 B.C., where Egyptian artisans would craft the gemstone into beads or inlay them into hand-wrought jewelry. Noah used garnet as a lamp on his bow as he cast about on the ocean. Garnet received its name from the ancient Greeks because the color reminded them of the "granatum," or pomegranate seed.

The versatile garnet comes in a virtual rainbow of colors, from the deep red Bohemian Garnet to the vibrant greens of the Russian demantoid and African tsavorite. The oranges and browns of spessartite and hessonite hail from Namibia and Sri Lanka and the subtle pinks and purples of the rhododendron flower, are also yours to explore.

Garnet is the traditional birthstone for the month of January, however, red need not be your color of choice if you are born in this month. Rich orange and golden hues, striking greens, petal soft colors of violet and lavender, all await your selection.

Most commonly found in round, oval, and cushion cuts. Availability depends on variety: tsavorite is very difficult to find in sizes above a carat or two, while rhodolite garnet is available in larger sizes.

This durable and brilliant gem is easy to care for with mild dish soap: use a toothbrush to scrub behind the gemstone where dust can collect. Your AGTA jeweler can tell you how to best care for your garnet.

Garnet comes from the Latin word, "granatus" which means grain. That is because many garnet deposits are small grains of red crystals in or on their host rock.

Garnets have several species, as well as several varieties. They are listed here, with more detailed information after the general descriptions.



This garnet is named after Spessart, Bavaria.

Spessartite is somewhat rare. As with the other garnets, it always occurs in a blend with other species. Gems with the highest spessartite content are a light orange. Those with an almandine content are reddish, to red brown in hue.

The most valuable spessarties are a bright, orangish red. These come from Ramona, California, and Amelia, Virginia.. Andradite

HARDNESS 7 - 7.5



Andradite is named after the Portuguese mineralogist, d’Andrade.

This is one of the rarest and most sought after garnets. There are no major sources of andradite and the supply is limited to small deposits.

Its dispersion is much higher than any other garnet and even much higher than diamond. The dispersion is usually masked by dark body colors but small, light colored gems are dazzling!

The variety dematoid is colored green by chromium. This gem is always in high demand.

Andradites are known for their distinctive, horsetail inclusions. (See "Identifying Inclusions" in our Reference Library.) They are both an aid to the gemologist and a delight to collectors.

HARDNESS 6.5 - 7



The botanical name for gooseberry is grossularia, from which this garnet receives its name.

Unlike the other garnets, grossulars are rarely red or dark. They come in every color except blue and are sometimes colorless. The tone is often light to medium. They make brilliant gems with vibrant colors.

HARDNESS 6.5 - 7.5



Hydrogrossular differs from the other garnets in that it is never transparent. It ranges from translucent to opaque. The most common color is a bluish green, but they are also found in pink, white, and gray.

Because of its coloring and translucency, hydrogrossular is often used as a jade substitute. Large pieces are available, which lend themselves to carving..

CHEMISTRY Ca3Al2(SiO4)3-x(OH)4
HARDNESS 6.5 - 7.5



Uvarovite is named after Count S. S. Uvarov, (1765-1855), president of the St. Petersburg Academy and mineral collector.

This is the rarest of the garnet family. Colored by chromium, it is always a dark, rich green. The crystals are small and most people have only seen examples of druzy on matrix.

The crystals are usually opaque. Only small corners of larger crystals have the transparency for faceting. Anything over one carat is exceptionally rare for a faceted uvarovite. Collectors are grateful to have a faceted uvarovite of any size. They are so rare; there simply are not enough to go around.

HARDNESS 6.5 - 7.5

Garnet Varieties



Some say the name rhodolite comes from the Greek word, rhodon, meaning rose. Other scholars compare the name to rhododendron. In either case, the name is comparing the color to a flower.



Malaia is a Bantu word that means out of the family, or out of the tribe. It is also used to mean prostitute or deceiver. It came into usage for a number of garnets that did not fit into any of the standard categories.



