Alexandrite

     Alexandrite is the birthstone for June. It also is used to commemorate the 45th and 55th wedding anniversaries. Alexandrite has been described as "an Emerald by day and Ruby by night.

    It is one of the few gemstones whose color changes radically under different lights: green, blue-green or pale green in daylight to mauve, violet-red or purplish in incandescent light. A member of the mineral group Chrysoberyl, Alexandrite's color change is due to the differential absorption of different wavelengths of light by trace amounts of chromium. To the layman this means that the red and green are always present but fighting for dominance. If there is more red in the ambient light (i.e. candlelight or incandescent) the reddish nature of Alexandrite prevails. Daylight and most fluorescent light has a greater predominance of blue, hence an Alexandrite will appear bluish green. It is extremely rare to find just the right trace amount of chromium in a natural stone to make this dramatic color change possible, hence the high prices commanded by fine natural Alexandrite.

     Stones over 5 carats are excruciatingly rare, especially 
if the color change is good. The largest known Alexandrite is a gorgeous 66 carat cut stone currently on exhibit at The Smithsonian Institution.

     This gem variety was given the name Alexandrite as it was discovered in 1830 "reportedly" on the same day Czar Alexander II came of age. The first Alexandrites were found in Emerald mines on the right bank of the Takovaya river in the Ural mountains about 57 miles north-east of Sverdlovsk (Ekaterinburg). This location produced stones for a few decades then ran dry and was closed. After that most "Alexs" on the market were from Brazil and Ceylon. Due to recent political changes, some of the old mines have been re-opened and found to produce! The Russian mining is limited to the summer months because of the bitter weather and remote location. As Alexandrite was, at first, exclusive to Russia and displayed their national military colors of green and red, it was long held in very high esteem by Russian aristocrats and royalty.
It is important to note that Brazil produces excellent Alexandrite with a strong color change.

     Although Alexandrite has a high hardness number of 8 ½ , some care must be taken to avoid knocking it against hard surfaces. It should not be exposed to excessive heat (such as a jewelers torch) as that could effect its color change.


TREATMENT: No presently known treatment for Alexandrite.

MOHS HARDNESS: 8 ½

CHEMICAL COMPOSITION: BeAl 2 O 4

REFRACTIVE INDEX: 1.746-1.755 (+/- .004 - .006)
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 3.71-3.73
(The number of times heavier a gemstone is compared to water)

PRINCIPAL SOURCES: Tanzania, Russia (Ural Mountains, Siberia), Brazil and Sri Lanka (Ceylon)

 

Amethyst

      Amethyst is the recognized birthstone for February and the accepted anniversary gemstone for the sixth year of marriage. The transparent purple variety of quartz is one of the most popular of color gems. It was once believed to prevent the wearer from getting drunk, and if the circle of the sun or moon was engraved thereon, it was believed to prevent death from poison. Amethyst was said to have a sobering affect on the wearer-not only those who indulged, but on those over-excited by love's passion as well. The name Amethyst comes from the Greek word amethystos, meaning not drunken. Amethyst is one of the best stones to use for relieving tension and developing patience due to its calming mental effect. Ancient traditions held that genuine Amethysts were ruled by Saturn and focused the planet's energy to protect travelers against danger, clear mental unrest, bring luck to gamblers and prevent intoxication.

      It has symbolized peace, protection and tranquility. Some say it will prevent baldness and improve the complexion, as well as protect from treason and deceit. Because royalty has always adored the color purple, amethysts abound in the ornaments of ancient Greeks and Egyptians, and in the British Crown Jewels.

     Available in shades from light to dark purple, it is relatively hard, fairly brilliant, and overall a good, versatile, wearable stone, available in good supply even in very large sizes (although large sizes with deep color are now becoming scarce). The deepest color, especially with flashes of red against a deep purple background, is referred to as Siberian. The term usually implies a color rather than a locality. Amethysts are sometimes heat treated to intensify the royal purple color (400C to 600C). Jewelers use care to protect Amethysts from excessive heat (i.e., resizing a ring). Amethyst is a durable stone and the color is permanent for all consumer uses. Most Amethysts exhibit zoning of color, especially in large darker stones.

      Amethyst is probably one of the most beautiful stones available at a moderate price, although one must be careful because "fine" amethyst is being produced synthetically today. It frequently exhibits color zoning (often looking like chevrons). Amethyst may fade from heat and strong sunshine.

     As with all gemstones, care should be taken to protect it from scratches and sharp blows.

 

TREATMENT: Sometimes heat treated to lighten and intensify color

MOHS HARDNESS: 7 (a durable stone subject to normal wear and care)

CHEMICAL COMPOSITION: SiO 2

REFRACTIVE INDEX: o=1.544, e=1.553 (very constant)
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 2.651 (very constant)
(The number of times heavier a gemstone is compared to water)

PRINCIPAL SOURCES: Brazil, Uruguay, Zambia, SW Africa, Arizona

AQUAMARINE

     Aquamarine, a universal symbol of youth, hope, and health, is the traditional birthstone for March. It is also the accepted anniversary gem for the 19th year of marriage. (Prior to the fifteenth century it was thought to be the birthstone for those born in October.) In ancient times, the stone was said to aid seafarers; thus it is an excellent gift for sailors or one who takes frequent cruises! To dream of aquamarine signifies the making of new friends; to wear aquamarine earrings brings love and affection. Aquamarine was said to prevent seasickness, quicken the intellect and enhance courage. Long used by royalty, Egyptian amulets of the XII Dynasty (circa 2000 BC) included Aquamarines carved into the forms of animals.

     Aquamarine is a member of the important beryl family, which includes emerald, but aquamarine is less brittle and more durable than emerald. Aquamarine ranges in color from light blue to bluish green to deep blue, which is the most valuable and desirable color. Its blue / blue-green color comes from ferrous iron. The deeper and more saturated the color, the more valuable the stone. The double refraction of light from different angles within the stone causes it to reflect two different colors, blue and green.The ideal color of aquamarine is a refreshing pastel sea blue. Stones with a clear blue color without green or gray are generally the most valuable. It is a very wearable gem, clear and brilliant, and, unlike emerald, is available with excellent clarity even in very large sizes, although these are becoming scarce today.

