Diamond Designs and More

Colored Gems

 
Ruby, Sapphire and Emerald



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Ruby & Sapphire

The Ruby and the Sapphire belong to the Corundum family of gemstones. In terms of hardness, corundums are the next most hardest gemstones after diamonds. Rubies are simply red sapphires. The term sapphire is most commonly associated to the blue sapphire, but the color spectrum of sapphires is quite large. Like diamonds, rubies and sapphires are quite rare and very precious. In fact, large three-carat rubies and sapphires can fetch three times the price as a similar sized diamond. In general, though, diamonds are the more valuable stone.

The most interesting and comprehensive web site about rubies and sapphires can be found under the following links (we will not assume any responsibility or liability for the contents of these suggested links):

 Recommended Reading on Rubies & Sapphires

however, as the information, therein is quite detailed and lengthy, a summary of the most important features about these gemstones are summarized in the following sections.

As in diamonds, rubies and sapphires are also valued by their 4 C’s (Color, Clarity, Cut and Carat Weight), however unlike diamonds, Color is the most important feature for buyers of this gemstone.

4 C’s of Rubies & Sapphires

General Information

Internal link up to chapter Color


Hue, tone and intensity are the three important scales in measuring these gemstone’s colour.

  • Hue refers to the shade of colour within a colour spectrum.
  • Tone refers to the lightness or darkness of the colour, and the uniformity of its distribution throughout the stone.
  • Intensity refers to colour purity or strength of the colour. The Gemological Institute of America has prepared a useful scale to judge a corundum colour’s purity from best to worst: i) vivid, ii) moderately strong, iii) very slightly brownish or grayish, iv) slightly brownish or grayish, v) brownish or grayish

Ruby
The hue of a ruby is red. The tone of its colour ranges from dark to light, which is to say from dark burgundy red (like semi precious garnet gems), to a deep glowing red, and even pink and light pink. The more intense and well distributed each of these colour tones are the better the quality of ruby, irrespective of its colour tone.

Blue Sapphire
The hue of a blue sapphire is blue. Shades of gray and black in blue sapphires are not desirable. As in the ruby, the tone of the colour ranges from dark to light, but the mid to darker tones are preferable. The more intense and well distributed each of these colour tones are, the more glowing the appearance of the blue sapphire and hence the better its quality.

Fancy Sapphires
Any sapphire that is not a blue sapphire is called a fancy sapphire. The hues of these sapphires can be pinkish-orange, pink, orange, purple, yellow and green in order of value.

  • Padparadscha Sapphire - is a beautiful pinkish-orange. These stones are extremely rare and very expensive. Ensure that both the pink and orange can be seen simultaneously as only if this qualification is met can the sapphire be called a Padparadscha sapphire. The preferred tone is light to medium, and the intensity should be vivid.
  • Pink Sapphire - can be mistaken for a pink sapphire. True pink sapphires will have a purplish hue which make them easy to differentiate from their red cousins. The preferable tone is light to medium with vivid intensity. Lower quality tones are too brown or too much purple
  • Orange Sapphire - can be mistaken with the much more valuable pinking orange Padparadscha sapphire. The hue should be red-orange with a medium-dark tone. Orange sapphires with a yellowish tint are less valuable.
  • Purple Sapphire - have plum red hues with medium-dark reddish tones. Avoid gray or brown hues. An interesting feature of purple sapphires is that they change colors. Outdoors they appear blue while indoors they appear violet. The intensitity of the colour should be strong and vivid.
  • Yellow Sapphire - are ideally vivid, light-yellow gemstones with high transparency and, at times, some hints of orange. Unlike the other sapphires, higher clarity is important.
  • Green Sapphires – are not recommended as jewelry gemstones. They usually range from yellow to blue-green and preferably will have medium to dark tones. For vivid green coloured gems, emerald is the best choice.

A final word on colour:

Nearly all sapphires and rubies are heat treated to enhance their colour. Colour enhancements do not result in synthetic gemstones, but corundum gemstones which do not have colour enhancements are usually more valuable if they are equally strong and vivid in colour. Colour enhancements are desired by buyers, as they give the stone a deeper more glowing colour. Heat treated stones can be identified in that the fine silk inclusions are shriveled to a little white dot. Don’t mistaken heat treated stones for internally flawless synthetic stones.

Colour is an individual taste. The colour value of a stone may be quite high but still not match your skin tone. Like with lip sticks, it is generally recommended to test the colour of the stone next to your skin to verify whether the colour suits you.

Internal link up to chapter Clarity

Unlike diamonds, fine blemishes and inclusions are a quality feature of the corundum family of gemstones. This makes it difficult to judge clarity. As a general rule, corundum gems should be eye-clean, that is there are no inclusions visible to the unaided eye, however given magnification, extremely fine silk throughout the stone can actually enhance the beauty of the corundum gemstone. So in essence, the stone should be transparent, yet slightly hazy.

Clarity is a measure of how free from claws a gemstone is. Internal flaws are called inclusions and may block colour consistency. They appear in the form of cracks, crystals, silk, cavitites, chips and other color hues. External flaws are called blemishes, and they may appear in the form of scratches, pits, nicks and abrasions.