Demantoid comes from the French, "demant," meaning diamond. The reason is obvious, with its high brilliance and dispersion. Dematoid garnets are a green variety of andradite. They are known for their golden, "horsetail" inclusions.



Tsavorite is named after its only source, the Tsavo Valley in Kenya. It is the chromium colored, green variety of grossular.

These popular gems demand high value in today’s market. While faceted stones approaching 20 carats are known, their deep coloring usually keeps their size below three carats.



Hessonite is from a Greek word meaning inferior. This refers to it having less hardness than other garnets.

Hessonites are an orangish variety of grossular garnet. Sometimes their coloring leans towards the pink. Asbestos, Quebec is one of the most common sources. The miners find pinkish orange crystals among the asbestos. Africa is also a major source for hessonite.

Color Change Garnets


Any gem that changes color is a rare find and a treat for collectors. Garnets exhibit the widest variety of color changes in the gem world, with almost every hue exhibited.

It is commonly said that garnets come in every color of the rainbow except blue. This is still true in natural light, but there are recent discoveries of garnets that turn blue in artificial light.

Color change garnets are mostly pyrope and spessartite in composition. Except for the color change, they are identical in properties to the Malaia variety. Their primary source is Africa.

Idaho garnets, which are primarily almandine/pyrope mixtures, occasionally show a strong color shift from red to purplish red.



Pyrope comes from a Greek word meaning "fire like." The common dark red garnets are a mixture of pyrope and almandine.

One popular garnet is chrome pyrope, whose color rivals ruby. These are found in Arizona, where ants bring them to the surface. Hence, they are dubbed, “ant hill garnets.” While their color is superb, they are very dark in tone. Gems are rarely faceted in sizes over one carat because of this.

HARDNESS 7 - 7.5



One of the classic sources of this garnet is Alabanda, in Asia Minor. Its common name is a modification of the source. The Roman historian Pliny wrote of them.

Our common, dark red garnets are a blend of almandine and pyrope. Throughout history, this has been one of the most popular gems. They are found world wide and in great abundance. Hence, the value is low.

Very large crystals exist, but because of their dark tone, only small to medium sized gems are faceted. These are cut very shallow, to let light pass through.

Almandine garnets from Idaho and India sometimes have asbestos fiber inclusions. These will produce star stones when properly cut. They are highly prized by collectors, because of their rarity. They are also one of the most difficult gems to cut.

HARDNESS 7 - 7.5



In Greek mythology, Proteus was a sea god, capable of changing his shape. It has become a noun for one who easily changes their appearance or principles.

Proteus are the only treated garnets. All the others resist change, but a few almandine/pyropes from the US will change into Proteus. The treatment brings a thin layer of metals to the surface.

This causes it to have a dual appearance. In reflected light, they have a dark gray, metallic luster, much like hematite. In transmitted light, the dark red of the garnet shows through.

Source: Garnet Gemstone Information and Values by International Gem Society


IoliteThis stone, which represents one of the few relatively available and affordable blue stone options, is rapidly gaining in popularity. Arguably the gain is due more to exposure in mail order catalogs and on cable shopping channels than to promotion by traditional jewelry stores. Run of the mill stones often have a steely, inky or washed out blue color, but the best specimens can rival AAA tanzanite in the saturation of their blue-violet hue.

Iolite is frequently step cut to enhance color and often windowed and/or shallow cut to lighten tone. The cutter must orient the rough carefully, taking iolite’s trichroism of blue, gray and near colorless into account. So far, no treatments have been successfully used to lighten color or to remove inclusions, so one can assume that gems are untreated.

Its hardness of 7-7.5 makes it a suitable jewelry stone, though the presence of cleavage must be taken into account and some care exercised. Most of the iolite in world commerce comes from India, but substantial amounts are also mined in Tanzania, Brazil and Sri Lanka.