     One must be careful not to mistake blue topaz for aquamarine. While topaz is an equally beautiful gem, it is usually much less expensive, since it is usually treated to obtain its desirable color. For those who can't afford an aquamarine, however, blue topaz is an excellent alternative - as long as it is properly represented ... and priced. Also, note that many aquamarine-colored synthetic spinels are erroneously sold as aquamarine. As part of the normal finishing process, some aquamarines are heated to remove traces of yellow.

     To maintain the brilliance of this beautiful gemstone, it should be immersed in jewelry cleaner or in lukewarm soapy water and cleaned with a small bristle brush. Do not use a home ultrasonic machine. As with all gemstones, care should be taken to protect it from scratches and sharp blows.

TREATMENT: Commonly heat treated to remove yellow color hence less green tinge.

MOHS HARDNESS: 7.5 to 8 (a fairly hard stone requiring only normal care)

CHEMICAL COMPOSITION: Be 3 Al 2 Si 6 O 18

REFRACTIVE INDEX: o=1.567-1.583 e=1.572-1.590
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 2.68-2.80
(The number of times heavier a gemstone is compared to water)

PRINCIPAL SOURCES: Brazil, Zambia, Nigeria, India, Madagascar, and Ukraine

CITRINE  

     This golden variety of the Quartz Family is often called quartz topaz, citrine topaz, or topaz, all of which are misleading. It is yellow, amber, to amber brown. While a pleasing stone in terms of color, and fairly durable, (equal to it’s sister stone Amethyst), citrine is slightly softer and has less brilliance than precious topaz. It also lacks the subtle color shading, the pinker yellow or pinkish amber shades, which lend to precious topaz a distinctive color difference. Its coloring is due to ferric iron. Its name is from the old French citrin meaning yellow.
 

     Citrine is the traditional gem to give for a thirteenth wedding anniversary, and is often substituted for topaz as the birthstone for November.

     Much citrine is made by heat-treating purple amethyst. Citrine is also much less expensive than precious topaz. It should never be represented as topaz, which technically is "precious" or "imperial" topaz. Citrine is plentiful in all sizes, and can be made into striking jewelry, especially in very large sizes, for a relatively small investment.

TREATMENT: Commonly heat treated (permanent color)

MOHS HARDNESS: 7 (a rather durable stone requiring normal care)

CHEMICAL COMPOSITION: SiO 2

REFRACTIVE INDEX: o=1.544 e= 1.553 (very constant)
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 2.651 (very constant)
(The number of times heavier a gemstone is compared to water)

PRINCIPAL SOURCES: Brazil, Madagascar

 

Diamond   

     Diamond is the birthstone for the month of April. Besides being the most popular gemstone for engagement rings, diamond is the accepted anniversary gem for the 10th and 60th years of marriage.

     The name "diamond" comes from the Greek word "adamas" meaning unconquerable-suggesting the eternity of love. In fact, diamonds have been the traditional symbol of love since ancient Greece.

     Discovered about 2,500 years ago in India, the ancients believed they were splinters from the stars, perhaps crystallized lightening or hardened dewdrops.

     Although diamonds are associated with being a colorless stone, they are occasionally found with a strong, bright color-green, red, pink, blue, canary yellow and amber. These "fancy" colored diamonds are highly prized.

     Occasionally, to improve appearance, diamonds are laser-drilled and, sometimes infilled, where in a foreign substance is used to fill surface cavities or fractures rendering them less visible. Diamonds may also be irradiated and/or heated to induce "fancy" colors. This is usually detectable as a surface only enhancement and reads differently under a spectroscope than the much more rare natural counterpart. Recent highly technical processes incorporate high temperature and high pressure (HTHP) to remove some of the yellow tint that many diamonds possess. Only a small percentage of diamonds are of the necessary chemical type to respond to this treatment. Respectable laboratories, which use this technique, are using lasers to engrave their trademark on the girdles of these stones in a size so small it is only visible under magnification. They are appropriately disclosing this process to informed buyers. Unfortunately, stones are being discovered to have had the engraved trademark removed through recutting / repolishing in an attempt to deceptively remove the proof of enhancement and avoid disclosure. 

     Even though it is the most durable of gemstones, care should be taken to protect a diamond from sharp blows. Household chemicals may discolor or damage the mounting. To clean, you may use a jewelry cleaner, lukewarm soapy water and a small bristle brush, soak in a half-and-half solution of cold water and ammonia for 1/2 hour, or use a home ultrasonic machine with its recommended cleaner. 

EMERALD   

     Emerald is the recommended stone to give for a twentieth or thirty-fifth wedding anniversary and is May's birthstone. It is the green variety of the mineral beryl and one of the most highly prized of all the gems. The name Emerald is from the Greek "smaragdos" (green stone), through the Latin "smaragdus" to Middle English "esmeralde."  Aside from being the birthstone for May, it was historically believed to bestow on its wearer faithfulness and unchanging love. According to legend, the wearing of emerald not only cured a wide range of ailments, including low I.Q., poor eyesight and infertility, but also enabled the wearer to predict the future.  As a revealer of truth, this gem was an enemy of all enchantments and conjurations. It was therefore greatly feared by magicians, who found all their arts of no avail if an Emerald were in their vicinity when they began to weave their spells. However those caught by Cupid's bow found the gemstone useful in learning the truth or falsehood behind the oaths of their lovers. The Emerald has also been worn or utilized in magic for protection. The stone was bound to the left arm with string to guard travelers. They were given to "possessed" persons to exorcise the evil entity within them. Emeralds were employed as an antidote for poisons and for poisoned wounds. To gaze into an Emerald was said to increase sight and relieve eye strain.

     The finest quality emerald has the color of fresh young green grass, an almost pure spectral green, possibly with a very faint tint of blue, as in the "drop of oil" emerald from Colombia, which is considered to be the world's finest. Its fine intense green coloring is due to a trace of chromium or vanadium replacing the aluminum in the beryl structure. Because of the nature of this replacement, almost no Emeralds with intense color are free from inclusions. These inclusions are acceptable as long as they do not take away from the durability or beauty of the stone. Emeralds are often characterized by a garden of included crystals trapped within, known as the "jardin", because under magnification you will see all sorts of lovely patterns resembling foliage in a garden. A flawless, clear emerald is very rare and is usually found in only small sizes. Small to medium sized stones are often faceted in the "step" or emerald cut. The gem is also lovely when cut into a cabochon or dome shape. Sometimes emeralds are even carved.

