Gemstone
Directory
I would like to thank my unknown source of this table, I downloaded most of it several years ago
without keeping the source's information. I have added and edited the original, but the bulk was
coppied directly from an
unknown source. THANK YOU!
Turquoise is out of alphabetic order and will take you to off this table and to my Turquoise
info page.
Colors: Most colors
Refractive Index: 1.54 - 1.55
Durability: Fairly tough, can crack or chip
S.G.: 2.65 - 2.91
Material: Quartz
Treatment: Dyeing
Hardness: 7
Availability: Abundant
Localities:
Price: Low
Common Shapes: Cabochons, beads & cameos
Interesting Facts
Said by the ancients to render the wearer invisible, Agate has been admired by humanity for thousands of years. Its beauty and durability have prompted man to use it in both practical and ornamental forms.
One of the more outlandish uses is binding an Agate to each horn of your oxen to ensure a good harvest. The danger here is that your appropriately agated beasts of burden may then become invisible and a little hard to find.
In 1709 a Brazilian priest planned to use agates as antigravity devices on an air ship he had designed.
Agate is believed to cure insomnia, ensure pleasant dreams, protect from danger, promote strength, healing and a bold heart. Wearers become temperate, continent and cautious. Agate is a cooling stone; it reduces fever, quenches thirst, quiets the pulse and heart throbs and ensures good health and a long and prosperous life.
Agate is formed in a unique way and many fossils are actually agatized material that has replaced the original organic substance. For example, petrified wood is fossilized wood that has had its organic matter replaced by agate.
The main conditions necessary for agate formation are the presence of silica from devitrified volcanic ash, water from rainfall or ground sources, manganese, iron and other mineral oxides that form the bands and inclusions.
Characteristics
Agate is a fine-grained fibrous variety of Chalcedony Quartz and comes in many different forms ranging from transparent to opaque. Varieties include Blue, Blue Lace, Crazy Lace, Green, Indian, Moss, Tree, and Wood. Most popular are: Blue lace agate which has swirly white bands in a blue background; moss agate is so named for its moss-like pattern; fire agate is a brown-bodied stone containing yellow, green, and orange spots, with an iridescent shimmer like opal.
Evaluation
As there are so many varieties of
agate, it is largely up to the buyer to determine its value. Most agate is in
the low price range but some picture stones, carvings and unique pieces may
command higher prices. The popularity of fire agate has increased in recent
years, as has its price.
Ocean Jasper®
New Rock Discovery!
New discoveries brought to market are usually new deposits of an already known material. It is rare indeed that a really new material is found. Ocean Jasper fits the description of a truly new jasper.
Rhyolite is an igneous rock, rich in silica. As it cools, sometimes the silica starts to precipitate out of the magma, forming little spherical balls. This type of formation is easily recognizable in the aforementioned jaspers. If these balls or "globs" of silica-rich magma are allowed to grow larger before the whole mass becomes solid, they can crack and shrink forming what later may become Thundereggs.
Ocean Jasper has a typical rhyolite formation except that the entire mass has somehow been converted to pure silica (agate, jasper, quartz). The descriptions "silicated rhyolite", petrified rhyolite, or agatized rhyolite are non-sensical but take on a generally understandable meaning when viewing this rock. To my knowledge, there has never been a material like this available before.
The Name -- Ocean Jasper®
The material is characterized as an orbicular jasper. That is because whenever a rhyolite has been found with enough silica in it to be polished, it has been sold as a jasper. Thus the rhyolite patterns have been associated with the word "jasper".
Ocean Jasper is an agate by the standard definition (agate being translucent and jasper being opaque). Ocean Jasper is rarely opaque. It was decided to call the material a jasper because rhyolitic patterns have been associated with the jasper category in the past and because "jasper" is listed as the mineral resource in the mining claims owned by Madagascar Minerals.
The word "Ocean" comes mainly from the location at the edge of the sea, along the northwest coast of Madagascar where the deposit was found. The forms in the rock itself are also suggestive of the bubbling surf of the sea.
Go back to Gem Table
Alexandrite
Colors: Green & violet red color change
Refractive Index: 1.74 - 1.76
Durability: Tough
S.G.: 3.5 - 3.8
Material:Chrysoberyl
Treatment: None
Hardness: 8.5
Availability: Very rare
Localities:
Price: Low/moderate to very expensive
Common Shapes: Ovals, rounds & cushions
Interesting Facts
Alexandrite is one of the worlds
most exotic and rare gemstones. By day, it resembles the green fire of
emeralds, and by night, it takes on the glowing red luster of rubies.
Alexandrite was first discovered around 1830 on the
birthday of Czar Alexander of
The worlds major source of
alexandrite is in the state of Minas Gerias,
Characteristics
Color change is not unique to only alexandrite; however, the extremity of the color change in this gemstone surpasses all others. When alexandrite is viewed under daylight or fluorescent light, its color is that of medium to bluish green; however, when it is observed under incandescent light, its color is that of violet red. Alexandrite is quite tough. Its hardness is only transcended by those ofcorundum-based gemstones, such as rubies, sapphires and of course diamonds. Alexandrite can also occur in a cats-eye form, but it is exceptionally rare. In its finest quality, the gemstone should be semi-transparent with a sharp exhibition of the white eye.
Evaluation
The degree of color change is the first and most important consideration when evaluating the value of alexandrines. Low quality stones will present a less dramatic change of color, partially retaining some of the green color or appearing brown under incandescent light. The evaluation of alexandrite should be performed in a dark room under a single light source (i.e. a candle or a light bulb).
Go back to Gem Table
Amethyst
Colors: Pale to dark violet
Refractive Index: 1.54 - 1.55
Durability: Fairly tough
S.G.: 2.65 - 2.91
Material: Quartz
Treatment: Heating
Hardness: 7
Availability: Abundant in many sizes
Localities:
Price: Low
Common Shapes: Everything is possible
Interesting Facts
Amethyst is one of the most common gemstones available and has been popular since Pre-Roman times. The wine-loving Greeks believed that amethyst prevented intoxication while medieval European soldiers wore amethyst amulets as protection in battle.
Amethyst is actually a form of Quartz one of the most common substances on earth. Tiny amounts of iron and aluminum turn ordinary clear quartz into amethyst.
All forms of quartz (including amethyst) are piezoelectric, making for important applications in electronics. Tourmaline is the only other gemstone that possesses this property.
The term "Siberian"
amethyst refers to a high grade of stone that is no longer
commercially produced. Most of the high-grade amethyst mined today is in
Characteristics
Amethyst ranges from pale to dark violet. The finest qualities of amethyst are a medium dark violet with a strong secondary red color. Darker shades of amethyst may display slight color fluctuations under different light sources.