As in diamonds, clarity is measured against a scale of degree of inclusions ranging from VVS (very very slightly included) to I (included) and worse. The clarity grade IF (internally flawless) does not exist for corundums. Flawless rubies and sapphires are fake or synthetic stones.

Ruby
There is no such thing as a flawless ruby. Every genuine ruby has a variety of flaws present, and clarity is the term used to determine how free from flaws a ruby is. Rubies however do in general contain more flaws than sapphires. Flaws should not render a ruby vulnerable to breakage or adversely affect its color consistency.

Sapphire
There is no such thing as a flawless sapphire. Every genuine sapphire has a variety of flaws present, and clarity is the term used to determine how free from flaws a sapphire is. Sapphires however do generally contain less flaws than rubies. Flaws should not render a sapphire vulnerable to breakage or adversely affect its color consistency or transparency. The lighter the colour the more more free from flaws the sapphire should be (e.g. yellow sapphires).


Internal link up to chapter Cut

Unlike diamonds, the cut of rubies and sapphires is not nearly as significant as their color and clarity features. Corundums are cut to maintain maximum weight while exhibiting optimal color and brilliance. Cut refers to a) shape (round, oval, pear, rectangle, etc), b) proportion (symmetry and depth proportion between crown top and pavillion bottom), c) style of facet, and d) finish. As corundums are not internally flawless, light reflection plays a smaller role than in diamonds. While the shape of a gem and the style of its facet is subject to individual taste or requirement in a design, its overall symmetry should be consistent, i.e. an off-centre culet (bottom point) immediately results in a bad quality cut..
The finish of gemstones refers to its polish. Tiny blemishes, scratches or surface graining can all lower a corundums polish grade.

Internal link up to chapter Carat Weight

Corundum is a very dense gemstone. A one carat corundum may therefore be smaller than a one carat diamond or other precious gemstones. Given good colour and clarity, the larger the carat number, the more valuable the gemstone. Larger sized corundums appear more beautiful than chip sized gemstones, that is corundum stones smaller than 0.03 carats, therefore avoid using chip sized rubies or sapphires in your jewelry.

Internal link up to chapter Quality ranking of rubies by country

The www.ruby-sapphire.com link further gives an account of Quality Ranking of Rubies by Country:

An approximate ranking of important ruby origins is given below. This applies only for the finest untreated qualities from each source and is but a general approximation. In other words, a top-quality Thai/Cambodian ruby can be worth far more than a poor Mogok stone.

1. Mogok, Burma
2. Sri Lanka
3. Madagascar
4. Möng Hsü, Burma
5. Thailand/Cambodia, Vietnam, Kenya/Tanzania

Mogok
The most well known type of ruby is the Mogok ruby from Myanmar (Burma). While Mogok is the traditional source of the world’s finest rubies, good stones are rare. Pigeon’s blood was the term used to describe the finest Mogok stones given their red fluorescence color. The best stones contain tiny amounts of light-scattering rutile silk. It is this combination of features that gives these rubies their incomparable crimson glow. In Mogok rubies, the color often occurs in rich patches and swirls, and color zoning can occasionally be a problem. The shape of Mogok ruby rough generally yields well-proportioned stones.

Sri Lanka (Ceylon)
Some of the world’s finest rubies have come from Sri Lanka’s gem gravels. Top grade Sri Lankan reds are virtually indistinguishable from their Mogok brethren, but most tend towards purple or pink. As with Sri Lanka sapphires, color accumulates in large stones and so they can be quite magnificent in sizes of five carats or more. Due to the bipyramidal shape of the rough, many stones are cut with overly deep pavilions. Sri Lankan ruby is strongly fluorescent and stars are common.


Generally Heat Treated Gemstones

Madagascar
Known in olden times as the “Beryl Island,” Madagascar was long considered mineralogical nirvana. And today, it is equally known for its gem wealth. Traditionally, Madagascar produced mainly fine blue sapphires and pinks but recently two important ruby deposits have been discovered. Vatomandry source is said to produce the better-quality stone, being lighter and brighter (more reminiscent of Burma), while the Andilamena sourced stone is somewhat darker and not as clean. Rutile silk seen in some pieces suggests that star stones may be forthcoming. Much of the material from both deposits is heat-treated.


Möng Hsu (Myanmar)
When the Möng Hsu deposit came on stream in 1992–93, it took the ruby world by the storm. Suddenly, we were awash in a sea of red the likes of which had never been seen before. And fine stone it was, too. This was not the garnet-like hue of Thailand, but a rich, fluorescent red.
In 1992, the Möng Hsu (Maing Hsu) deposit in Burma’s Shan State began producing good material. This has continued to the present, so much so that close to 90% of the fine cab and facet-grade ruby in the world market is from this deposit. But most cut stones are under two carats.
Möng Hsu material can be extremely fine, but virtually all is heat treated, and most is also flux-healed.