     Although a hard stone, emerald will chip easily, since it tends to be somewhat brittle, so special care should be given in wearing and handling. Since natural Emerald can contain liquid and gas inclusions, jewelers use care as this gemstone needs to be kept away from any high heat.  Because of emerald's popularity and value, imitations are abundant. Glass (manufactured complete with "flaws"), doublets or triplets such as "aquamarine emeralds" and "Soude' emeralds," which are clever imitations made by inserting layers of green glass (or, more frequently, a green cementing agent) between pieces of aquamarine or quartz "crystal" are often encountered. Also, fine synthetic emeralds have been produced for many years with nearly the same physical and optical properties (color, hardness, brilliance) as genuine emerald. Careful examination by a qualified Gemologist can usually identify the origin as natural or synthetic. Techniques to enhance color and reduce the visibility of flaws are also frequently used. A common practice is to boil the emerald in oil (sometimes tinted green) with the use of a vacuum to force the oil into the openings. Oiling is an enhancement that goes back to early Greek times. This is a widely accepted trade practice, when colorless oils are used and it is properly disclosed, since it is actually good for the stone in light of its fragile nature. Oiling hides some of the whitish flaws, which are actually microscopic cracks, filling the cracks so they be come less visible. The oil becomes an integral part of the emerald, unless it is subjected to some type of degreasing procedure. The development and use of the ultrasonic cleaner has brought to light the extensiveness of this practice. Never clean emeralds in an ultrasonic cleaner or use a steam cleaner.

     All emeralds that are used for jewelry go through the same six-part enhancement process to become the gemstones we know. The steps are sawing, preforming, cutting, polishing, cleaning, and clarity enhancing. Virtually all emeralds require the process of clarity enhancement. This process involves immersing the emerald into a colorless or near-colorless medium. An infinitesimally small amount of the clarity-enhancing medium penetrates open fissures. The volume is so small that it is usually not measurable by weight (typically as little as 1/100,000 of a gram). It should be assumed that every emerald has been processed in this manner unless it has an accompanying laboratory report indicating that there is no evidence of a clarity enhancement medium. Such extraordinarily rare gems command a considerable premium.

     Agents used for clarity enhancement are colorless or near colorless: oils (fair stability), prepolymers and uncatalyzed resins (fair to good stability), paraffin (good stability), and polymers (excellent stability). Using any of the above, except for polymers, to enhance an emerald produces good initial results, but there are some limitations to the effectiveness of these enhancements. Over time, the agents will escape the fissures in the emerald and again reveal the inclusions. Cleaning an emerald using traditional jewelry cleaning products and techniques will also serve to remove these agents from the fissures. The emerald will need to be enhanced, occasionally by “oiling”, to maintain its beauty.

TREATMENT: Commonly oiled to hide flaws. Uncommonly; colored oil is used.

MOHS HARDNESS: 7.5-8 A hard stone, but subject to care because of internal liquid filled inclusions and fractures.

CHEMICAL COMPOSITION: Be 3 Cr 2 Si 6 O 18

REFRACTIVE INDEX: o=1.577, e=1.583 (+/- .017)
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 2.68-2.78
(The number of times heavier a gemstone is compared to water)

PRINCIPAL SOURCES: Colombia, Zambia, Brazil, Afghanistan, and Zimbabwe

GARNET

     Garnet is the accepted birthstone for the month of January. It is also the accepted anniversary gemstone for the second year of marriage. Garnet is not a single mineral but rather a group of similar minerals known as the "Garnet group." The most common deep red Garnets are Almandine/Pyrope, which is what most people mean when they say "Garnet." Pyrope Garnet is found many places in the United States, particularly in Arizona where the pebbles are excavated by ants while digging their holes. The ants then deposit the gems in their refuse mounds, giving this stone the name "ant-hill" Garnet! Garnets are able to withstand enormous heat, up to 1400 degrees Fahrenheit. It derives its name from the Latin granutus , meaning "like a grain" (i.e., a pomegranate seed). Legend holds that Noah hung a large garnet in the ark for illumination. In 1905 a Garnet necklace dating from 3500 BC was found in Egypt around the neck of a young male's mummified body. It reportedly also gives its wearer guidance in the night, protection from nightmares, and according to the Egyptians, is an antidote for snake bites and food poisoning. It was also thought to have a special affinity with the blood.

     Garnet is a hard, durable, often very brilliant stone, available in many colors. You may be surprised to learn that garnets are found in every color except blue, including brilliant green tsavorite garnet, raspberry pink rhodolite garnet, and orange Malaya garnet. The Tsars of Russia favored rare green demantoid garnets, which are more highly dispersive than diamond. Tsavorite is a member of the garnet family and is often mistaken for other (usually more expensive) gems. It is one of the most beautiful, and all but a few would assume it was an emerald of the finest quality. In fact, it is "clearer", more brilliant, and more durable. There is also a rarer green garnet, called demantoid, which costs slightly more than tsavorite but which, although slightly softer, has more fire. These gems offer fine alternatives to the person desiring a lovely green gem who can't afford emerald. While still rare, expensive gems themselves, they are far less expensive than an emerald of comparable quality. Rhodolite Garnet is distinguished from others of the Garnet family by its pink-violet to purple-red color. One of the lesser known Garnets, it as actually a Pyrope-Almandine mix giving it a pleasing rhododendron-like color. The original locality for Rhodolite was Cowee Creek, North Carolina. Stones found there are small (1-2 carats), but new finds in Africa have yielded gems over 25 carats!

     Depending upon the variety, quality, and size, lovely garnets are available for under $20 per carat or more than $3,000 per carat. Garnet also occurs in certain shades of red that have been mistaken for some varieties of ruby. And in yellow it has been confused with precious topaz. Even blue color may occasionally be seen in a very rare color change phenomenon, which some garnets exhibit. It is best known in a deep red variety, sometimes with a brownish cast, but it is commonly found in orangish brown shades, and brilliant wine red shades as well. Garnets offer enough variety in appearance to suit every taste, as well as an outstanding price range to suit every pocketbook.