Amethyst of all qualities is available in all sizes and shapes. Light amethyst will be very low in per carat prices while even the finest qualities are still very reasonably priced. Darker amethyst of any size will have color zoning. This may not be visible without extensive examination. Often the zoning consists of areas of red violet and areas of blue violet, this combination can enrich the appearance of the stone. However, sometimes the zoning is easily visible and detracts from the beauty of the stone. If the zoning is unsightly the value is lessened.
Evaluation
Amethyst is the most expensive variety of quartz. Uniformity of color and intense, deep color commands the highest price. Any color zoning or inclusions diminish the price. The highest grade will flash red and pink throughout the gem.
Go back to Gem Table
Aquamarine
Colors:Blue
Refractive Index: 1.56 - 1.59
Durability: Slightly fragile to tough
S.G.: 2.67 - 2.84
Material: Beryl
Treatment: Heating
Hardness: 7.5 8
Availability: A variety of sizes
Localities:
Price: Low to very expensive
Common Shapes: Emerald cuts, ovals & cushions
Interesting Facts
For many centuries, oceanic energy was believed to be contained within the delicate semblance of aquamarines. When amulets made of this precious gem were worn, sailors believed that unmatched bravery would be instilled into their souls, giving them the power to overcome even the most powerful storm.
Characteristics
Aquamarines are often eye-clean, and any inclusions within this blue gemstone can easily be seen. A variety of sizes are readily available, and as the size increases, the color of aquamarines tends to intensify.
Evaluation
The intensity of color and the clarity of the stone are the most important criteria when evaluating this captivating blue stone. Deep blue aquamarines are rare and command higher prices in the worlds gemstone markets.
Go back to Gem Table
Carnelian
Colors:
Refractive Index: 1.54 - 1.55
Durability: Fairly tough
S.G.: 2.65 - 2.91
Material: Quartz. Silicon Dioxide with Iron impurities
Treatment: Heating, dyeing
Hardness: 6.5 - 7
Availability: Abundant in many sizes
Localities:
Price: Low
Common Shapes: Beads, cabochons & cameos
Interesting Facts
Fit for a queen. An
ancient Sumerian queen at that! Carnelian has been an important gem in
nearly every great civilization the world has ever seen. From the royalty of
Also known as Sadoine or Mecca Stone and sometimes spelt Cornelian, the name Carnelian is derived from Carne, the Latin for flesh, due to the stones coloring.
A deeply religious stone, Carnelian
was used by the Egyptian goddess Isis to protect the dead on their journey
through the afterlife; it is the symbol of the Apostle Philip; was one of the
stones on Aarons breast plate of judgment (Exodus: xxviii, 15-30); and
Muhammads seal was an engraved Carnelian set in a silver ring. To this day
Buddhists in
Carnelian is recommended for those with bad memories, creative blocks, befuddled minds, weak voices and a lack of courage. It is said to be beneficial in treating impotence, infertility, insomnia, menstrual cramps, neuralgia, rheumatism, asthma, bad blood,lethargy, digestive problems, and skin conditions like acne and psoriasis in both humans and animals. Carnelian also helps hotheaded people overcome anger and establish self-control, and it even protects the wearer from envy and falling objects.
Carnelian is the national gemstone
for
Characteristics
Carnelian is a translucent orange to red variety of chalcedony. The red tints are caused by iron oxide impurities. It is most commonly made into beads, cabochons, and carvings.
Evaluation
As carnelian is fairly common, it is an inexpensive gem. The best carnelian is translucent. Some carnelian will be dyed. Carnelian is often carved and the quality of carving is a key issue in determining price.
Go back to Gem Table
Chrysoberyl
Colors: Yellow, yellowish green, green, brown, violetish red & greenish-blue color change
Refractive Index: 1.74 - 1.76
Durability: Tough
S.G.: 3.5 - 3.8
Material: Beryllium Aluminum Oxide
Treatment: None known
Hardness: 8.5
Availability: Alexandrite & cats eye very rare. Yellows & greens available
Localities:
Price: Low/moderate to very expensive
Common Shapes: Ovals, rounds & cushions
Interesting Facts
Encompassing such unusual features as color-change and chatoyancy, the chrysoberyl family is an enigmatic category of gemstones ranging from very inexpensive to top-drawer prices.
There are three principal varieties of chrysoberyl:
Alexandrite and cymophane (cats eye) are well known and among the most expensive of all gemstones. Ordinary faceted chrysoberyl is equally rare and beautiful, yet is one of the least expensive stones. All varieties are exceptionally tough, producing some extremely durable gems.
The name chrysoberyl is derived from the Greek for golden (chryso) and green gemstone (beryl). The color ranges from yellow to green to brown. When cut, ordinary chrysoberyl is an extremely brilliant stone, ideal for everyday wear and it is anticipated that it will be one of the next new products to become fashionable in the jewelry industry in the near future.
Chrysoberyl is said to assist in striving for excellence, bring peace of mind and increase self-confidence. It also promotes kindness, generosity, benevolence, hope, optimism, renewal, new beginnings, compassion and forgiveness. This stone expresses springtime, youth and innocence.
Chrysoberyl is said to enhance the healing properties of other stones, and to treat disorders of the pancreas, liver and kidneys.
Characterisitics
Ordinary transparent chrysoberyl is most often yellow, yellowish green, or brown in color. The color in yellow chrysoberyl is due to iron (Fe+3) impurities. When well cut, it produces bright, durable gems that, while not often seen in jewelry, are attractive and relatively affordable.
Cats-eye chrysoberyl is a
translucent gem ranging in color from a honey yellow or honey brown to
yellowish green to an apple green. It is known for its
reflected light effect called chatoyancy. This is achieved
by cutting stones that have very small, parallel silk inclusions into
cabochons (dome shapes, not faceted). As the gem is rotated,
it exhibits a distinct, silvery white line across its dome that seems to open
and close like a cats eye.
Evaluation
The most desired stones are brilliant yellows, greens and occasionally oranges. The browner a chrysoberyl is, the less valuable.
Faceted stones over 10 carats are rare, over 20 carats extremely hard to obtain, and clean stones over 30 carats are museum pieces.
Fine cat's-eyes may be yellow, yellowish green, or golden brown. In the finest qualities, the gems will be semi-transparent and they will exhibit a sharp white eye. As you turn the stone around, the eye will move. The best cat's-eyes also exhibit a "milk and honey effect," when the stone is rotated, one side of the stone appears transparent, as the other side takes on a creamy appearance. In large cat's-eyes, the milk and honey effect is an important consideration in valuing the stone. Cat's-eyes are always cut into cabochons.
