The GIA Colored Stone Identification Report describes whether the stone is natural or synthetic, identifies the type of gemstone and includes any detectable treatments. This report also contains a detailed description of the gemstone such as cutting style, shape, weight, measurement, and color, and includes a photograph of the gemstone.

The GIA Colored Stone Identification & Origin Report contains all of the information available in the GIA Colored Stone Identification Report along with an opinion on the geographic origin of the stone, if determinable.

GIA has additional services for colored stones including the Monograph™, Portrait™ and Notable Letter for exceptional or museum-quality gemstones. For more information on GIA laboratory services, visit GIA.edu.

A GIA Colored Stone Identification Report can give you peace of mind and ensure that you know exactly what you are buying. With all the treatments and synthetics available today, it takes highly qualified experts to detect them. The experts at GIA have decades of experience and a legacy that is more than 85 years old. All the research, knowledge and dedication of GIA goes into every report we issue.

A symbol of prosperity and longevity.

Alexandrite is a very rare variety of the mineral chrysoberyl that changes color in different light sources. Discovered in 1830 by miners in the Ural Mountains of Russia, these red to green color changing stones resembled the colors of Imperial Russia’s national military. The find was named “alexandrite” after the Emperor Alexander II. Its extraordinary ability to change color takes place when it is viewed under different lighting conditions. For this reason, the color-change phenomenon is called “the alexandrite effect.”

The most-prized alexandrites show a vivid green to bluish green in daylight and fluorescent light, and an intense red to purplish red in incandescent light. They have medium to medium-dark tone and moderately strong saturation. This color change created the phrase, “emerald by day, ruby by night.” A change in hue is what makes this stone unique. Other examples of color change can be green to purple and yellowish green to purplish brown.

Alexandrites tend to contain few inclusions. There’s a dramatic rise in value for clean material with good color change and strong hues. A cat’s-eye phenomenon occurs when needle-like inclusions are oriented parallel.

Some of the finest color alexandrite came from Russia, although today those historical mines produce very little. Alexandrite may be found in Sri Lanka, East Africa, India and Brazil, but fine qualities are exceptionally rare and valuable. Because of its scarcity, especially in larger sizes, alexandrite is one of the more valuable colored gemstones.

Alexandrite is not usually treated except where there are surface-reaching fractures that can be filled.

Believed to quicken intelligence and dispel evil thoughts.

“Amethystos” means “not drunk” in ancient Greek. Because of its wine-like color, early Greek legends associated amethyst with Bacchus, the god of wine. It was believed that wearing amethyst, a quartz, prevented drunkenness. Other legends reflected beliefs that amethyst kept its wearer clear-headed and quick-witted in battle and in business affairs. Fine amethysts have been set in religious jewelry and royal crown jewels for ages. It’s no wonder that fine amethyst adorns the fingers of bishops as well as the coronation regalia of British royalty.

Amethyst is the purple variety of the mineral quartz. It’s the gem most commonly associated with the color purple, even though there are other purple gems such as sapphire and tanzanite. The purple can be cool and bluish, or a reddish purple that’s sometimes referred to as “raspberry.” Amethyst also commonly shows what is called color zoning, which usually consists of angular zones of darker to lighter color.

Much of the faceted amethyst in the market is “eye clean,” meaning it lacks eye-visible inclusions. Any visibly included material is usually cut into cabochons. Gem professionals overlook minor inclusions when the gem is richly colored and of otherwise high quality. Visible inclusions in light-colored gems reduce their value greatly.

Russia was the major amethyst source until the 19th century, when a huge amethyst deposit was found in Brazil. The once scarce purple gem was suddenly in abundance. Today, the two major sources for amethyst are Africa and South America. African mines provide most of the fine color amethyst on the market today.

Heat treatment is the most common technique for improving the color of natural amethyst. It can lighten the color of very dark amethyst but it cannot darken the color of pale amethyst.

Thought to enhance the happiness of marriages.

The name “aquamarine” is derived from two Latin words: aqua, meaning “water,” and marina, meaning “of the sea.” It has been said that the mineral beryl gives the wearer protection against foes in battle or litigation. It makes the wearer unconquerable and amiable, and also quickens the intellect. Today, the gemstone’s hardness, transparency and availability of large stones make it popular with designers, artists and carvers.