     As with all gemstones, care should be taken to protect it from scratches, sharp blows, and extreme temperature changes. 

TREATMENT: There is no known treatment for Garnets

MOHS HARDNESS: 7-7.5 (although hard, Garnets abrade easily and should be treated with care) Andradite (Demantoid) 6.5-7

CHEMICAL COMPOSITION: Almandine: Mg 3 Fe 2 Si 3 O 12
Pyrope: Mg 3 Al 2 Si 3 O 12

REFRACTIVE INDEX: n= (approx.)1.75-1.766
(The angle light is bent traveling through a gemstone) Spessartite 1.81, Andradite 1.888

DENSITY (SPECIFIC DENSITY): 3.87-3.95
(The number of times heavier a gemstone is compared to water)

PRINCIPAL SOURCES: Mozambique, Thailand, India, Sri Lanka, Arizona, Brazil

Rhodolite Garnet

TREATMENT: There is no known treatment for Rhodolite Garnets

MOHS HARDNESS: 7-7.5 (durable and well suited for all types of jewelry)

CHEMICAL COMPOSITION: Mg 3 AL 2 Fe 2 Si 3 O 12

REFRACTIVE INDEX: 1.76
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 3.84
(The number of times heavier a gemstone is compared to water)

PRINCIPAL SOURCES: North Carolina, Tanzania, Rhodesia, Madagascar

 Iolite

     Iolite is a relatively plentiful stone offering an excellent substitute to the more expensive blue Sapphire. It is a trichroic (three-colored) gemstone, which means it shows different colors when viewed from different directions -- usually deep blue, violet blue, and light gray. Since the blue color is normally oriented to be viewed from the table, most people consider Iolites to be blue.

     The Vikings found that due to its ability to polarize light, looking through a thin slice of Iolite cancels out most haze and clouds, making the sky appear clearer. This enabled them to navigate safely in the rain. Iolites naturally occur almost exclusively in granite, and have been frequently found in the 1-10 carat range. Also referred to as "Water Sapphire," the name Iolite is from Greek ios color(violet) + lithos (stone).

TREATMENT: There is no known treatment for Iolite

MOHS HARDNESS: 7-7.5 (requiring only normal care)

CHEMICAL COMPOSITION: Mg 2 Al 4 Si 5 O 18

REFRACTIVE INDEX: a=1.522-1.558 b=1.524-1.574 c=1.527-1.578
(The angle light is bent traveling through a gemstone)

SPECIFIC GRAVITY (DENSITY): 2.53-2.78
(The number of times heavier a gemstone is compared to water)

PRINCIPAL SOURCES: India, Sri Lanka, Tanzania, Brazil, USA

Jade

Jade refers to two chemically different stones: jadeite, a silicate of sodium and aluminum, and nephrite, a silicate of calcium and magnesium. Although different, they share many common characteristics. In Europe, the technical characteristics of the two varieties were first published by Damour in 1863; the Chinese were aware of the differences long before.

Jadeite, the rarest and most valuable form of jade, is also known as 'Burmese Jade', (after its traditional and still most important source). It has been in wide use only since the mid-18th century, and today is considered the 'precious' form of jade. Most 'fine jewelry' items of jade consist of jadeite. Jadeite exhibits a wide palette of sometimes vibrant colors, often with translucence. Green is the most valuable color; in particular, a translucent emerald-green is the most prized of all, and is sometimes called 'Imperial Green'. Jadeite is also available in lavender, red, yellow, black and white.

Nephrite, the traditional form of jade, has been used for over 5000 years by many different cultures throughout the world. It is the Chinese, however, that raised the craft of jade carving to an art, and who appreciated it on the deepest levels; the rich mix of mythology and religion in China seemed to find it's highest expression in the virtues of jade. Nephrite colors are subdued, and range from grey to brown to blue-green to black. Translucence is rare. The highest quality comes from Siberia, and sometimes New Zealand or Australia. Taiwan has good nephrite, but the giant of all producers today is British Columbia.


Technical-Characteristics

Jadeite Nephrite
Texture interlocking granular structure
(microcrystalline) interwoven fibrous structure
(cryptocrystalline)
Surface Luster vitreous, sometimes greasy greasy, sometimes vitreous
Fracture Structure granular, possibly splintery splintery, possibly granular
Refractive Index 1.65-1.68 1.60-1.63
Specific Gravity 3.3-3.8 2.9-3.0
Hardness (Mohs) 6.5-7.0 6.0-6.5

Lapis Lazuli 

     Lapis is sometimes used as an alternative December birthstone. Lapis is actually a rock made up of several different minerals, usually lazurite, hauyne, sodalite and nosean, all members of the sodalite group of minerals. Also present are calcite and pyrite in varying percentages. The finest Lapis is considered to be a solid, deep blue with minimal white calcite spots and an attractive sprinkling of golden pyrite. Lapis derives it's name from the Persian word lazhward meaning blue. In ancient times, it was called sapphirus , a name which is now applied to our Sapphire. Powdered Lapis is the basis for the pigment ultramarine, the deep blue color essential to an artist's palette. The production of synthetic ultramarine has fortunately alleviated the need to grind up natural Lapis Lazuli. Lapis has been highly prized as an ornamental stone for over 6000 years. The Lapis mines high above the Kokeha Valley in northeastern Afghanistan were ancient even when visited by Marco Polo in 1271! Perhaps because deep blue Lapis with its flakes of golden Pyrite resembles an evening sky dotted with sparkling stars, it was long regarded as a cure for melancholy (the "blues"), and as an amulet against the spirits of darkness. The cultures of ancient Mesopotamia traded Lapis far and wide, regarding it at least as highly as gold. The Egyptians were equally as fond of the stone and nobles such as King Tutankhamen were interred with great stores of Lapis goods.

     Some care against scratching and chipping should be taken when wearing Lapis. Never clean in an ultrasonic cleaner.