Go back to Gem Table
Citrine
Colors: Yellow, orange, red
Refractive Index: 1.54 - 1.55
Durability: Fairly tough
S.G.: 2.65 - 2.91
Material: Quartz.
Treatment: Presume heating
Hardness: 7
Availability: Abundant in many sizes
Localities:
Price: Low
Common Shapes: Everything is possible
Interesting Facts
One of the most affordable gemstones on the market, citrine is a golden yellow form of quartz which takes its name from "citron," the French for lemon.
In former times citrine was used as a protective talisman against the plague, bad skin and evil thoughts, and as a charm against snakebites and other venomous reptiles. It is also believed to symbolize happiness, aid digestion, remove toxins from the body, and be useful in the treatment of depression, constipation and diabetes.
Citrine is one of the accepted
birthstones for November, as well as the anniversary gemstone for the 13th year
of marriage. It is found mainly in
Characteristics
Citrine does appear naturally but
most commercial citrine is the result of heating amethyst. Colors range from
pale yellow to yellowish-brown and
Since most citrine starts out as
amethyst that is heated to turn its color to gold,
citrine jewelry should be kept away from prolonged exposure to strong light or
heat. With this precaution, citrine jewelry will last for many generations.
Evaluation
Citrine is readily available, very affordable in large sizes and stands up well to daily wear. Citrine can be easily confused with topaz and has even been called topaz quartz. This is incorrect and should be watched out for.
Go back to Gem Table
Diamond
Colors: Clear, yellow, brown, pink, blue, green, lavender, orange & red
Refractive Index:\2.42
Durability: Tough but has perfect cleavage, protect from blows
S.G.:3.52
Material: Carbon
Treatment: None common. Laser drilling and filling (fracture filling), irradiation and heating to produce fancy colors
Hardness: 10
Availability: Strong supply in colorless to tinted yellow in stones up to five carats
Localities:
Price: Expensive
Common Shapes: Round, marquise, pear, oval, heart,emerald,radiant,princess,trilliant & more
Interesting Facts
The hardest, rarest, densest natural
substance known to man, diamonds have been a source of fascination (and
misinformation) since 800 BC when they were first presented to
royalty in
As bewitching as diamonds are they
have produced more than their fair share of myths over the centuries. Theyve
been attributed with increasing potency,preventing
lechery, driving away nightmares, counteracting poison, warding off evil,
protection from wild beasts, healing sickness and (naturally) attracting good
fortune. Theres also the lie detector myth: that
diamonds will darken in the presence of a guilty person and brighten in the
company of an innocent one; and the magical reproduction legend: that diamonds
sprinkled with morning dew and left in the dark can reproduce offspring! If
only!
Despite these fanciful ideas some of the amazingly real attributes of diamonds include: their age the first diamond deposits were brought to the surface of the earth approximately 2.5 billion years ago while the most recent deposits are roughly 50 million years old; their hardness diamonds are so hard they can only be polished by other diamonds; rarity more than 250 tons of ore need to be blasted, crushed and processed to yield one carat of rough diamond and of that rough, only 20% is suitable for gem cutting; density diamond is so dense that it actually slows down light to less than half its normal speed - 80,000 miles per second;
fluorescence if youre in a nightclub and someones ears or fingers start to glow then diamonds are most likely the culprit, 30-40% of diamonds glow blue when exposed to ultraviolet light and some will even glow green, yellow, white or (extremely rare) red.
While
Diamonds werent
cut until the 14th century and it wasnt until 1725 that deposits were
discovered in
Characteristics
Diamonds are made of pure carbon atoms that exist deep in the ground, exposed to intense heat and pressure over billions of years. Over time, this pressure builds up and forces the diamonds and rocks up toward the surface in a volcanic-like explosion. The explosion creates a very deep, wide hole called a " kimberlite pipe"into which most of the diamonds settle. These pipes resemble gigantic carrots encrusted with diamonds. It can take years to fully excavate an entire pipe.
Diamonds also make it to the surface through wind and water erosion, often in coastal areas scattered around the world.
While diamonds exist in a broad color range, they all posses the following features: high refraction, high dispersion or fire, very low reactivity to chemicals, and extreme hardness.
If diamonds are so hard, how then (you might well ask), are they cut?
The crystalline formation of a
diamond gives it four points of cleavage. A sharp, accurate blow at one of
these points will split the diamond. This is (obviously) a very skilled job and
while it takes years of training the tools of the
trade remain a simple blade and hammer. This is actually a growing industry
with
After cleaving the diamond is shaped. Today this can be done by computerized machinery but more often is still done by hand and typically involves four specialists: The Blocker: who cuts out the rough shape of a diamond; The Top Maker Brilliandeer: who cuts the table and the facets above the girdle; The Bottom Maker Brilliandeer: who cuts the pavilion under the girdle; and the Girdler: who cuts the girdle and the facets around it.
Finally the diamond is polished with fine diamond abrasives creating the stone's many angled planes, or facets. Each facet must be in perfect geometric proportion to every other in order to provide maximum reflection. Only when all these stages have been done is the diamond ready to be set and presented to the buying public.
Diamonds have a high refractive index and dispersion. This is what gives diamonds the brilliance and fire we know. In fact most diamonds are not colorless, but are slightly to noticeably yellow. Intense, attractive colors like yellow, pink, blue, green and rarely red are known as fancy colors.
Evaluation
Diamonds are easier to shop for than other gemstones because they have an accepted grading system that is universal. The most highly valued diamonds are the etremely rare bright red, which have sold for up to $1,000,000 per carat.
A diamonds value depends on the four "C's": clarity, color, cut and carat weight. Color is graded from D (clear) to Z (yellow), while clarity is rated from IF (internally flawless very rare), through VVS (very minute flaws), VS (very small flaws), SI (small flaws), to I (significant flaws).
Diamonds should be faceted so that the maximum amount of light is reflected back through the top of the stone. A poorly cut diamond will appear dull and lifeless. The round brilliant is the brightest cut. While oval, pear and marquise cuts appear larger than rounds they are not as brilliant.
Go back to Gem Table
Emeralds
Colors: Green
Refractive Index: 1.56 - 1.59
Durability: Slightly fragile to tough
S.G.: 2.67 - 2.84
Material: Beryl
Treatment: Assume oiled
Hardness: 7.5 8
Availability: A variety of sizes
Localities:
Price: Low to very expensive
Common Shapes: Emerald cuts, ovals & cushions
Interesting Facts
The mining of emeralds has been dated back to more than 3,000 years ago, during the
time of the Ancient Egyptian Empire. The green fire was so mesmerizing that
the Spanish Conquistadors went on a bloody campaign to find the location of the
emerald mines in
Characteristics
Emeralds contain beryl as the base mineral, while the presence of chromium and vanadium gives this gemstone the green fire. Colombian emeralds are known for their vivid green color, while Brazilian emeralds are known for their variety of color, ranging from light green to fine medium dark green.