Aquamarine is the light green-blue to blue variety of the mineral beryl. It is generally light to medium in tone. Aquamarine’s most valuable color is a vibrant, medium blue to slightly greenish blue.

Aquamarine may occur as large well-formed crystals that are relatively clean, making them particularly valuable to collectors of mineral specimens. Some crystals might contain liquid inclusions, but clarity characteristics are few or absent in most finished gems.

Brazil has been the main source of gem-quality aquamarine since 1811. Most aquamarine mines are located in northeast Minas Gerais, Brazil. The largest aquamarine found in that region was discovered in 1910 and it weighed 244 lbs (110 kg). Another significant producer of aquamarine is Pakistan.

It is standard practice to cut the rough and then heat the fashioned stones. Heat treatment of aquamarine removes the green component and leaves a purer blue color. Nearly all blue aquamarine found in jewelry results from heat treatment of bluish green, greenish yellow or even brownish yellow beryl.

Believed to carry healing properties of the sun, with restorative powers for the body and soul.

The name citrine comes from the French “citron” and Latin “citrus” meaning lemon-colored. Citrine is a variety of quartz, and quartz has been used in jewelry for thousands of years. Naturally colored citrine is rare, and today most citrine quartz is the result of heat treatment of amethyst quartz. Even so, gems from the Victorian era have surfaced, demonstrating that citrine was treasured even in earlier times.

Citrine is the transparent, pale yellow to brownish orange variety of quartz and is quite rare in nature. In the days before modern gemology, its tawny color caused it to be confused with topaz. In the contemporary market, citrine’s most popular shade is an earthy deep brownish or reddish orange. The finest citrine color is a saturated yellow to reddish orange free of brownish tints.

Eye-visible inclusions are not common in citrine but if present they decrease its value.

The top sources for natural citrine are Bolivia, Spain, Madagascar, Mexico and Uruguay. Amethyst that is heat treated to a citrine color is mostly mined in Brazil. In Bolivia, amethyst and citrine colors can occur together in the same crystal. These unique gems are called ametrine.

Most citrine is the result of heating, which converts less valuable shades of purple amethyst to the golden shades of citrine. The saturation of the original amethyst hue will determine the richness of the resulting citrine yellow. Citrine’s attractive color, plus the durability and affordability it shares with most other quartz, make it a top-selling yellow to orange gem

An amulet believed to protect against evil spells.

Emerald has enthralled the elites of civilizations with its stunning beauty and symbolic power for over 6,000 years. The name comes from the old French “esmeralde” through Latin “smaragdus” through Greek “smargdos.” One of the world’s first emerald mines in Egypt was named “Cleopatra’s emerald mine” for her lifetime love affair with the stone. Emeralds from what is now Colombia were part of the plunder when 16th century Spanish explorers invaded the New World. The Spanish, who treasured gold and silver far more than gems, traded emeralds for precious metals. Their trades opened the eyes of European and Asian royalty to emerald’s majesty.

Emerald is the green to bluish green variety of the mineral beryl colored by trace elements of chromium and vanadium. The most desirable emerald colors are bluish green to pure green with strong to vivid color saturation and medium to medium-dark tone. An emerald’s hue, tone and saturation determine its value.

Emeralds are inherently more included than most other gemstones. Eye-clean stones are very rare. Unlike most other stones, visible inclusions are acceptable in emeralds unless they are so numerous as to affect the transparency of the stone. The most prized emeralds are highly transparent with even color distribution and no eye-visible color zoning.

Colombia, Brazil, Zambia and Zimbabwe supply the majority of emeralds on the international market. Colombia produces what many consider to be the highest quality and volume of emeralds. The Colombian emerald has been widely accepted as the world’s most desirable pedigree and its mines remain a prized locality to this day.

Filling surface-reaching fractures or fissures with oil can make them less noticeable, which increases transparency and improves the apparent color of an emerald. Since oil can leak or dry after a period of time, the use of paraffin or resins are sometimes used as a more stable filler.

Thought to possess calming and restorative powers.