COLOR Blue, Purple, Gray
HARDNESS 7 - 7.5
SG 2.6 - 2.7
TRANSPARENCY Transparent to translucent
LUSTER Vitreous

Source: Iolite Gemstone Information and Values by International Gem Society
Image Source: GIA


KunziteSurprisingly Kunzite was discovered in the United States, early in the twentieth century. Even its name has American roots: this pink gem variety of the mineral spodumene is named in tribute to George Kunz, the legendary gem scholar, gemologist, and gem buyer for Tiffany & Co at the turn of the century. The author of The Curious Lore of Precious Stones, Kunz searched the globe for old stories and legends about gems as he searched for new varieties and new deposits.

Kunzite was first found in Connecticut, USA. But the first commercially significant deposit was discovered in 1902 in the Pala region of California, where morganite beryl was also first discovered. The name was a brilliant marketing move: the miners named the gem after its most likely customer, Kunz.  Morganite was named for the customer’s customer: J.P. Morgan.

Today most kunzite is mined in Brazil, Afghanistan, and Madagascar. Kunzite is often found in association with morganite and pink tourmaline, the other popular pink gemstones.

Kunzite is relatively hard, but should be handled with care because, like diamond, it has a distinct cleavage. A sharp blow, if it lands in the wrong place, can break it in two. Kunzite should also be protected from heat and continued exposure to strong light which may gradually fade its color. Clean with mild dish soap: use a toothbrush to scrub behind the stone where dust can collect. Your AGTA jeweler will tell you how to best care for your kunzite. Today most kunzite is mined in Brazil, Afghanistan, and Madagascar. Kunzite is often found in association with morganite and pink tourmaline, the other popular pink gemstones.

Kunzite is relatively hard, but should be handled with care because, like diamond, it has a distinct cleavage. A sharp blow, if it lands in the wrong place, can break it in two. Kunzite should also be protected from heat and continued exposure to strong light which may gradually fade its color. Clean with mild dish soap: use a toothbrush to scrub behind the stone where dust can collect. Your AGTA jeweler will tell you how to best care for your kunzite.

HARDNESS 6.0 - 7.0.
OCCURRENCE Brazil, Madagascar, Myanmar (Burma), U.S., Canada, former USSR, Mexico and Sweden.
APPEARANCE Lilac pink (colored by manganese), named after the gemologist G.F. Kunz who described it in 1902. Kunzite has strong pleochroism, showing colorless and two shades of color when viewed from different directions. Kunzite is a fragile stone. Called an "evening" stone, it should not be exposed to direct sunlight which can fade it's color in time.

ENHANCEMENTS Kunzite is commonly heat treated to improve color from certain locations. Kunzite is also commonly irradiated and heat treated to darken color.

Source: Kunzite Gemstone Information and Values by International Gem Society


MorganiteMorganite is the soft pink, sometimes peachish to violet color of beryl, colored by manganese.

Morganite was first discovered in California in the early twentieth century. A rich gem find of tourmaline, kunzite, and other gems outside San Diego started a gem rush in the region.  Morganite was an exciting new discovery, one that drew the attention of the world's most important gem buyer: George Kunz of Tiffany & Co. He decided to name it in honor of his biggest customer: millionaire bank tycoon J.P. Morgan, who was an avid gem collector.

Although its color is pastel, it has a lushness rare in pink gemstones.

There are deposits of this gemstone in Brazil, Mozambique, Namibia, Afghanistan, and Russia.

Morganite is a durable gemstone perfect for everyday wear. Clean with mild dish soap: use a toothbrush to scrub behind the stone where dust can collect. Your AGTA jeweler will tell you how to best care for your morganite. Morganite is a durable gemstone perfect for everyday wear. Clean with mild dish soap: use a toothbrush to scrub behind the stone where dust can collect. Your AGTA jeweler will tell you how to best care for your morganite.

REFRACTIVE INDEX 1.600 - 1.560
HARDNESS 7.5 - 8
CLEAVAGE Indistinct



*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!
For more details see the article on "Hardness and Wearability."