It is quite rare to find emeralds of fine quality over one carat in size, for large emeralds sometimes contain eye-visible inclusions, known as jardin or the garden.
With the hardness close to 8 on the Mohs scale, emeralds are quite durable. However, ultrasonic and steam cleaning could damage the stone, causing fractures.
Therefore, professional jewelers
should only clean emeralds.
Evaluation
Clarity and transparency are the most important characteristics when evaluating the value of emeralds. When evaluating from a face up position, very fine quality emeralds should enable the viewer to see the back facet. The brightness of the gemstone, which is determined by the cutting and the number of inclusions, is also an important evaluation factor. Intense medium green emeralds command the highest value. The purity of the green color is crucial to the value and the beauty of the stone, with blue or yellow overtones diminishing its value.
Go back to Gem Table
Garnet
Colors: All but Blue
Refractive Index: 1.72 1.94
Durability: Slightly fragile
S.G.: 3.40 4.30
Material: Various
Treatment: None
Hardness: 6.5 7.5
Availability: Varies with type
Localities:
Price: Low to expensive
Common Shapes: Ovals, round, cushion & fancy shapes
Interesting Facts
The history of garnet goes back as far as the Bronze Age (more than 5,100 years ago), where this gemstone was very popular amongst craftsmen and artisans. According to Christian and Jewish mythologies, when Gods wrath clouded the earth with thunderous storms and endless rain during the Great Flood, a radiant red garnet guided the way for Noah, ultimately leading his ark to salvation.
Malaia Garnet,Mandarin
Unlike other gemstones, garnets are believed to contain both protective and destructive rudiments. The crusaders engraved garnets into their body armors, believing that the protective power of the stones would lead them to safety. On the other hand, some Asian cultures added this gemstone to bullets, believing that garnets destructive power would greatly amplify the enormity of a wound.
The name garnet is believed to have derived from a fruit called pomegranate, which contains reddish color seeds, similar to garnet in color.
Characteristics
Garnets are in actuality a group of related minerals, containing cubic crystalline structure with slight variations in their chemical compositions. In all, there are 7 major
types of garnets, which include Almandine, Pyrope, Spessartine, Grossular, Andradite, Rhodolite and Malaia.
Almandine Also known as almandite, almandine garnets are the most common variety. As a result, many have associated its fine red wine color (violet red to brownish red) as
the garnet color. The size of
almandine garnet varies from small to large. Star almandine garnet can occasionally be found with a rare four-rayed star. Most of the finest almandine garnets today are mined in
Pyrope - Pyrope garnets are another
garnet type which are dark red in color. Most of these
stones available today are mined in
as they are often found in small pebbles close to anthills.
Spessartine -Spessartine garnets, also known as spessartite, are the orange to red orange variety, often referred to as root beer colored garnets. Its name is derived from
Grossular -Unlike other garnet varieties, grossular garnets appear in many colors, extending from colorless, yellow, orange, green to exceptional pink. The most sought after
color of grossular garnets is the medium
dark green variety, known as tsavorite, which is named after
Andradite Andradite garnets are undoubtedly one of the most rare gemstones available today. The intense medium green variety, known as demantoid, is quite spectacular to observe. Having the highest refractive index of all garnets, dematoids brilliance is second to none.
The finest stones will contain some inclusions, called horse tail inclusions, which are fibrous strands of byssolite.
Small amounts of demantoid garnets were mined in
Other color varieties of andradite garnets do exist, however their beauty is incomparable to the stunning brilliance of demantoids.
Rhodolite - Many have considered rhodolite to be the queen of garnets. This is due to its delicate pink to violet red color, which is similar to that of the rhododendron flower (a
common symbol of feminine beauty). Chemically, this garnets composition is a blend of almandine and pyrope.
Rhodolites of most spectacular pink are mined in
Malaia - Malaia garnets, mined only
in
was truly appreciated by the gemstone world. Malaia garnets are available in numerous shades of orange, ranging from soft peach to intense reddish orange.
Similar to rhodolite, malaia garnets chemical composition is a mixture between many general types of garnet, including grossular, spessartine, almandine and pyrope.
Evaluation
When evaluating the value of garnets, color is the most important characteristic. The color must be intense and uniform with a tone that is not too light or too dark. Fine garnets should be eye clean with minimal inclusions under magnification. Size is also a very critical determinant of the stones value. For fine garnets of a rare color, the value of the gemstone will increase tremendously as the size increases.
Colors: White, green, yellow, red, orange, lavender, black & brown
Refractive Index: l.66 - l.68
Durability: Tough
S.G.: 3.30 3.38
Material: Sodium aluminum silicate
Treatment: Dyeing
Hardness: 6.5 7
Availability: Some colors meet demand; others are very rare
Localities:
Price: Low to very expensive
Common Shapes: Cabochons in oval, round, navette, etc. Some carved
Interesting Facts
The "stone of the loins" is how the Spanish refer to jade "piedras de ijada" and this is where the English word derives from. The term jade actually refers to two distinct types of stone that closely resemble one another the more common nephrite and the more expensive jadeite.
Long associated with the Chinese
culture, jade was actually used by the Central
American Mayan civilization hundreds of years before it attained a royal
position in the Middle Kingdom. The Mayans mined jadeite in
The Chinese cult of jade worship
began in the Neolithic era when nephrite from the
Jade is tougher than granite and
more difficult to carve than solid steel. When diamonds were
first introduced to
Although jade has long been associated with the Chinese culture it wasnt until l784 that Burmese jadeite found its way there and superseded the local nephrite as the imperial stone.
The New Zealand Maoris also used nephrite weapons. The fibrous structure of nephrite is very densely packed making it the "super skull crusher" gemstone. In spite of its low hardness, it is considered to be the toughest gem material.
Jade is believed
to bring good luck, health and fortune, assist during childbirth and protect
infants from disease. Throughout
Characteristics
There are two distinct types of jade
jadeite and nephrite. Nephrite is found in scattered
areas around the globe and appears in a wide variety of colors. Jadeite
predominantly comes from
Evaluation
Intensity of color and transparency
are the most important factors in judging quality. While jade is never fully
transparent, the closer it gets to transparency, the higher it is valued. The
most highly valued colors are the very rare Imperial green and apple green.
Lavender jade is also very rare and attains high prices. A green swirl of jade
in an otherwise white stone is known in Chinese as
moss in snow and fetches princely sums.
Jadeite must be examined with a microscope to see if it has any value-reducing internal fractures. Quality of carving is also an important value factor.