TREATMENT: Commonly dyed 

MOHS HARDNESS: 5-6 (depending on purity)

CHEMICAL COMPOSITION: (Na,Ca) 8 (Al,Si) 12 O 24 (S,So) 4

REFRACTIVE INDEX: 1.50
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 2.7-2.9
(The number of times heavier a gemstone is compared to water)

PRINCIPAL SOURCES: Afghanistan

Onyx 

     Onyx is the variety of agate (cryptocrystaline Quartz) characterized by alternating, parallel bands of black and white. It is traditionally used for the carving of cameos, in which a figure carved in the white layer stands in relief against the black layer. Different names are given to Agate if the white layer alternates with a different color: if red it's called carnelian-onyx, if brown it is known as sardonyx, and if the second layer is one of the pale shades characteristic of common chalcedony it is described as chalcedony-onyx. In order to have a solid piece of black Onyx it must be dyed.

TREATMENT: Frequently dyed black 

MOHS HARDNESS: 7

CHEMICAL COMPOSITION: SiO 2 (Quartz)

REFRACTIVE INDEX: o=1.544 e=1.553
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 2.65-2.91
(The number of times heavier a gemstone is compared to water)

PRINCIPAL SOURCES: Brazil

OPAL

     Opal whose brilliance and vibrant colors resemble the colors of the fall, is certainly appropriate as a birthstone for October, as well as the accepted anniversary gemstone for the 14th year of marriage. The modern name Opal is derived from three ancient sources; the Sanskrit upala , meaning precious stone, the Latin opalus and from the Greek opallios meaning "to see a color change."
     The well-known Roman naturalist Pliny described opal as "made up of the glories of the most precious gems... the gentler fire of the ruby, the rich purple of the amethyst, the sea-green of the emerald, glittering together..." Until recently, no stone has gotten so much "bad publicity" for bringing bad luck as the Opal. Negativity surrounded the stone because of the ease with which the stone could crack, and if given as a lucky or love stone, the splitting was usually taken as a sign of bad luck. Sir Walter Scott fueled its unlucky reputation with his 1800 novel, "Anne of Geierstein," in which the doomed heroine wore an Opal in her hair.
Today, with the understanding of Opal's water content, gem suppliers and miners reject those Opals that tend to crack. Opal has symbolized hope, innocence and purity through the ages. In the Middle Ages, young, fair-haired girls wore opals in their hair to protect its lovely blond color. Medieval writers believed opal could render its wearer invisible when the need arose. It was also said to have a beneficial effect on eyesight. It was thought to banish evil spirits and favor children, the theater, amusements, friendships and feelings.

     When we try to describe the opal, we realize how insufficient the English language is. It is unique among the gems, displaying an array of very brilliant miniature rainbow effects, all mixed up together. Its most outstanding characteristic is this unusual, intense display of many colors flashing out like mini-rainbows called "play of color". This effect is created by opal's formation process, which is very different from that of other gems. Opal is silicon oxide containing variable amounts of water. The color flashes come from natural hydrated silica spheres that create light interference. The water content in an Opal can be anywhere from 1-21 though usually between 3-13. The arrangement of the spheres, which vary in size and pattern, is responsible for the different colors seen. Opal, when not transparent, is usually cut flat or in cabochon, since there is no additional brilliance to be captured by a good faceting job. Color is everything. The more brilliant the color, the more valuable the gem. It is probably more true of opal than any other stone, that the more beautiful the stone and its color, the more it will cost. White opal has a white or light body color with flashes of many colors. Black opal has a black, dark blue, dark green or gray body color with vivid flashes of color such as red, pink and bright green.

     Care should be taken to protect it from scratches, sharp blows, household chemicals, and extreme temperature changes. Due to its high water content it should never be left near any heat or bright light source (i.e., the sun) and should be removed before doing the dishes! To maintain the brilliance of opal, it should be wiped clean with a soft cloth. Do not use a home ultrasonic machine or steam cleaner.

TREATMENT: Opal is not commonly treated, however there exists one treatment of carbon and acid to induce a darker appearance.

MOHS HARDNESS: 5.5 - 6 (a delicate stone requiring gentle handling)

CHEMICAL COMPOSITION: SiO 2 n H 2 O

REFRACTIVE INDEX: n=1.44-1.47
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 1.99-2.25
(The number of times heavier a gemstone is compared to water)

PRINCIPAL SOURCES: Australia, Brazil, Mexico, and United States

 

Pearl

     Pearl is the birthstone for the month of June. It is also the accepted anniversary gemstone for the 3rd and 30th years of marriage. Pearls have been recognized as the emblem of modesty, chastity and purity. They have come to symbolize a happy marriage.

     A pearl is the product of an oyster's defense mechanism. When a foreign irritant is introduced either by man (cultured) or naturally, the oyster immediately surrounds it with layers of a substance called nacre. This forms the exquisite gemstone know as pearl.

     Pearls come in a wide range of colors and overtones. They should be relatively free from skin blemishes. The more perfectly round the shape the better. The higher the luster, or "orient", the more valuable the specimen usually is. And usually the larger the pearl, the greater it’s value.

     Besides the popular round shape, there are stylish mabe (large hemispherical, assembled, cultured pearls) which usually form against the inner shell wall of the oyster, fresh water (elongated in interesting shapes and colors), and South Sea (large cultured pearls 10mm and up from Australia's and Indonesia's waters), to name a few.

     Avoid household chemicals, cosmetics, hair sprays, and perfumes. Don't use ultrasonic cleaners. Wash with mild soap and water and store in a protective chamois pouch or tissue paper.

     Sometimes moonstone is used as an alternative birthstone, by those born in June, since it physically resembles some pearls.

PERIDOT

     Peridot (pronounced with the "T" silent) is one of the few gems which occurs in only one color, green, ranging from lime to olive shades. Peridot is a member of the olivine family, so named because of its olive color. Peridot is the accepted birthstone for August. It is also the accepted anniversary gemstone for the 16th year of marriage. Interestingly, it has also been found in some meteorites, making it one of the few gems known to exist outside of our solar system. Egyptians called the Peridot the "gem of the sun" and counsel priests used it to "keep their minds free from envious thoughts and jealousies concerning the pharaoh's powers" Peridots were favored by pirates, considered powerful amulets against all evil, and when set in gold, were said to protect the wearer from the terrors of the night. They had medicinal uses, too. If fashioned into a chalice from which medicines were drunk, they intensified the effects of the drug. Peridot was also a favorite of the ancients. This lovely transparent yellowish green to deep chartreuse stone was quite a powerful gem. It was considered an aid to friendship and was also believed to free the mind of envious thoughts. Because of its yellowish green color, it was also believed to cure or prevent diseases of the liver and dropsy. It was believed that if worn on the left arm, it would protect the wearer from the evil eye. While not particularly brilliant, the richness of its color is exceptional.