Source: Morganite Gemstone Information and Values by International Gem Society


OpalRevered as a symbol of hope, fidelity, and purity, opal was dubbed the Queen of Gems by the ancient Romans because it encompassed the colors of all other gems. Opal is prized for its unique play of color, the ability to diffract light into flashes of rainbow color.

Opal occurs in different colors, ranging from semi-transparent to opaque. The most common is white opal. Crystal or water opal has a colorless body. The most valued variety, black opal, has a dark blue, gray, or black body color. Boulder opal combines precious opal with the ironstone in which it forms. Bright yellow, orange, or red fire opal are quite different from the other varieties of opal. Their day-glo tones, which are translucent to transparent, are beautiful with or without play of color. Opal, along with tourmaline, is the birthstone for October and the suggested gift for the fourteenth anniversary.

Today's supplies of opal come primarily from Australia, Mexico and the United States. Most opals are not faceted but cut into rounded or free-form cabochons that enhance their play of color.

Although opal is rarely enhanced by methods other than cutting and polishing, opals can be treated to bring out their play of color. One technique is to immerse white, gray, or black opal in a sugar solution and then in strong sulfuric acid, which carbonizes with the sugar and leaves microscopic carbon specks that blacken the body color, making its flashes of color more visible. Opals can also be permeated with colorless oil, wax, resin, plastic, and hardeners to improve their appearance and durability. Occasionally, some thinner or translucent opal may be painted with a black epoxy on the backside of the gemstone to darken the body color and improve the play of color. Fire opal is not commonly enhanced.

Opal, with or without enhancement, should be treated with some care. Opal is softer than many other gemstones and should be stored carefully to avoid being scratched by other jewelry. It should also be protected from blows, as exposed corners can chip. Opal should not be exposed to heat or acid. Your AGTA jeweler will tell you how to best care for your opal. Today's supplies of opal come primarily from Australia, Mexico and the United States. Most opals are not faceted but cut into rounded or free-form cabochons that enhance their play of color.

CHEMISTRY SiO2 . nH2O. Water usually 6 to 10% in precious opal, can be as high as 21%.
HARDNESS 5.5 - 6.5

SPECIAL CARE INSTRUCTIONS Very heat senstive, clean with warm or room temperature soap and water. Avoid wearing gem where it will get rough treatment.

ENHANCEMENTS Impregnated with oil, wax, or plastic. Occasional. Smoked, to create black opal. Occassional. Treated with dye or chemicals to make light opal black. Occasional.

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!
For more details see the article on "Hardness and Wearability."

Source: Opal Gemstone Information and Values by International Gem Society


PearlAccording to ancient Chinese legend, the moon holds the power to create pearls, instilling them with its celestial glow and mystery. Pearls have been treasured for their lustrous, creamy texture and subtle iridescent reflections since the dawn of humankind.

Pearls are unique in the world of colored gemstones since they are the only gemstone formed within a living creature. Because natural pearls are so rare and difficult to recover from the ocean's depths, man invented the technique of culturing salt and freshwater pearls from mollusks carefully seeded with irritants similar to those produced by nature. The painstaking effort of culturing is one of the most dramatic examples of man's quest to coax beauty from nature.

Today, cultured pearls are grown and harvested in many parts of the world including the fresh waters of the Tennessee River. The majority of cultured pearls come from Japan, China and the South Pacific.

Cultured pearls come in many beautiful colors including: gold, yellow, champagne, pink, peach, lavender, gray and black. Cultured pearls come in many shapes and sizes, and can be acquired in both graduated and uniform strands. They can be purchased singly or in pairs for rings, pendants and earrings. June birthdays and third and thirtieth anniversaries are celebrated with the gift of pearls.

Due to demand for perfectly matched white pearl strands, cultured fresh and saltwater pearls are often bleached to achieve a uniform color. They may also be polished in tumblers to clean and improve their luster.