Frequently jadeite is dyed green or
lavender. Most dyed jadeite does not look quite right. Jade is
often sold by the piece rather than by carat weight.
Go back to Gem Table
Lapis Lazuli
Colors: Shades of blue
Refractive Index: l.50
Durability: Fairly tough
S.G.: 2.70 - 2.90
Material: Mainly lazurite with traces of hauynite, sodalite, noselite, calcite & particularly pyrite.
Treatment: Dyeing is common
Hardness: 5 - 6
Availability: Supply meets demand
Localities:
Price: Low to moderate
Common Shapes: Cabochons of all shapes, beads & carvings
Interesting Facts
Mined in
with sparkling flecks of pyrite, or fools gold, adding to its mystical allure.
Attributed with great healing, purifying and curative properties, Lapis Lazuli allegedly points the way to enlightenment, and aids in the opening of the Third Eye.
Popular with ancient alchemists (who knew it as sapphirus), it was used in medicine, cosmetics and paintings. It was also believed to confer ability, success, divine
favor, ancient wisdom and cure sore throats. No wonder it was as valuable as gold!
The ancient city of
inscription stone. It was one of the stones in the biblical 'Breastplate of Judgment' of Aaron (Exodus: xxviii, 15-30). But the Romans (typically) believed it to be a
powerful aphrodisiac. In the Middle Ages, it was thought to keep the limbs healthy and free the soul from error, envy and fear.
When lapis was
first introduced to
the pigment which painters used to paint the sea and the sky until the nineteenth century.
Characteristics
Among gemstones, lapis lazuli is the only rock - composed of several minerals rather than a single one. The characteristic blue comes from sodalite minerals, with
any white coming from calcite, and its sparkling gold flecks from pyrite. All lapis lazuli is opaque.
Lapis Lazuli is the second most popular stone for mens jewelry, second only to black onyx, whereas in womens jewelry it most commonly appears as beads or
earrings.
Evaluation
The finest quality is a dark, intense blue with no visible calcite and a mere sprinkling of pyrite. "Royal blue" is a descriptive term for fine material. As the color becomes lighter (indicative of more calcite) the value of lapis lazuli drops, visible calcite is a definite detriment. Quality of cutting is also a value consideration.
The finest quality is from
Go back to Gem Table
Moonstone
Colors: Pastel tints of all colors
Refractive Index: l.5l - l.59
Durability: Not very hard but they are reasonably tough
S.G.: 2.54 - 2.70
Material: Feldspar
Treatment: None known
Hardness: 6 - 6.5
Availability: Supply meets present demand
Localities:
Price: Mostly low, some moderate exceptions
Common Shapes: Cabochons: rounds and ovals
Interesting Facts
Popular with the Romans, who thought
it was formed out of moonlight, and in
A symbol of the Third Eye, moonstone is said to balance yin/yang, protect against epilepsy and sun stroke, cure headaches and nose bleeds, and ensure a high yield in crops. It can help men open their feminine emotional aspects and cool a fever if applied to both temples.
During the full moon, men can use it to predict the future by placing it in their mouths but women should avoid it at this time and also when menstruating.
A favorite of Art Nouveau jewelers, moonstone is a highly prized gift for lovers as it arouses tender passion. It also accentuates the wearers nature, whether positive or negative.
Characteristics
Moonstones characteristic shimmer is known as schiller or adularescence, and is caused by the intergrowth of two different types of feldspar with different refractive indexes. Moonstones are usually cut in a smooth-domed cabochon shape to maximize this
effect.
Moonstones come in a variety of colors, ranging from colorless to gray, brown, yellow, green, or pink. Clarity ranges from transparent to translucent.
Sometimes moonstone will have an eye as well as a sheen. A related variety of labradorite feldspar is known as rainbow moonstone. Its sheen exhibits a variety of rainbow hues.
Evaluation
The best moonstone has a blue sheen,
perfect clarity, and a colorless body color. Fine moonstone is quite rare and
becoming rarer. It is mined in
Blue flash and rainbow moonstones have recently become very popular. Once considered plentiful, they are now rather scarce due to increased demand and prices have risen.
Moonstones are often carved into mini art works with "man in the moon" faces popular. The cost of carvings may fall into the moderate category if they are very unusual.
Colors: Colorless, white, yellow, orange, red, green, blue, brown, gray & black
Refractive Index:l.37 - l.47
Durability:Very fragile
S.G.: l.42 - 2.25
Material: Silicon dioxide, SiO2, & water
Treatment: Occasionally stabilized, dyed, oiled & coated
Hardness: 5.5 - 6.5
Availability: Adequate supply
Localities: Australia, Brazil, Mexico, Honduras, Czechoslovakia, Nevada & recently discovered in central Wyoming
Price: Low to expensive
Common Shapes: Opals with play of color (precious opal) are cut into cabochons of any shape. Fire opals without play of color (common opal) are faceted into various shape
Interesting Facts
With the fire of the carbuncle, the brilliant purple of the amethyst and the sea green color of the emerald, all shining together in incredible union opal clearly impressed Pliny the Elder (23-79 AD), Roman historian and author of the worlds first encyclopedia. The Romans had been wearing opals for centuries and considered them a symbol of hope and purity while for the early Greeks they embodied the powers of foresight and prophecy. The more fancifully minded Arabs thought that opals must have fallen from heaven in flashes of lightning thus achieving their unique play of color or opalescence.
Amazingly this opalescence is a result of the 5-10% of water trapped inside the stone in which rows and rows of tiny spheres of silicon dioxide are arranged, diffracting light in a unique fashion.
Opal has also featured in literature
with Shakespeare referring to it in Twelfth Night as the queen of gems. A
real queen had to intervene in the near destruction of the 19th
entury opal market when Sir Walter Scotts Anne of Geierstein started a
superstition that opals were bad luck for people not born in October. The
novels heroine owned an opal that burned fiery red
when she was angry and turned ashen gray upon her death. Queen
Opal and tourmaline are the official
stones for those born in October, and famous French actress
Sarah Bernhardt rarely left the house unless adorned with her opalescent
birthstone.
Characteristics
The physical structure of opal is
unique. Tiny spheres of silicon dioxide form a pyramid shaped grid interspersed
with water. Tiny natural faults in this grid cause the characteristic
play of color. The effect is similar to the rainbow colors displayed on a soap bubble, only much more dramatic.
Opals vary widely in body color,
with white the most common. Black is considered the
most valuable as it enhances and accentuates the play of color. Fire opal (yellow,
orange or
red) is often faceted and can resemble ruby. Green and blue opals are rare.
Opal is sometimes cut with pieces of matrix - the host rock. This strengthens the opal and can also lend a more interesting appearance. The finest examples are Boulder Opal, which sometimes have an undulating surface of hills and valleys. Their unusual shapes and ironstone inclusions make Boulders popular with progressive, modern designers and wearers.