The name garnet comes from the medieval Latin “granatus,” meaning pomegranate, in reference to the similarity in color. Thousands of years ago, red garnet necklaces adorned the necks of Egypt’s pharaohs, and were entombed with their mummies as prized possessions for the afterlife. In ancient Rome, signet rings with carved garnets were used as seals to stamp the wax that secured important documents. Centuries later, during Roman scholar Pliny’s time (23 to 79 CE), red garnets were among the most widely traded gems. In the Middle Ages (about 475 to 1450 CE), red garnet was favored by clergy and nobility.

Garnets are a set of closely related minerals that form a group, resulting in gemstones in almost every color. Pyrope and almandine range in color from purple to red. Spessartine is found in a variety of oranges and yellows, while andradite is mostly yellow to green. Grossular has perhaps the widest color range of any garnet species, from colorless through yellow to reddish orange and orangy red, to a strong vibrant green called tsavorite.

Typical garnet clarity depends on garnet type. For example, the red garnets almandine, pyrope and rhodolite, typically do not have eye-visible inclusions. Some of the orange garnets like spessartine and hessonite, often have eye-visible inclusions. Because inclusions affect its clarity, hessonite is not often used in jewelry.

With many different garnet species, the sources for this gem vary. Most tsavorite garnet comes from the East African countries of Tanzania, Kenya and Madagascar. Russia is recognized as the source for high-quality demantoid garnet.

Garnet is rarely treated.

Jadeite is a possession of great luxury in China, where it is believed that a secret virtue of the gem is passed on to its wearer.

The Spanish learned of jadeite jade from the Aztecs of South America, who prized it for its hardness and toughness. Jadeite was discovered in Burma sometime in the 18th century and it quickly became prized by Chinese emperors. They called this new material “Fei Cui,” which referred to the bright green plumage of the kingfisher bird. Often similar in appearance, for a long time no one knew that jadeite jade and nephrite jade were actually two different minerals. In 1863, a French mineralogist named Damour determined that the stones called “Fei Cui” were actually a new mineral, which he named jadeite.

Jadeite is a member of a group of related minerals called pyroxenes. Jadeite occurs in a number of colors including green, lavender, white, orange, brown and yellow. By far the most valuable color is a vivid emerald green, which is often referred to as “imperial jadeite.” Lavender is the second most valuable jadeite color.

The second most important value factor of jadeite is transparency. Semi-transparent jadeite is very rare. A piece that combines semi-transparency with fine green color is exceptionally rare and valuable. Semi-transparent colorless jadeite is also very highly prized.

Jadeite sources include Guatemala, California (U.S.) and the “jade land” of Myanmar (formerly known as Burma). The finest quality jadeite comes from Myanmar.

Treatment of jadeite includes bleaching to remove unwanted brown color followed by polymer impregnation. Artificial dyes and surface waxing can enhance color and luster of lower grade jadeite. Heat treatments are sometimes used to produce orange and reddish colors of jadeite. Jadeite treated in this fashion is called “B” jade.

Nephrite symbolizes a connection between the living and the dead as well as power, wealth and elevated social class.

Discovered in China around 5000 BCE nephrite jade continues to be treasured worldwide. The name jade comes from the Spanish “piedra de ijada,” which means stone of the loins. This is due to the belief that it could cure ailments of the kidneys. The alternate phrase, “piedra de riñones,” translates to “lapis nephriticus” in Latin, which was the root of the word nephrite. The Chinese called this stone “Yu” which could refer to any green stone that possessed the “virtues of Yu.” According to Confucius, these virtues included a compact and fine texture, extreme toughness and high hardness, and a smooth and glossy luster. Due to its interlocking fibrous structure, nephrite is the toughest gemstone known. This toughness is why nephrite was often used to fashion tools.

Nephrite jade is a member of a group of related minerals called amphiboles. Its colors are green, black and a creamy white that the Chinese call “mutton fat.” The “mutton fat” is the most desirable type of nephrite jade and is highly sought after by collectors. The green of nephrite is sometimes referred to as a “spinach” green.

Nephrite is translucent to opaque. It is never transparent or even semi-transparent. The fibrous structure is the reason for nephrite’s extreme toughness and also contributes to its opacity.