Dyes, heat treatment, and irradiation are sometimes applied to produce a wide range of hues such as yellow, green, blue, purple, gray, and black in freshwater and Akoya cultured pearls. Some South Sea cultured pearls are bleached to lighten their hue, but most South Sea and Tahitian cultured pearls are not subjected to enhancements to create or improve their color.

Pearls require special care because they contain calcareous crystals that are sensitive to chemicals and acids. To care for your cultured pearls, avoid using perfume, hairspray, abrasives, solvents, and nail polish removers while wearing them. Like your skin, cultured pearls contain water and may dehydrate and crack if exposed continuously to arid conditions. Your AGTA jeweler will tell you how to best care for your cultured pearls.

CHEMISTRY CaCO3 (aragonite, the outer layer) about 82 - 86%, conchiolin 10 - 14%, water 2%.
CRYSTALLOGRAPHY Aragonite is orthorhombic, with crystals radially oriented.
HARDNESS 2.5 - 4.5

SPECIAL CARE INSTRUCTIONS Avoid heat and all chemicals, including perfume and other cosmetics.

ENHANCEMENTS Dying, common

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!

Source: Pearl Gemstone Information and Values by International Gem Society


PeridotPeridot is treasured in Hawaii as the goddess Pele's tears. The island of Oahu even has beaches made out of tiny grains of peridot.  Although Hawaii’s volcanoes have produced some peridot large enough to be cut into gemstones, virtually all peridot sold in Hawaii today is from Arizona, another state with extreme geology.

The fresh lime green of peridot is its distinctive signature. Its spring green color also is ideal with sky blue.

Today most peridot is mined, often by hand, by Native Americans on the San Carlos Reservation in Arizona. Peridot found here is beautiful in color but relatively small in size. Faceted peridot from Arizona is rare in sizes above five carats. Fine large peridot are found in Burma and large quantities of peridot are also mined in China. In 1994, an exciting new deposit of fine peridot was discovered in Pakistan, 15,000 feet above sea level in the far west of the Himalaya Mountains in the Pakistanian part of Kashmir.

Peridot, the birthstone for August, is harder than metal but softer than many gemstones. Store peridot jewelry with care to avoid scratches and protect from blows. Because peridot is sensitive to rapid changes in temperature, never have it steam cleaned and avoid ultrasonics. Clean with mild dish soap: use a toothbrush to scrub behind the stone where dust can collect. Your AGTA jeweler will tell you how to best care for your peridot.

REFRACTIVE INDEX 1.635 - 1.673
CLEAVAGE Imperfect



*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!
For more details see the article on "Hardness and Wearability."

Source: Peridot Gemstone Information and Values by International Gem Society


RubyCelebrated in the Bible and in ancient Sanskrit writings as the most precious of all gemstones, rubies have been the prized possession of emperors and kings throughout the ages. Ruby's inner fire has been the inspiration for innumerable legends and myths, and to this day, no red gemstone can compare to its fiery, rich hues. It was believed wearing a fine red ruby bestowed good fortune on its owner - although the owner must have already had good fortune enough to possess such a rare and beautiful gemstone!

Many people associate its brilliant crimson colors with passion and love, making ruby an ideal choice for an engagement ring. Ruby is the red variety of the corundum mineral species, while all other colors of corundum are called Sapphire.

This most sought after gemstone is available in a range of red hues, from purplish and bluish red to orangish red. Ruby is readily available in sizes up to 2 carats, but larger sizes can be obtained. However, in its finest quality, any size ruby can be scare. In readily available small sizes, ruby makes an excellent accent gemstone because of its intense, pure red color

Ruby is mined throughout Southeast Asia. While Thailand and Myanmar (Burma) produce exquisite examples of this gemstone that the ancient Sinhalese people called "Ratnaraj," the King of Gemstones.