As opal is relatively soft and
fragile it is often made into doublets or triplets -
backed with plain black opal and fronted with clear quartz. These are ideal for
rings or any piece that is likely to be receiving rough treatment.
Evaluation
Combining body color and play of
color we are faced with infinite possibilities, so
pricing is complex.Size is also a factor with the carat price for larger stones
accelerating accordingly. The intensity of the play of color and the extent to
which it covers the opals surface also count.
Of all the opal taken out of the ground, 95% is valueless potch and 95% of the remainder is low quality. Only a mere 0.25% ever makes it to market.
Go back to Gem Table
Colors: White, cream, gray, black, pink, orange and violet tints, pink & green overtones plus dyed colors
Refractive Index: 1.53 - 1.69
Durability: Fragile
S.G.: 2.68 - 2.85
Material: Nacre
Treatment: Bees wax polish, bleaching, dyeing and irradiation
Hardness: 2.5 - 4.5
Availability: Natural pearls: very rare; cultured pearls: supply meets demand
Localities:
Price: Low to very expensive
Common Shapes: Round, pear, egg, teardrop, baroque, half, three-quarter, blister & more
Interesting Facts
Aphrodites tears of joy, dew drops
filled with moonlight,
The Romans were particularly
enamored of this gem of the sea and
The first known source of pearls was
the
died in 520 BC.
The earliest written record of their
value is in the Shu King, a 23rd-century BC Chinese book in which the scribe
sniffs that a lesser king sent tribute of strings of pearls not quite round.
The Chinese also used pearls in medicinal ways to cure eye ailments, heart
trouble, indigestion, fever and bleeding. To this day pearl powder is still
popular in
Both the Incas and Aztecs believed
that pearls had been imbued with mystical properties
for health, wisdom and prophecy. While the North American Indians were
stringing fres water pearls of the
The Koran states that a good Muslim,
upon entering the
During the Dark Ages, while fair maidens of nobility cherished delicate pearl necklaces, gallant knights often wore pearls onto the battlefield. They believed that the magic possessed by the lustrous gems would protect them from harm.
While Queen Isabella had to hock her
impressive collection of jewelry to fund Christopher Columbus expedition to
discover the new world, the investment paid off as the discovery of pearls in
Central American waters added to the wealth of
Until the early 1900's, natural
pearls were accessible to only the rich and famous. In 1916, famed French
jeweler Jacques Cartier bought his landmark store on
But then in 1919, the son of a Japanese noodle maker perfected and patented a method of cultivating pearls and production of the gems of the sea turned from a treasure hunt into an industry.
Characteristics
A natural pearl (sometimes called an Oriental pearl) forms when an irritant works its way into a particular species of mollusk that is actually closer to a scallop than an oyster. As a defense mechanism, the mollusk secretes a fluid to coat the irritant. Layer upon layer of this coating (known as nacre) is deposited on the irritant until a lustrous pearl is formed.
A cultured pearl undergoes the same
process. The only difference being that the irritant is a surgically implanted
mother-of-pearl bead or nuclei. The best nucleus comes from a
Pearls have long been considered ideal wedding gifts because they symbolize purity and innocence. In the Hindu religion, the presentation of an un-drilled pearl and its piercing has formed part of the marriage ceremony. While in the western hemisphere pearls are the recommended gift for couples celebrating their third and 30th wedding anniversaries.
Evaluation
Almost every pearl on the market these days is cultured. Its only at antique auctions that youre likely to come across naturals. Cultured pearls are still real pearls theyve simply had a helping hand from mankind.
Fakes are usually made from ground fish scales and can be easily detected with the simple tooth test. Gently scrape the pearls along the ridges of your top teeth. If it glides easily, its fake. If you feel a slight gritty abrasiveness, its most likely cultured or natural.
Saltwater pearls are usually more
expensive than freshwater with Akoya Japanese pearls being the most popular.
Freshwater pearls are available in a far wider color range than saltwater, including purple, violet, orange, blue and gray. They are cheaper to produce as each mollusk can yield up to 30 pearls per harvest! American freshwaters are allowed to mature for much longer than all other cultured pearls (up to 5 years, compared to 1 year for most others) resulting in a thicker nacre which gives American pearls an unusually high luster and orient (the iridescence from the light reflected from the inside of the pearl).
White-pink pearls with orient attain the highest prices but with the huge variety of colors available today its best to choose that which compliments your skin tone and hair color.
Be sure to check pearls under several different light sources, against a dark background. Roll the pearls around to make sure that the luster is uniform throughout. Minor blemishes may be buffed or washed away. Pearls are very porous and will soak up just about any substance they come in contact with, especially perfume and cosmetics.
Go back to Gem Table
Peridot
Colors: Yellowish-green to olive-green to brown
Refractive Index: 1.65 - 1.69
Durability: Fragile
S.G.: 3.31 - 3.48
Material: Olivine, which is made up of forsterite (90%) and fayalite
Treatment: Low quality peridot is occasionally treated with oil, wax or resins
Hardness: 6.5 - 7
Availability: Under 5 carats abundant. Larger sizes rare
Localities:
Price: Low to moderate
Common Shapes: All possible shapes in small faceted material
Interesting Facts
Known by the ancient Egyptians as
the gem of the sun, peridot has enjoyed a mystical reputation with its
alleged powers including: warding off anxiety,
enhancement of speech articulation, and success in relationships and marriage.
Common in early Greek and Roman jewelry, peridot has been popular since 1500 BC when the Egyptians started mining it on Zeberget, later known as St. Johns Island, about 50 miles off the Egyptian coast in the Red Sea. It was a dangerous business back then as the island was infested with poisonous serpents, which a later Pharaoh had driven into the sea.
Peridot mining was traditionally done at night when the stones natural glow is easier to see, the ancient Egyptians even believed that peridot became invisible under the suns rays.
Hawaiian natives believe peridot is the goddess Pele's tears, while biblical references to the stone include the high priest's breastplate studded with a stone for each of the twelve tribes of Israel, one being peridot. Cleopatra reportedly had a fine collection of emerald jewelry, which was really peridot but it was the Ottoman Sultans who gathered the largest collection during their 600-year reign from 1300-1918.
Powdered peridot has been used to cure asthma and a peridot placed under the tongue of someone in the grip of a fever will lessen their thirst. Legend has it that drinking from a peridot goblet can increase the potency of medicines.
Pirates believed peridot had the power to drive away evil spirits (and the nights terrors), especially if set in gold. But as protection from evil spirits it must be pierced, strung on donkey hair and worn on the left arm.