Nephrite has been mined in China for thousands of years. It is also found in Russia, Canada and New Zealand. Russia and Canada are the largest suppliers of nephrite in the world market today. New Zealand is also an important source where the Maori refer to it as pounamu. Pounamu is considered treasure and plays a very important role in the Maori culture.

Carvings made of nephrite jade are often rubbed with wax to improve the surface luster. Other than that, nephrite is seldom treated. It is possible for it to be dyed or impregnated but this is rare.

According to Arabic legend, opal was believed to contain lightning.

Writers have compared opal’s color to volcanoes, galaxies and fireworks. Admirers gave extraordinary opals poetic names like Pandora, Light of the World and Empress. In ancient Rome, this gem symbolized love and hope. The Romans gave it a name—opalus—that was synonymous with “precious stone.” Many cultures have credited opal with supernatural origins and powers. The ancient Greeks believed opals gave their owners the gift of prophecy and guarded them from disease. Europeans have long considered the gem a symbol of hope, purity and truth.

Opals display a phenomenon known as play-of-color. When a stone has play-of-color, it is referred to as precious opal. The main categories of precious opal are white, black, boulder, and crystal or water. Fire opal, also known as Mexican opal, sometimes doesn’t show play-of-color.

With an opal, clarity is its degree of transparency and freedom from inclusions. An opal’s clarity can range all the way from completely transparent to opaque. A cloudy or milky background color can sometimes signal a lack of stability. Opals can have fractures and surface blemishes. Matrix, or host rock, along with signs of crazing, a fine network of cracks, have an impact on opal’s durability and value.

Fine opal comes from all over the world. The most significant sources are Australia, Mexico and Ethiopia.

Opals can be treated by impregnation with oil, wax or plastic. Opal doublets or triplets are thin slices of opal glued to a base material and covered with a thin dome of clear quartz. These gems are more resistant to scratching but are considered less valuable. Some opal can be dyed.

Symbol of modesty, chastity and purity.

People have coveted natural pearls as symbols of wealth and status for thousands of years. A Chinese historian recorded the oldest written mention of natural pearls in 2206 BCE. The spherical shape of some pearls led many cultures to associate this gem with the moon. In ancient China, pearls were believed to guarantee protection from fire and fire-breathing dragons. In Europe, they symbolized modesty, chastity and purity.

Pearl bodycolor varies by the type of mollusk it is formed in. Although white pearls are the most traditional, other colors are very popular. The main bodycolor of a pearl is often modified by additional colors called overtones, which are typically pink, green, purple or blue. Some pearls also show the iridescent phenomenon known as orient that adds to the overall color.

Pearls may form in any mollusk. Not all pearls are of the nacreous type commonly seen in jewelry.

Akoya cultured pearls are grown in Japan and China. Leading sources of South Sea cultured pearls are Australia, Indonesia and the Philippines. Tahitian cultured pearls are primarily cultivated around the islands of French Polynesia. China and the United States are leading sources for freshwater cultured pearls.

Pearls may be dyed, coated, bleached, filled or irradiated to either enhance their luster or alter the pearl color. Dyed cultured pearls are usually detectable because they look artificial to the unaided eye. However, dyed pearls of lighter tones can be difficult to detect.

The Egyptians called peridot the “gem of the sun.”

Peridot has always been associated with light. Some believed that it protected its owner from “terrors of the night,” especially when it was set in gold. Others strung the gems on donkey hair and tied them around their left arms to ward off evil spirits. The word peridot comes from the Arabic “faridat,” which means “gem.” Most peridot formed deep inside the earth and was delivered to the surface by volcanoes. Some also came to Earth in meteorites, but this extraterrestrial peridot is extremely rare, and not likely to be seen in a retail jewelry store.

Peridot’s color ranges from yellowish green to greenish yellow. The most favored peridot color is a richly saturated pure grass green without any hint of yellow or brown, which is usually only achieved in gems of 10 ct or larger. Smaller examples tend to show yellowish green hues. Brown undertones lower the value of peridot.

The best-quality peridot has no eye-visible inclusions, with perhaps a few tiny black spots—minute mineral crystals—visible under magnification. Other inclusions common in peridot are reflective, disk-shaped inclusions called “lily pads.”