Despite all the best efforts of gemstone merchants to use technology to enrich color, fine ruby is still exceptionally rare. After being extracted from the earth, rubies today are commonly heated to high temperatures to maximize the purity and intensity of their red hue. Impurities may also dissolve or become less noticeable after heating. However, heating will only improve the color if the gemstone already contains the chemistry required. Occasionally rubies with small imperfections are permeated with a silicate byproduct of the heating process, which helps to make small fissures less visible. This enhancement, like heating, is permanent and rubies, whether enhanced or not, remain among the most durable of gems.

Today a new method of artificially coloring the surface of paler rubies through the diffusion of beryllium, or a similar element, has made the red of ruby more affordable. Although this method is not yet common, in the future beryllium-diffused rubies may offer an affordable alternative to either untreated or heat-enhanced rubies, which are both much more rare. However, recutting or repolishing may affect the color of some beryllium-diffusion treated rubies. Your AGTA jeweler can tell you how to best care for your ruby. This most sought after gemstone is available in a range of red hues, from purplish and bluish red to orangish red. Ruby is readily available in sizes up to 2 carats, but larger sizes can be obtained. However, in its finest quality, any size ruby can be scare. In readily available small sizes, ruby makes an excellent accent gemstone because of its intense, pure red color

REFRACTIVE INDEX 1.757 - 1.779


ENHANCEMENTS Heat treated. Common. Fractures filled, occasional.

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!
For more details see the article on "Hardness and Wearability."

Source: Ruby Gemstone Information and Values by International Gem Society


SapphireVelvety blue. Liquid blue. Evening-sky blue. Cornflower blue. Sapphire, beloved for centuries as the ultimate blue gemstone. The ancient Persian rulers believed that the earth rested on a giant sapphire and its reflection colored the heavens blue. Indeed, the very name in Latin, "Sapphiru," means blue.

But like the endless colors that appear in the sky, sapphire is also found in many, many other shades besides blue, from the gold of a sunrise, to the fiery reddish-orange of sunset, to the delicate violet of twilight. Sapphire may even resemble the pale white gloaming of an overcast day. These diverse colors are referred to as "fancy" color sapphires.

A gift of a sapphire symbolizes a pledge of trust and loyalty. It is from this tradition that sapphire has long been a popular choice for engagement rings.

One of Nature's most durable gemstones, sapphire shares this quality with its sister, the ruby.

Sapphire is found in many parts of the world, but the most prized sapphires are from Myanmar (Burma), Kashmir and Sri Lanka. The purer the blue of the sapphire, the greater the price the gemstone can command, however, many people find that the darker hues of sapphire can be just as appealing.

Over the centuries, methods have been developed to enhance the purest hues of sapphire. This is now commonly achieved by controlled heating, a technique that not only improves color but also improves clarity. But heating will only improve the color if the gemstone already contains the chemistry required. Heating sapphires is a permanent enhancement, as lasting as the gemstones themselves.

A new method of artificially changing the natural color of a sapphire is diffusion, whereby beryllium or a similar element is diffused into the surface of the gemstone, producing a richer color. Sapphire treated by diffusion is far less costly and much more available than rare fine untreated gems or those successfully heat-treated. Diffused sapphire is available in shades of orange, pinkish orange, yellow and sometimes even blue. Information about diffusion should be provided on the invoice for your jewelry. Recutting or repolishing may affect the color of some diffusion-treated stones. Your AGTA jeweler can tell you how to best care for your sapphire. One of Nature's most durable gemstones, sapphire shares this quality with its sister, the ruby.

REFRACTIVE INDEX 1.757 - 1.779


ENHANCEMENTS Heat treated. Common. Diffusion treatment, (places a thin blue coating on colorless sapphire.) Occasional. Irridation, (turns colorless gems yellow, orange or light blue.) Rare.

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It! For more details see the article on "Hardness and Wearability."

Source: Sapphire Gemstone Information and Values by International Gem Society


SpinelCenturies ago, in Sanskrit writings, spinel was called the daughter of ruby, adored, yet somehow different. The Crown Jewels of Great Britain are graced with spinels and have resided in the regalia of kingdoms throughout history.