     It comes in shades of yellowish green to darker, purer green colors. It is available in small sizes; larger sizes are becoming scarce. It is not a hard stone and may scratch easily Peridot is often the result of volcanic action. Tiny peridot crystals are sometimes combed from the black sands of Hawaii.

     Peridot is relatively abundant and available in larger sizes. It is found in Burma and the U.S. The most important source of peridot in the world is the San Carlos Apache Indian Reservation near Globe, Arizona, where it is mined primarily by Native Americans. Large sizes are mined in Myanmar (Burma) and peridot is also found in Norway and China.

     Care should be taken to protect peridot from scratches, sharp blows, household chemicals and extreme temperature changes. Do not use a home ultrasonic machine for cleaning.

TREATMENT: There is no known treatment for Peridot

MOHS HARDNESS: 6.5-7 (though fairly durable, avoid high temperatures)

CHEMICAL COMPOSITION: Mg 2 SiO 4 -Fe 2 SiO 4

REFRACTIVE INDEX: a=1.654 b=1.671 c=1.689
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 3.3-3.4
(The number of times heavier a gemstone is compared to water)

RUBY

     Ruby is the accepted birthstone for July. It is also the accepted anniversary gemstone for the 15th and 40th year. Ruby is known as the "Lord of the Gems" because of its rarity and beauty. Derived from the Latin word "ruber", it simply means red. There are so few unflawed Rubies in sizes larger than 5 carats, that anything larger is more valuable than even a Diamond of equal quality and size. The highest quality rubies were said to protect their owners from all kinds of misfortune. A fine ruby assured the owner he would live in harmony with his neighbors. It would protect his stature in life, his home and land. Its protective powers were intensified when set in jewelry, and worn on the left side. Many believed rubies possessed an inner flame which burned eternally.

     Ruby is the red variety of the mineral corundum. Historically, it has been symbolic of love and passion, considered to be an aid to firm friendship, and believed to ensure beauty. Its color ranges from purplish or bluish red to a yellowish red. The finest color is a vivid, almost pure spectral red with a very faint undertone of blue, as seen in Burmese rubies, which are considered the finest. Burmese rubies, which is a term denoting quality and a high degree of fluorescence. The term Burmese has long been synonymous with ideal beauty in a Ruby although such stones are now mined in Vietnam as well as the legendary Ruby mines of Mogok in Burma (now the country of Myanmar). Ruby gets its red coloring from small amounts of chromium. Burmese Rubies do not contain Iron, which kills the natural florescence of Ruby. Therefore a Burmese Ruby will appear more pink and hot candy red in daylight than its poorer, darker cousins from Thailand or Africa. The red color is even more enhanced in low artificial light such as a restaurant where a fine Burmese Ruby will shine like a hot coal while the common darker Thai Rubies "will hide in shame."The ruby is a very brilliant stone and is also a very hard, durable, and wearable stone (a hardness of 9 on Mohs' scale). Because of these characteristics, ruby makes an unusually fine choice for any piece of jewelry. As it is true for other popular gems - the greater the value and demand, the greater the use of techniques to "improve" or to simulate. Again, examples of almost every type of technique can be found: color enhancement, synthesis, substitutes, doublets, triplets, misleading names, etc. Early synthetics were produced in the late 1800’s. The newest synthetic rubies - the Kashan ruby and Chatham ruby - are so very close to their natural counterparts in all properties, that it requires careful observation by a qualified gemologist to distinguish their origin as natural or synthetic.

     As part of the customary fashioning process, virtually all rubies are heated to permanently improve their color and appearance.

     As with all gemstones, care should be taken to protect it from scratches and sharp blows.

     The finest rubies emanate from Burma, having been mined there since ancient times. Other sources include Thailand, Vietnam, Sri Lanka, Kenya, Tanzania, Cambodia, Afghanistan and India.

TREATMENT: Frequently heat treated

MOHS HARDNESS: 9 (a tough and durable stone)

CHEMICAL COMPOSITION: Al 2 O 3

REFRACTIVE INDEX: o=1.768-1.778 e=1.760-1.769
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 3.99-4.1
(The number of times heavier a gemstone is compared to water)

SAPPHIRE

     Sapphire is the September birthstone as well as the accepted anniversary gem for the 5th and 45th years of marriage. The Sapphire derives its name from sapphirus , a Latin term meaning blue. Sapphire owes its deep blue color to a small mixture of iron oxide and traces of titanium oxide. Because of its hardness (corundum is the hardest mineral known next to diamond), Sapphires are one of the best of all jewelry stones. Ancient priests and sorcerers honored sapphire above all gems, for this stone enabled them to interpret oracles and foretell the future. Ancients believed the Ten Commandments were written on a sapphire tablet. Marriage partners put great faith in the stone. If its luster dimmed, one knew his or her spouse had been unfaithful. Sapphire refused to shine when worn by the wicked or impure. Prince Charles chose a blue sapphire for Princess Diana's engagement ring. The choice of sapphire, as a traditional engagement stone in England, has been used for hundreds of years.

     The finest sapphires are considered to be the blue variety - specifically those from Burma and Kashmir, which are closest to the pure spectral blue. Fine, brilliant, deep blue Burmese sapphires will surely dazzle the eye and the pocketbook, as will the Kashmir, which is a fine velvety-toned deep blue. Many today tend to be too dark, but the deep blues can often be treated to lighten the color. The Ceylon sapphires are a very pleasing shade of blue, but are a lighter tone than the Burmese or Kashmir, often on the pastel side. Australian sapphires are frequently seen. These are often a dark blue with a slightly green undertone, as do those from Thailand, and sell for much less per carat. They offer a very affordable alternative to the Burmese, Kashmir, or Ceylon, and can still be very pleasing in their color. Ancient Persians believed the Earth rested on a giant Sapphire and it was the stone's reflection that colored the sky. 