Peridot is found as irregular nodules (rounded rocks with peridot crystals inside) in some lava flows in the United States, China and Vietnam and, very rarely, as large crystals lining veins or pockets in certain types of solidified molten rock. Sources for the latter include Finland, Pakistan, Myanmar and the island of Zabargad.

Peridot is rarely treated, but might have fractures that can be filled to improve the apparent clarity.

A symbol of wealth and nobility.

Referred to as the king of precious stones, ruby is the red variety of the mineral corundum. The name comes from the Latin “ruber,” meaning red. Red is the color of our most intense emotions—love and anger, passion and fury. It’s associated with objects of power and desire—like fast cars and red roses. Early cultures valued rubies for their similarity to the redness of the blood that flowed through their veins, and believed rubies held the power of life. Ruby retained its importance with the birth of the western world and became one of the most sought-after gems of European royalty and the upper classes. Many medieval Europeans wore rubies to guarantee health, wealth, wisdom and success in love.

The color of ruby is caused by traces of chromium. Color is the most significant factor affecting a ruby’s value. Rubies are available in rich red to dark red and orangey red to purplish red. The most sought-after color by collectors worldwide is a deep red sometimes with a hint of purple, called “pigeon’s blood” in the trade.

Inclusion-free ruby is practically nonexistent so the value varies with how visible the inclusions are. Inclusions can also impact a ruby’s durability, especially if there is a surface-reaching fracture. Typical clarity characteristics include thin mineral inclusions called needles. Rutile needles, or “silk,” can sometimes contribute positively to a gem’s appearance.

The most famous ruby mines are in Myanmar (formerly known as Burma) but rubies can also be found in Vietnam, Mozambique, Madagascar, Kenya, Tajikistan, Afghanistan and Pakistan.

Heat treatment is often used to improve the color or clarity of a ruby. Heat can also cause some fractures to “heal” in certain conditions. Lower quality material may have surface-reaching fractures filled with a glass to decrease their visibility and make the gem more transparent.

A symbol of sincerity and faithfulness.

Sapphire comes from the word “sapheiros,” which means “bright blue stone” in Greek and has been cherished for thousands of years for its color, durability, hardness and luster. Ancient Mediterranean culture honored sapphire above all other gems, and early Buddhists believed in its power for spiritual awareness. One of the world’s most famous blue sapphire engagement rings is the one worn by Catherine, Duchess of Cambridge, which previously belonged to the late Diana, Princess of Wales.

Sapphire and ruby are both members of the mineral species corundum. Corundum is a naturally colorless material, but may have different colors when impurities are present. The rich hues of blue sapphire are universally known but fancy sapphires come in many colors including pink, yellow, purple, colorless, black, green and the rare pinkish orange sapphire referred to in the trade as Padparadscha. Nevertheless, the most preferred and most valuable sapphires are deep color saturations known in the trade as “Royal Blue” and the soft velvety blue called “Cornflower Blue.”

Blue sapphires normally have inclusions, so the lack of visible inclusions can have a positive impact on value. However, in some cases inclusions can increase the value of a sapphire when extremely fine particulate clouds scatter the light, giving the stone a velvety appearance without affecting the transparency.

Kashmir has a long history of mining spectacular blue sapphires that have set records at prestigious auction houses. The velvety “Cornflower Blue” hue and minute inclusions observed in Kashmir sapphire make them the most sought after. Myanmar (formerly known as Burma) is also a highly sought after source of blue sapphire. In the United States, the state of Montana has been a leading producer of both blue and fancy color sapphire.

High temperature treatments are used to improve color or to enhance the clarity of blue sapphire. Diffusing titanium or beryllium into sapphires at high temperatures can achieve a desirable color. Treated sapphire may employ temporary treatments like oiling and dying to hide fractures along with using lead glass to fill pits and cracks for more transparency.

A symbol of power, victory and new hope.

With increasing prominence, a wide color range and reasonable prices, spinel is highly sought after by high-end jewelers. The name spinel comes from the Latin “spina” meaning “thorn,” which refers to the shape of spinel crystals. Spinel has often been mistaken for other gemstones, especially ruby. The most famous 170 ct “Black Prince’s Ruby” given by the Spanish king to the Black Prince of England as a payment for a battle victory, and the 361 ct “Timur Ruby” are actually fine large red spinels. Other large spinels are treasured in the royal collections of India, Russia and other countries.