Found in Myanmar (Burma) and Sri Lanka, spinel comes in a variety of colors including oranges, pinks, blues, lavenders, mauves and vivid reds. While common in sizes up to 2 carats, larger gemstones can also be acquired.

Spinel is thought to protect the owner from harm, to reconcile differences, and to soothe away sadness. However, the strongest reasons for buying a spinel are its rich, brilliant array of colors and its surprising affordability.

Spinel is a durable gemstone that is perfect for all jewelry uses. It is most often faceted in oval, round or cushion shapes. Clean with mild dish soap: use a toothbrush to scrub behind the stone where dust can collect. Your AGTA jeweler will tell you how to best care for your spinel.

REFRACTIVE INDEX 1.712 - 1.717, normal. Reds may go up to 1.735 and blues to 1.747.
HARDNESS 7.5 - 8



*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!
For more details see the article on "Hardness and Wearability."


TanzaniteTanzanite is an exotic, vivid blue, kissed by purple hues. Legend has it that Tanzanite was first discovered when some brown gemstone crystals lying on the dry earth were caught in a fire set by lightning that swept through the grass-covered hills. The Masai herders driving cattle in the area noticed the beautiful blue color and picked the crystals up, becoming the first tanzanite collectors.

Tanzanite has the beauty, rarity and durability to rival any gemstone. It is the ultimate prize of a gemstone safari. Tanzanite is mined only in Tanzania at the feet of the majestic Mount Kilimanjaro.

One of the most popular blue gemstones available today, tanzanite occurs in a variety of shapes and sizes and also provides a striking assortment of tonal qualities. Rarely pure blue, tanzanite almost always display its signature overtones of purple. In smaller sizes, tanzanite tends toward the lighter tones and the lavender color is more common. While in larger sizes, tanzanite typically displays deeper, richer color.

Tanzanite is so hot, it was the first gemstone added to the birthstone list since 1912 by the American Gem Trade Association.

Virtually every tanzanite is heated to permanently change its color from orange-brown to the spectacular violet-blue color for which this precious gemstone variety is known. Your AGTA jeweler can tell you how to best care for your tanzanite.

REFRACTIVE INDEX 1.692 - 1.700


ENHANCEMENTS Virtually all tanzanite is heat treated

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!
For more details see the article on "Hardness and Wearability."

Source: Tanzanite Gemstone Information and Values by International Gem Society


TopazThe Egyptians said that topaz was colored with the golden glow of the sun god. Legend has it that topaz dispels all enchantment and helps to improve eyesight. The ancient Greeks believed that it had the power to increase strength and make its wearer invisible in times of emergency. Early discoveries from Brazil in rich reddish cognac colors to vivid pinks, were used to grace the jewelry of the 18th and 19th Century Russian Czarinas, hence earning the moniker of "Imperial Topaz."

Topaz sometimes has the amber gold of fine cognac or the blush of a peach, and all the beautiful warm browns and oranges in between. Some rare and exceptional examples are pale pink to a sherry red.

Topaz is found in Brazil, Mexico, Sri Lanka, Africa and China. The birthstone for November, topaz is a talisman for the sign of Sagittarius and is the suggested gift for the 23rd anniversary.

Blue, once the most rare color of topaz, is today the most common, thanks to a stable enhancement process that turns colorless topaz blue. After the raw topaz is extracted from the earth and cut, it is irradiated to brown and then heated to sky blue. This enhancement process is permanent. Due to the popularity of blue topaz, a new treatment process called vapor deposition has been developed to create additional colors of topaz. In this treatment process, similar to those used by opticians and camera makers to make lens coatings, a thin colored film is bonded on the surface of topaz to create dark blue, red, pink, and green colors or rainbow iridescence. These vapor deposition-enhanced topaz colors must be handled with special care, as the coating can be scratched or abraded.