Possibly the most unusual peridot is that which comes from meteorites called pallasites. Some have even been facetted and set in jewelry, the only extraterrestrial gemstones known to man.
Characteristics
Peridot ranges in color from light yellow-green to the intense bright green of new grass to olive. Because of the way peridot splits and bends the rays of light passing through it, it has a velvety, "sleepy" appearance - a shining rich glow, and a slightly greasy luster.
Evaluation
The purer green a peridot is, the higher the value. Any tinge of brown greatly diminishes the price as well as visible flaws.
In 1994, an exciting new deposit of
peridot was discovered in
Go back to Gem Table
Rubies
Colors: Reds
Refractive Index: 1.76 - 1.78
Durability: Tough
S.G.: 3.9 4.1
Material: Corundum
Treatment: Assume heating
Hardness: 9
Availability: Fine rubies up to five carats
Localities:
Price: Low to very expensive
Common Shapes: Ovals, cushions, pear, emerald cuts & others
Interesting Facts
The earliest record for the mining
of rubies goes back to more than 2,500 years ago in
Today,
Characteristics
Rubies and sapphires are closely related, having corundum as their base mineral.
The difference in color occurs because of the different trace minerals
contained within each gemstone. Thai rubies tend to have a darker color and
less intensity than Burmese rubies, which are known
for their high quality and high price range; however, very fine rubies can be
found in
Rubies come in many different shapes and sizes, providing great variety to gemstone lovers. With hardness just below that of diamonds, rubies are one of the toughest gemstones, and with no cleavage, breakage rarely occurs.
Microscopic inclusions, sometimes called silk, are normal characteristic of rubies. However, heating tends to dissolve these inclusions. The existence of inclusions provides traces to the rubies origin and can be used to separate natural from synthetic stones. The inclusions within these gemstones may also be evidence that a ruby has not been heat-treated. Inclusions do not effect the value of the stone as long as the brilliance of the gemstone is maintained and are not visible to the naked eye.
Evaluation
Intensity and uniformity of the red color are the factors used to determine the price of rubies. Highly valued rubies are those with intense medium red and uniformed color. Intense pink rubies can be highly appraised as well, if they are clear and beautifully cut.
The evaluation of rubies should be done under different light settings. When viewed under very strong light, rubies may show very intense color; however, when viewed under normal lighting, the gemstone may appear less intense. Light is therefore a very important factor in determining the true color of rubies.
To help assess their symmetry, rubies must be judged from their face up position and their overall beauty should always be taken into consideration.
Go back to Gem Table
Sapphires
All Colors
Refractive Index: 1.76 - 1.78
Durability: Tough
S.G.: 3.9 - 4.1
Material: Corundum
Treatment: Assume heating
Hardness: 9
Availability: Fine sapphires up to
ten carats Localities:
Price: Low to very expensive
Common Shapes: Ovals, cushions, pear, emerald cuts & others
Interesting Facts
The
Sapphires come in all spectrums of
color, except for red. Often when people refer to sapphires, they mean blue
sapphires. Other color sapphires are referred to as
fancy sapphires.
Characteristics
Common Characteristics -Similar to
rubies, sapphires come in many different shapes and sizes, providing great
variety to gemstone lovers. With hardness just below that of diamonds,
sapphires are one of the toughest gemstones, and with no cleavage, breakage
rarely occurs.
Blue Sapphires
Intense medium dark blue is the most
sought after color for blue sapphires. However, very fine sapphires are
extremely rare.
Fancy Sapphires
Found in
Star Sapphire.
Star sapphires are very interesting, having a six-rayed star in the middle of the stone. This asterism occurs when the titanium inclusions within the stone form into the shape of a star. Star sapphires come in all shapes and sizes, but black star sapphires are the most common.
Evaluation
Blue Sapphires
Intensity, uniformity and purity of color are the most important considerations when making a decision about the purchase of a blue sapphire. Fine blue sapphires should not contain any overtones or secondary colors, for this will lessen the beauty of this precious gemstone. As the overall beauty of the stone will depend on the cutting, this characteristic must always be taken into consideration. Dark blue sapphires will appear black under low light settings, while fine blue sapphires will maintain their color in any light setting.
Fancy Sapphires
For fancy sapphires, the wearers preference is the most important determinant, since these gemstones come in many different shapes, colors and sizes. Again, intensity, uniformity and purity of color are the most important factors. Once again, cutting of fancy sapphires will also be another important evaluation factor.
Star Sapphires
The concentration of color is the most important factor for judging the beauty of these stones. The shape of the star must be sharp and in the center of the stone in order to accentuate the beauty of this unique type of sapphires. A star sapphires translucency can never be neglected, for greater translucency relates to a higher value. The star of natural star sapphire can be viewed when a specific light source is pinpointed onto the stone.
Go back to Gem Table
Spinel
Colors: Red, pink, orange, blue, violet, golden yellow & gray
Refractive Index: 1.71 - 1.72
Durability: Tough
S.G.: 3.57 - 3.9
Material: Spinel
Treatment: None
Hardness: 8
Availability: Pastels common, intense colors maybe hard to find, most stones under 5 carats
Localities:
Price: Moderate to expensive
Common Shapes: Mostly ovals, cushions & rounds
Interesting Facts
Throughout history, the red
brilliance of spinel has led to great confusion, causing many to mistakenly identify this astonishing gemstone for ruby.
In fact, the worlds most famous rubies are actually spinels. For example,
the 170-carat Black Princes Ruby on the British Imperial State Crown and the
352-carat Timur Ruby have been authenticated as
spinels by leading gemologists. The source of confusion stemmed not only from
color similarities, but is also attributed to the
close proximity of their deposits.
Exceptional stones are found on the
Characteristics
Spinels come in many different color
varieties, with hot colors, such as red, orange and vibrant pink, being the
most expensive. Exceptional blue stones, also known as cobalt spinels, which
resemble fine sapphires, have been discovered in
Having the hardness of 8 on the Mohs scale, with no cleavage spinels are excellent for jewelry settings.
Evaluation
When evaluating the value of spinels, color intensity is the most important consideration. The gemstone should be intensely colored without any secondary brown tones. Clarity is also an important evaluating factor, with eye clean spinels being highly valued.
Cutting is very important, as well cut stones can be quite spectacular. Having a high refractive index, the brilliance of a well-cut spinel is breath takin
Go back to Gem Table
Tanzanite
Colors: Blue to violet
Refractive Index: 1.69 - 1.70
Durability: Fragile
S.G.: 3.20 3.40
Material: Zoisite
Treatment: Assume heating
Hardness: 6 7
Availability: Supply meets demand
Localities:
Price: Moderate to expensive
Common Shapes: Oval, cushion & fancy shapes available
Interesting Facts
The showcase of this newly
discovered gemstone by Tiffany & Co. in 1967 captured the worlds
attention. It is believed that the Masai herders were
the first people to discover this gemstone. According to popular myth, a
lightning strike near the Merelani hills set surrounding grasslands on fire.