     Sapphires also come in virtually any color, excluding medium to dark red (which would be ruby). These less common colors are known as fancy sapphires. Pink Sapphire gets its red coloring from small amounts of chromium.  While colored Sapphires owe their colors to varying chemical combinations, White Sapphires are pure corundum and therefore colorless. Compared to the cost of blue sapphire and ruby, these stones offer excellent value and real beauty. 

    Techniques have been developed to heat treat natural sapphires to improve the clarity, by removal of a certain type of inclusion called "silk", and to change the color. Some material called "gouda", which is mined in a yellow color, can be cured, by heat, to a more desirable blue. Other heat diffusion processes will enhance the color of the outer "skin" of the sapphire to a deeper blue. In the 1980's the technique for infusing blue (and more recently red) color into the surface of Sapphire was perfected. This process is known as diffusion treatment. The chemicals that cause the blue color in Sapphire (iron oxide and titanium oxide), are induced into the surface layer of Sapphire by heating the stone almost to its melting point (about 1800 C). Natural white Sapphire has become very scarce in the marketplace since "treaters" have consistently outbid gem dealers for the larger sapphire rough. Hence larger natural white sapphire has become more and more valuable and scarce, which might continue as technology advances. While many reject these altered gems as artificial, when properly disclosed, they can be an affordable alternative to the much more rare and expensive unenhanced counterparts.

     As with all gemstones, care should be taken to protect it from scratches and sharp blows.

     Sapphire is found in Sri Lanka (Ceylon), Thailand, Cambodia, Myanmar (Burma), Kashmir, Australia, Nigeria, Kenya, Tanzania, Madascar, China and the U.S.

TREATMENT: Commonly heat treated to intensify or lighten color and improve clarity

MOHS HARDNESS: 9 (a very durable stone)

CHEMICAL COMPOSITION: Al 2 O 3

REFRACTIVE INDEX: e=1.76 o=1.77
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 3.99-4.1 (usually near 4.00)
(The number of times heavier a gemstone is compared to water)

TANZANITE

     This variety of the mineral zoisite was not considered a gem material until 1967, when a beautiful, rich, blue to purple blue, transparent variety was found in Tanzania (hence tanzanite). The name Tanzanite was given to this stone by Tiffany & Co. in 1969 as a trade name and has stuck ever since. It is usually found in veins of granite schist with calcite, sulfur, quartz, and green garnet. Tanzanite can possess a rich, sapphire blue color (possibly with some violet red or greenish yellow flashes). This lovely gem can cost many thousands of dollars per carat today in larger sizes. But one must be cautious. It is relatively soft, so we do not recommend tanzanite for rings (unless it's set in a very protected setting) or for everyday wear in which it would be exposed to knocks and other abuse. One must also be aware that a very inexpensive, dull, brownish zoisite can become a beautiful, expensive tanzanite after heat treatment.

TREATMENT: Commonly heat treated (permanent color)

MOHS HARDNESS: 6.5 (though fairly durable, as a result of the heating process, they become more brittle. It is recommended to avoid cleaning in an ultrasonic cleaner)

CHEMICAL COMPOSITION: Ca 2 Al 3 Si 3 O 12 (OH)

REFRACTIVE INDEX: o=1.685-1.705, r=1.688-1.710, q=1.697-1.725
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY) : 3.15-3.38
(The number of times heavier a gemstone is compared to water)

TOPAZ

     Topaz is the accepted birthstone for November. Blue topaz is the accepted anniversary gemstone for the 4th year; Imperial topaz for the 23rd year of marriage. Citrine is often used an alternative to topaz because it appears in many of the same colors as topaz. Unlike topaz, citrine is readily available and inexpensive even in large sizes. In ancient times just about any stone was likely to be called a Topaz. It is thought that the word Topaz is either derived from the Sanskrit word tapas meaning fire or topazioz the Greek word meaning to guess. It has been considered as a symbol of love and affection. The lore, magic and romance of topaz goes back many thousands of years. It holds the distinction of being the gemstone with the widest range of curative powers. The Greeks felt it gave them strength. In addition, it supposedly cooled tempers, restored sanity, cured asthma, relieved insomnia and even warded off sudden death. Topaz is said to make its wearer invisible in time of emergency. It proved the loyalty of associates by changing color in the presence of poison.

     The true topaz is infrequently seen in jewelry stores. Unfortunately, most people know only the quartz (citrine) topaz, or glass. In the past almost any yellow stone was called topaz. Topaz occurs not only in the transparent yellow, yellow brown, orangy brown, and pinkish brown colors most popularly associated with it, but also in a very light to medium red (now found naturally in fair supply, although many are produced through heat treatment), very light to light blue (also often the result of treatment, although it does occur naturally on a fairly wide scale), very light green, light greenish yellow, violet, and colorless. Orange-red "Imperial" topaz and pink colors are rare and most valuable. Topaz is a hard, brilliant stone with a fine color range, but it is much more rare and much more expensive than the stones commonly substituted for topaz. Blue topaz has become very popular in recent years. Most of it has been heat treated and/or irradiated to "cure" the color. It closely resembles the finest aquamarine (which is very expensive today) and offers a very attractive, and much more affordable alternative. Silver Topaz is an eye-clean, colorless, and brilliantly sparkling stone. With its very affordable price, it offers an inexpensive alternative to the Diamond or white Sapphire. Sky Blue Topaz, with its light to medium sky blue coloring, has proven to be an excellent substitute for the more expensive Aquamarine.  London Blue Topaz is the darkest of the blue Topazes and makes an excellent substitute for the more costly blue Sapphire. Super Blue Topaz is a trade name referring to an intense vibrant blue Topaz. It is also known as Swiss Blue and Max Blue.

     Topaz is found mainly in Brazil, Nigeria, Sri Lanka, Mexico, Pakistan, USA and China.

TREATMENT: Neutron irradiation and heat treatment (permanent color)

MOHS HARDNESS: 8 (durable stone but prone to chipping)

CHEMICAL COMPOSITION: A l2 (F,OH) 2 SiO 4

REFRACTIVE INDEX: a=1.606-1.629 b=1.609-1.631 c=1.616-1.638
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 3.56-3.57
(The number of times heavier a gemstone is compared to water)

TOURMALINE

     Sometimes pink tourmaline is used as a birthstone for October. It takes its name from the Singhalese word turmamali meaning "mixed precious stones" because they were often confused with other gems.Tourmaline spans the color spectrum from red to violet and in every tone. It also occurs in color combinations in one stone (bi-colored or tri-colored), which accounts for its popularity. The fascinating "watermelon" tourmaline looks just like the inside of a watermelon-red in the center surrounded by a green "rind." 