Topaz is a very hard gemstone, with a Mohs hardness of 8, but it can be split with a single sharp blow, a trait it shares with diamond. As a result it should be protected from hard knocks. Clean with mild dish soap; use a toothbrush to scrub behind the stone where dust can collect. Your AGTA jeweler will tell you how to best care for your topaz.

REFRACTIVE INDEX 1.607 - 1.627
CLEAVAGE Perfect one direction


ENHANCEMENTS Pink or Red, may be heat treated. Most blue topaz has been irradiated and heat treated.

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!
For more details see the article on "Hardness and Wearability."

Source: Topaz Gemstone Information and Values by International Gem Society


TourmalineFor centuries tourmalines have adorned the jewels of royalty. The Empress Dowager Tz'u Hsi, the last empress of China, valued the rich pink colors above all other gemstones. The people of ancient Ceylon called tourmaline "turmali," the Sinhalese word for "more colors." Perhaps this is why ancient mystics believed tourmaline could encourage artistic intuition: it has the palette to express every mood.

Vivid reds, hot pinks, verdant greens and blues abound in this marvelous gem variety. Earth tones as varied as a prairie sunset are readily available. Not only does tourmaline occur in a spectacular range of colors, but it also combines those colors in a single gemstone called "bi-color" or "parti-color" tourmaline. One color combination with a pink center and a green outer rim is called "watermelon" tourmaline, and is cut in thin slices similar to its namesake.

Dark blue, blue-green, and green tourmalines are occasionally heated to lighten their color. Red tourmalines, also known as rubellites, and pink varieties are sometimes heated or irradiated to improve their colors. Heat and irradiation color enhancement of tourmalines is permanent.

Occasionally, some tourmalines may have surface-breaking fissures that are filled with resins, with or without hardeners. Care must be observed with these gemstones. Avoid exposing them to harsh abrasives and strong chemical solvents. Your AGTA jeweler will tell you how to best care for your tourmaline.

CHEMISTRY Elbaite, Na(Li,Al)3Al6B3Si6O27(OH)3(OH,F)
REFRACTIVE INDEX 1.603 - 1.655
HARDNESS 7 - 7.5

SPECIAL CARE INSTRUCTIONS Multicolored gems are often weak where the colors meet

ENHANCEMENTS Heat treatment, common on dark gems, otherwise occasional. Irridation, occasional.

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It! For more details see the article on "Hardness and Wearability."

Source: Tourmaline Gemstone Information and Values by International Gem Society


Zircon1 Zircon2In the middle ages, zircon was said to aid sleep, bring prosperity, and promote honor and wisdom in its owner. The name probably comes from the Persian word zargun which means "gold-colored."

The fiery, brilliance of zircon can rival any gemstone. The affordability of its vibrant greens, sky blues, and pleasing earth tones contributes to its growing popularity today.

Zircon is mined in Cambodia, Sri Lanka, Vietnam, Thailand, Kenya, Tanzania and other countries. Because it can be colorless, green, blue, yellow, brown, orange, dark red, and all the colors in between, it is a popular gem for connoisseurs who collect different colors or zircon from different localities.

Zircon is a naturally occurring gemstone and should not be confused with cubic zirconia (a man made synthetic stone). It is highly refractive, which means it is very sparkly if well cut. For this reason, it is Melinda’s favorite colored gemstone. 

REFRACTIVE INDEX Low, 1.78 - 1.85. High 1.92 - 2.01
HARDNESS Low 6 to 7.5 high
SPECIFIC GRAVITY Low 3.9 - 4.1. High 4.65 - 4.80
CLEAVAGE Imperfect

SPECIAL CARE INSTRUCTIONS Facet edges wear off, caution if putting in a ring.

ENHANCEMENTS Virtually all blue zircon is heat treated.

*Wearability is graded as Excellent, Very Good, Good, Poor, and Forget It!
For more details see the article on "Hardness and Wearability."

Source: Zircon Gemstone Information and Values by International Gem Society

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