When the Masai herders return to the area with their livestock, magical blue
stones appeared on the ground. When a Portuguese geologist, named DeSouza,
traveled to this area in
With vast deposits in the northern
part of the country near the Merelani hills,
Characteristics
When heated to 600 degrees Celsius, greenish to brownish zoisite undertakes an incredible metamorphosis, resulting in the creation of this vibrant blue to blue violet gemstone, tanzanite. With hardness between 6 and 7 on the Mohs scale, tanzanite is quite fragile, and for this reason, ultrasonic should never be used to clean this precious stone.
In its early discovery, tanzanite was only available in small stones; however, today, larger stones have been made available, providing greater variety to the gemstone market.
Evaluation
The lighting condition is the most critical factor when evaluating the value of this gemstone. Tanzanite will display the most blue under daylight, while the violet shade will be more apparent under incandescent light. The stone which commands the highest value is generally the one which displays minimal violet, even when it is viewed under incandescent light.
It is common to find flawless tanzanite crystals; therefore, the stone should not contain too many inclusions.
Go back to Gem Table
Topaz
Colors:
Yellow, orange, pink, blue, brown, red & colorless
Refractive Index: 1.60 1.64
Durability: Fragile, has cleavage
S.G.: 3.50 3.57
Material: Silicate
Treatment: Irradiation and heating of some colors
Hardness: 8
Availability: Some color are abundant, red is very rare
Localities:
Price: Low to expensive
Common Shapes: Blue in all shapes; other colors in ovals, cushions & emerald cuts
Interesting Facts
The utilization of topaz goes back to the days of the Ancient Egyptian Empire. Its popularity grew tremendously during the Middle Ages, where people believe topaz to have the power to strengthen the mind. Many astonishing pieces of jewelry were created with this sparkling gemstone. In the past, many refer to topaz as a yellow to orange gemstone, but due to the large supply of blue topaz in the world market today, many are led to believe that topaz is exclusively a blue gemstone. The modern word topaz is derived from the Sanskrit word tapas.
The worlds largest supplier of
topaz is
Characteristics
Topaz comes in a variety of shapes, colors and sizes. Its brilliance and clarity will be able to attract the attention of those who see this gem. With the hardness of 8 on the Mohs scale, topaz is very difficult to scratch; however, the gems maybe brittle.
Evaluation
Red and intense pink are the most rare and most desirable colors for topaz. A gem with these colors will command a relatively high price. Bright orange color topaz, also known as the imperial topaz, falls into the moderate price range and are easier to find. Blue Topaz, having a low to moderate price range, is very popular, because a variety of shades, sizes and shapes are available.
The true determinant for the evaluation of this precious stone will be the wearers preference. The intensity of color and the clarity of the stone will contribute to the value of topaz as well, and should never be neglected.
Go back to Gem Table
Tourmaline
Colors: All colors
Refractive Index: 1.62 -1.64
Durability: Fairly Tough
S.G.: 3.01 - 3.21
Material: Aluminum & boron silicate
Treatment: Heating for some colors
Hardness: 7 - 7.5
Availability: Supply meets demand
Localities:
Price: Low to expensive
Common Shapes: Emerald cuts, cushions, ovals & some fancy shapes
Interesting Facts
As it is found in all spectrums of color, Tourmalines are often described as the chameleon gemstone. It is not surprising to find a fine tourmaline that mirrors the exact semblance of other gemstones, such as emerald, ruby and sapphire. Some tourmaline crystals may even appear as crystallized rainbows with several bands of color, ranging from the most brilliant red to the deepest blue. Many refer to tourmaline as the muses stone, for they believed that its imaginative colors contain inspirational powers which enable the mind of its beholder to bring forth illimitable vision and creativity.
During the Manchu Dynasty in
The name tourmaline is believed to have derived from the Sinhalese word, turmali, meaning mixed.
Characteristics
Tourmaline comes in all spectrums of
color, the most common being green and pink. The red variety is
often referred to as rubellite, as its vibrant red color often
resembles that of the finest rubies. A rare green chrome variety of tourmaline
found in
Tourmaline is available in all sizes ranging from small to over 100 carats; however, stones of a rare color are often found in smaller sizes. For example is extremely uncommon to find fine rubellites over 20 carats in weight.
Some color varieties of tourmaline are more included than others. For example it is common to find bi-color and multi-colors stones with visible inclusions.
Evaluation
Similar to the evaluation of other
precious stones, the intensity of color and the clarity of the gemstone are the
most important considerations. Green chrome and
Go back to Gem Table
Zircon
Colors: Blue, green, yellow, orange, brown, red & colorless
Refractive Index: 1.78 - 1.94
Durability: Fragile
S.G.: 3.95 - 4.8
Material: Zirconium Silicate
Treatment: Heating for some colors
Hardness: 6.5 7.5
Availability: Small blue stones can be found; others are rare
Localities:
Price: Low to moderate
Common Shapes: Mostly rounds & ovals for best brilliance
Interesting Facts
For many centuries, the brilliance of zircon has captured the hearts of those who set their eyes on this magnificent gemstone. Zircons popularity began to grow in the sixth century, when Italian artisans featured the stone in jewelry designs. During the Ages, zircon was believed to contain remedial power, protecting the
wearer from diseases and banishing insomnia. The name zircon is believed to have derived from the Arabic words, zar, meaning gold, and gun, meaning color.
provide a large supply of this marvelous gemstone to the world market.
Characteristics
There are three natural types of zircons: low, medium and high. The variance is due mainly to the differences in the specific gravity and refractive index.
Having the highest refractive index among any natural gemstones, with the exception of diamonds, the brilliance of high zircon is second to none. As temperature rises the refractive index of zircon also increases, making the gemstone even more spectacular. Despite its brilliance, Zircon is quite brittle and can easily be chipped or scratched.
A very unique
characteristic of zircon is that they are birefringence, meaning that light
splits into two rays as it passes through the stone. As a result, the back
facets appear as double images.
Zircons are often blue or colorless. Other color varieties, such as yellow, orange, green, brown and red, do exist, but they are extremely rare.
Evaluation
The intensity of color and the clarity of the stone are the most important criteria when evaluating zircon. The presence of visible flaws greatly diminishes the value of this stone. Deep blue and natural red zircons are the most sought after varieties. Intense blue, orange and red zircons over 3 carats in size fall into the moderate price range.
Smaller stones with ordinary colors will fall into the lower price range.