The color of ruby is caused by traces of chromium. Color is the most significant factor affecting a ruby’s value. Rubies are available in rich red to dark red and orangey red to purplish red. The most sought-after color by collectors worldwide is a deep red sometimes with a hint of purple, called “pigeon’s blood” in the trade.

Inclusion-free ruby is practically nonexistent so the value varies with how visible the inclusions are. Inclusions can also impact a ruby’s durability, especially if there is a surface-reaching fracture. Typical clarity characteristics include thin mineral inclusions called needles. Rutile needles, or “silk,” can sometimes contribute positively to a gem’s appearance.

Fine large spinel crystals, historically referred to as “Balas rubies,” were mined in central and southeast Asia. Key mining locations are Myanmar, Tajikistan, Sri Lanka, Vietnam and Tanzania.

Some spinel might be subjected to heat treatment to improve clarity, but it is a stable treatment. In rare cases, spinel may also be fracture filled to improve its apparent clarity.

A recently discovered gem born in the foothills of Mount Kilimanjaro.

Named by Tiffany & Co. after Tanzania, the country in which it was discovered by a Masai cattle herder in 1967, tanzanite has taken the world by storm and continues to enjoy its growing popularity. Tanzanite is found commercially in only one place on Earth, making it many times rarer than diamonds.

Tanzanite is the blue to bluish purple variety of the mineral zoisite. The most prized is a pure blue color, similar to fine sapphire, or an intense violet-blue. Viewing at different angles, tanzanite’s hue may appear violet. In some exceptional tanzanites, the color is predominately an intense violetish blue with red flashes of pleochroic color coming from within the stone.

Gem-quality tanzanite typically has no eye-visible inclusions. Any inclusions that might pose durability problems—such as fractures—lower tanzanite value greatly. In rare cases, parallel needle-like inclusions may give a stone a cat’s-eye effect.

The only known source in the world is the Merelani Hills near Mount Kilimanjaro in northern Tanzania.

The vast majority of tanzanite is heat treated to transform brownish zoisite into violet or blue tanzanite. The result is permanent. Heat treating brown zoisite converts the brown color to blue or violet hues depending on the orientation of the crystal. Rarely, fracture filling and color coating on the pavilion of a stone gives a desirable but temporary result.

Talisman of wisdom, beauty and longevity.

Topaz served as a symbol of strength among the Greeks. Europeans at the time of the Renaissance believed in its power to destroy curses and dispel anger. “Topaz” comes from the Sanskrit word “tapas” that means “fire.” For centuries, many people in India have believed that topaz worn above the heart assures long life, beauty and intelligence. In the past, a lot of people mistook any yellow colored gemstones for topaz. “Imperial Topaz,” named in honor of the Russian monarchy, is the distinct pinkish orange hue discovered in the 19th century near the Ural Mountains in Russia.

This gemstone features a variety of colors, from colorless, light blue, yellow, orange, pink, violet, brown and, very rarely, red. The element chromium causes natural pink, red and violet to purple colors in topaz. Imperfections at the atomic level in topaz crystal structure can cause yellow, brown and blue color. Colorless topaz is plentiful and often treated to give it a blue color. The rarest, and hence most prized color, is a vivid purplish pink.

Faceted blue topaz is almost always free of eye-visible inclusions. Other more rare colors like orange and pink may show inclusions more often and still be valuable due to the color’s rarity.

The largest topaz mines are in Brazil, Pakistan, Russia and Sri Lanka.

The vast majority of blue topaz seen today is the permanent result of changing the color by irradiation and heating. “Mystic Topaz” has an extraordinary rainbow effect and is made by coating colorless topaz with a thin artificial film placed on the surface by vapor deposition.

Believed to encourage artistic intuition with the palette to express every mood.

Egyptian legend has it that tourmaline gathered all the colors while traveling along the rainbow, thus giving its name, which means “a gem of the rainbow.” The word tourmaline comes from the Sinhalese word “toramalli” meaning “stone with mixed colors” because it often has multiple colors in one crystal, sometimes in extraordinary patterns. Very few gems match tourmaline’s dazzling range of colors, which is why they were easily confused with other gems until the development of modern mineralogy.