Thailand/Cambodia Rubies
This material’s main attribute is its high clarity, but the flat crystal shapes generally yield overly shallow stones. Due to the high iron content, which quenches fluorescence, most stones tend to have a garnet-red color. An additional problem is the total lack of light-scattering silk inclusions (star stones are not found). Although heat treatment does make improvements, it is not enough. In Thai/Cambodian rubies, only those facets where light is totally internally reflected will be a rich red; the others appear blackish, as with red garnets. Thai stones are actually less purple than most Burmese rubies. However, Burma-type rubies appear red all over the stone. Not only is a rich red seen in the areas where total internal reflection occurs, but due to the red fluorescence and light-scattering silk, other facets are also red.
With the decline in Burma production during the 1962–1990 period, the market became conditioned to Thai/Cambodian rubies, with some people actually tending to prefer them (in the land of the blind, the one-eyed man is king). Thai/Cambodian rubies are acceptable only when good material from the Burma-type sources is not available. Today, production from the Thai side of the border is zero, and that from Cambodia is negligible. One occasionally hears statements about how Cambodian stones are superior to those from across the border in Thailand. This is untrue. The deposits are essentially one, directly straddling the border.


 

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Emerald

The Birthstone for the month of May.

Emerald is commonly known as the "Queen of Gems", and has been treasured for at least 5,000 years. Traveler's relied on emeralds as protection against the hazards and perils of long journeys. Emerald also symbolizes rebirth, fertility and youth.

Emeralds are mined in Columbia, Brazil, Zimbabwe and Zambia.

When purchasing an emerald, the 4 C's of value (Color, Clarity, Cut and Carat Weight) all play an important role, however, Color will generally be the most important factor.

4 C’s of Emeralds

General Information

Internal link up to chapter Color

Emeralds can range in color from bluish-green, to green, to yellowish-green (not as common). The hue is not the only aspect that affects the overall color of this gemstone though. The tone (lightness to darkness) and the saturation (vividness of the hue) also affect the color. If the tone is too dark, it may mask the luscious green hue. If the saturation is too dull, the emerald will look washed out and grayish. The most valuable emeralds have a green or bluish-green hue, a medium tone, and a strong saturation.

Internal link up to chapter Clarity

 

Clarity is the rarity factor that indicates the degree to which an emerald is free of internal inclusions and external blemishes, called "clarity characteristics". Generally speaking, the more inclusions there are, the less transparent a gemstone will be, and the less expensive it will be.

Most all emeralds have natural inclusions of some kind, which is why they are clarity graded with some leniency. It is extremely rare to see an emerald completely free from inclusions. The inclusions in emerald are often referred to as "Jardin" meaning garden of inclusions. Too many inclusions, though will make the emerald look milky and it will no longer be transparent.

Because of the nature of emerald's inclusions (fractures and liquid), they should not be subjected to high temperatures, such as a jeweler's torch, ultrasonic cleaner, steam cleaner, or even hot dishwater. This may cause the liquid to shift in the emerald, and cause the emerald to fracture further.

Internal link up to chapter Cut

"Cut" generally refers to the shape of the emerald. Emeralds can be cut into most all shapes, however, the most common shape for emerald is the step cut and is most commonly referred to a the "emerald" cut. Cut can also refer to the dimensions and proportions of the emerald. The proportions are what make an emerald appealing, look balanced from left to right and top to bottom, and give it optical efficiency. Colored gemstones are not cut to such rigid dimensions and angles as are diamonds.

When cutting a colored gemstone, the cutter thinks about saving the most weight from the rough (gemstone before it is cut), and about bringing out the best color possible. The cutter can affect the color of a gemstone just by the way he/she cuts it from the rough. If the rough is too light, the cutter may cut the emerald with a deeper pavilion (bottom of gemstone) to make it look darker. If the rough is too dark, the cutter may cut the emerald more shallow to allow more light to pass through it, thus making it lighter in color.

Internal link up to chapter Carat weight

If all other factors are equal, the larger the emerald, the more valuable it is. Emeralds are quite dense, and for this reason, a one carat emerald may look smaller than other gemstones. Compared to rubies, though emeralds will look larger.

Our colored stone buyers work with loose emerald dealers from around the globe to offer the most beautiful selection of emeralds, with luscious greens that make the term "emerald green" famous. We feature emeralds from Columbia, Brazil, Zambia, and Zimbabwe.

Internal link up to chapter Treatments

Early emerald miners sought to enhance the color and clarity of emeralds by immersing them in clear oils and waxes. It was found that clear oils and waxes made surface reaching fractures almost invisible to the unaided eye. This technique is still used today, but with more advanced technology. Resins are now often used to fill the surface reaching fractures in emeralds, then, the entire emerald is covered with a hardener, to make the filler more stable. Sometimes the oil may be colored green, to enhance the color of the emerald. The colored oil is not as widely accepted as clear filler, though. Fracture-filling, which is essentially performed on all emeralds in the trade, is not permanent. If the treated emerald is subjected to high heat from a jeweler's torch, an ultrasonic cleaner, a steam cleaner, or even hot dishwater, the filler may seep out of the emerald. If this should happen, however, it can be replaced.



 

 
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