     Tourmaline is a fairly hard, durable, brilliant, and very wearable stone with a wide choice of colors. It is not as fragile as opal, and is sometimes selected by those who prefer faceted stones. It is a gem of modern times, but nonetheless has found its way to the list of birthstones. Perhaps this honor results from tourmaline's versatility and broad color range. Or perhaps to the fact that red-and-green tourmaline, in which the red and green occur side by side in the same stone, is reminiscent of the turning of October leaves. 

     Tourmalines have an interesting pyroelectricity property -- on gentle heating (100 o C) the crystal develops a positive charge on one end and a negative charge on the other. This charge is strong enough to enable the stone to attract or repel light-weight substances such as ash or dust. Benjamin Franklin used to carry a Tourmaline to demonstrate this magnetic quality. 

TREATMENT: Often heat treated and/or irradiated to improve color. These process are permanent.

MOHS HARDNESS: 7-7.5 (a fairly tough stone suitable for most jewelry)

CHEMICAL COMPOSITION: NaLi 3 Al 6 B 3 Si 6 O 27 (OH) 3 (OH,F)

REFRACTIVE INDEX: o=1.640-1.655 e=1.625-1.650
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 3.01-3.06
(The number of times heavier a gemstone is compared to water)

PRINCIPAL SOURCES: Brazil, Africa, USA

Turquoise

     Turquoise is the accepted birthstone for December and is the accepted anniversary gemstone for the 11th year of marriage. Turquoise is formed by the action of percolating groundwater in aluminous rocks where copper is present, as in the vicinity of copper deposits. The name means "Turkish stone" because the trade route that brought it to Europe used to come via Turkey. Some say that in the thirteenth century, Turquoise was named in the mistaken belief that it came from Turkey. Others say that the name comes from the Persian word for Turquoise, firouze, since Persia has been a major source of this gemstone for thousands of years. In any case, the blue of this gemstone is so vivid and distinct that it has given its name to the color! The best qualities are found in northeast Iran (Persian turquoise). However, the United States southwest is now the world leader in production.     

     Turquoise has been a treasured gemstone around the world for thousands of years. It was used for beads by the Egyptians as early as 5500 BC. The deposits in Sinai were already worked out by 4,000 BC. In many cultures, Turquoise is regarded as a harbinger of good fortune, success and health. Aztecs and Egyptians considered it a symbol of prosperity. In India, one was to wear a Turquoise on the little finger and look at the gem after seeing the new moon to gain great wealth. According to American Indians, the stone brought together the spirits of sea and sky to bless warriors and hunters; a Turquoise arrowhead assured accurate aim. A Navajo belief is that a piece of Turquoise cast into a river will cause rainfall. Ancient doctors exploited the stone's medicinal potential by making it into paste to treat ailments of the hip. The Egyptians also mounted Turquoise in Silver to treat eyes suffering from cataracts.

     From the thirteenth century comes the belief that Turquoise possessed the power to protect the wearer from injury by falling, especially from horseback; later, this was extended to cover falls from buildings or over a precipice. Turks often attached Turquoise to the bridles of their horses believing that it rendered the horse more sure-footed. As the horse was often regarded as a symbol of the sun in its rapid course through the heavens, the sky-blue color of Turquoise may have caused it to be associated in some way with the horse. During the 16th century, turquoise was used as currency, by the Southwest Indians. They believed the gemstone could bring spoils to the warrior, animals to the hunter, and happiness and good fortune to all. In Europe, Turquoise seems to have been worn almost exclusively by men at the beginning of the 17th century and was so highly regarded by them that no man considered his hand to be well adorned unless he wore a fine Turquoise.
 At that time the stone was used for jewelry, amulets and in the preparation of cosmetics. 

     Colors in turquoise range from sky blue (most desirable color) to blue green and apple green.In general the bluer the blue, the more highly valued. A clean, even texture without mottling or veins is also preferred, however some people like their Turquoise with veins, or "spiderwebs", which sets off the color.  Although large quantities of beautiful turquoise which have not been color enhanced are available, today's turquoise is commonly stabilized with plastic to improve its color and durability. Chalky varieties of turquoise are normally impregnated with oil or wax to enhance color. This color change may not be permanent. 

     Care should be taken to protect it from scratches, sharp blows, hot water, and household chemicals. Do not use a home ultrasonic machine.

     Blue topaz and blue zircon have become a popular alternatives in recent years for those who prefer faceted stones.

TREATMENT: Commonly stabilized with paraffin wax or resin; sometimes dyed 

MOHS HARDNESS: 5-6

CHEMICAL COMPOSITION: CuAl 6 (PO 4 )4 (OH) 8 5H 2 O

REFRACTIVE INDEX: 1.62
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 2.84
(The number of times heavier a gemstone is compared to water)

PRINCIPAL SOURCES: American Southwest, Iran, Central Asia

Zircon

     Zircon is a genuine gemstone not to be confused with the man-made cubic zirconia. This gem has a very high birefringence (splits light into two rays) which makes the back facets appear double when looking through the stone. Zircon is more strongly refractive than any other precious stone with the only exception of the Diamond. It has derived its ancient name from the Arabic zargun, which is from the Persian zar (gold) plus gun (color). Zircon is an accessory mineral in various types of magmatic, sedimentary and metamorphosed rocks. A remarkable property of Zircon is that its refractive index rises when its temperature is raised.

TREATMENT: Heat treated (permanent color)

MOHS HARDNESS: 6.5-7.5 (a brittle stone, it does well in a protective mounting)

CHEMICAL COMPOSITION: ZrSiO 4 +Fe, U, Th, Hf

REFRACTIVE INDEX: o=1.92-1.94 (often 1.925) e=1.97-2.01 (often 1.984)
(The angle light is bent traveling through a gemstone)

DENSITY (SPECIFIC GRAVITY): 4.6-4.8 (usually about 4.70)
(The number of times heavier a gemstones is compared to water)

PRINCIPAL SOURCES: Cambodia, Thailand, Sri Lanka