Tourmaline’s wide range of colors vary in intensity and tone. Many tourmaline color varieties have inspired their own trade names. The most expensive tourmalines are the highly popular green to violet colors that are often called “electric” or “neon” by the trade. These are known as “Paraíba.” Pink and red colors called “rubellite,” and rich emerald green colors sometimes named “chrome tourmaline,” are also very popular. The name “watermelon tourmaline” is given to a stone

Tourmalines often grow in an environment rich in liquids, and some of those liquids are often captured as inclusions during crystal growth. The most typical inclusions resemble thread-like cavities parallel to the length of the crystal. If cut as a cabochon these may cause a cat’s-eye effect. Pink to red tourmaline often has more visible inclusions than green to blue varieties.

Brazil is a prolific producer of tourmaline. It is also mined in Afghanistan, Kenya, Madagascar, Mozambique, Zimbabwe, Nigeria, Pakistan, Sri Lanka and the United States.

Some tourmalines may be treated to improve their color. The two common treatments are heating and irradiation. Some pink to red colors can be irradiated. Blue to green colors are often heat treated.

Ancient Egyptians called turquoise “mefkat,” which also means “joy” and “delight.”

Turquoise is one of the world’s most ancient gems. Archaeological excavations revealed that the rulers of ancient Egypt adorned themselves with turquoise jewelry, and Chinese artisans carved it more than 3,000 years ago. Turquoise is the national gem of Tibet, and has long been considered a stone that guarantees health, good fortune and protection from evil. The gem’s name comes from the French expression “pierre turquoise,” or “Turkish stone.” The name, which originated in the 13th century, reflects the fact that the material probably first arrived in Europe from Turkish sources.

Turquoise ranges from blue to green in color. The most prized color is an even, intense medium blue. Generally pure saturated blue shades are the most valuable.

Turquoise is semi-translucent to opaque. It might have veins of matrix running through it (matrix is a remnant of its surrounding rock). The most valuable turquoise is an even medium blue with no matrix and the ability to take a polish.

Turquoise is found in only a few places on Earth: dry and barren regions where acidic, copper-rich ground water seeps downward and reacts with minerals. The traditional source for the top color, sometimes described as robin’s egg blue or sky blue, is the Nishapur district of Iran, the country formerly known as Persia. So, quite often, you’ll hear people in the trade call turquoise of this beautiful color “Persian blue,” whether or not it was actually mined in Iran. Another famous producer of high-quality turquoise that rivals the famous Persian material comes from the Sleeping Beauty mine in New Mexico, U.S.

Some turquoise is treated to improve its durability, appearance and polish. Turquoise can be dyed or chemically treated by adding an epoxy or acrylic resin for increased hardness and enhanced color.

Gemstones are treated by various methods to improve their color, transparency or durability. Treatments have been done for thousands of years, although modern technology has increased the kinds of treatments possible. There is nothing inherently wrong with treatments as long as they are fully disclosed to the buyer.

Different treatment methods are applied depending on the type of gemstone:

Filling surface-reaching fractures or cavities with a glass, resin, wax or oil to reduce their visibility and to improve the apparent clarity or durability of gem materials. The filling materials vary from being solids (a glass) to liquids (oils), and in most cases, they are colorless (colored filler materials could be classified as dyes), most notably done to emeralds.

Introducing colored dyes into porous or fractured gems to change their color. Such fractures are sometimes purposely induced by heating and quench crackling the gem so that an otherwise non-porous material can more readily accept the dye.

The surface of a porous gemstone is permeated with a polymer, wax or plastic to give it greater durability and improve its appearance. This treatment is most notably done to jadeite and turquoise.

A chemical used to alter/reduce a component of, or the entire color of, a porous gem. Some gemstones are bleached and then dyed, most notably done to jadeite and pearl.

The exposure of a gem to various elevated temperatures for the purpose of altering its color and/or clarity, or improving its durability. It is potentially done to many gems but most notably to rubies and sapphires.

Exposure of a gem to an artificial source of radiation to change its color. This is sometimes followed by a heat treatment to further modify the color, most notably done to blue topaz.

The penetration of certain elements into the atomic lattice of a gemstone during heat treatment, with the objective of changing its color, most notably done to sapphire.