Diamond Jewelry King » inclusions

Rubis

King of diam — Sat, 19 Sep 2009 23:05:44 +0000

Ruby is a specie of corundum and ranges in color from orange-red to purple-red. It is medium light to very dark in tone and quite strong in saturation.
Chemical composition of a ruby is Al203 It is a hexagonal crystal that often comes in six-sided prisms, terminated by flat faces.
Ruby registers a 9 on the hardness scale and is quite tough, unlike the emerald, and not nearly as subject to breakage. Under long wave ultraviolet, a ruby will fluoresce red or orange-red to inert and under short wave should fluoresce moderate red to orange-red.
Rubies come from a number of areas including Burma, which is usually considered as the finest source of rubies in the world. The best Burma stones are medium dark and vivid red.
Thailand produces stones which are a bit dark in tone and range from purple to brownish red because they have a slight bit of iron in them. Africa (Kenya, Tanzania) produces stones that are normally highly included although reminiscent of Burma in color. Sri Lanka has occasional rubies but more often sapphires that often mask as rubies.
In the U.S.A., North Carolina and Montana produce a few stones. Australia produces fairly poor quality stones as does India and Colombia, Nepal and Pakistan.
Rubies tend to be valued partially by the country of their origin. Some rubies now come with authenticated certificates of origin and the word Burma will bring a characteristically premium price even when considered next to a Thai
ruby that may appear identical to the Burma ruby under incandescent light.
Under fluorescent light, the Burma ruby will appear to fluoresce slightly and take on a deeper saturation. This is a highly sought after quality. Burma rubies also have some fine rutile needles that are commonly referred to as “silk” that add rather than detract to the attractiveness of the stone and further establish it as a Burma stone.
In order to establish a country of origin, a certified lab such as the American Gemological Laboratories in New York, has to study the ruby for body color under various conditions, fluorescence and inclusions. If a ruby is certified
as a top Burma ruby, the price may be 1 1/2 or twice what it was as an unknown or as a presumed Thai ruby.
Rubies from Thailand tend to have a brownish or purplish overtone. Those from Sri Lanka are generally very pink in color and more correctly referred to as pink sapphire.
There are a number of ways to treat rubies to improve their color, clarity and ultimately, their value. The quick fix method is to dye or oil the ruby which will help hide fractures, inclusions and improve the color of the stone.
A further refinement of this is a diffusion process where stones are immersed in a chemical bath which contains a number of chemicals including chromium which gives the ruby its color in the first place. This color is carried in
the skin of the ruby by the chemicals and actually penetrates the skin. This generally produces a light tone and the tone is only a skin which will disappear upon repolishing.
The next common treatment is a heat treatment. Rubies stand heat far better
than emeralds do and it is fairly Gommon to heat both rubies and sapphires which tends to improve the color by driving out bluish or brownish tints and will tend to dissolve the transparency, lessening the “silk” inclusions on heavily included stones.
These treatments all are dependent upon temperature, time and cooling rate, but they will bring about a permanent change in the stone leaving no chemicals or treatment to be removed.
In top ratings, rubies are rarer than diamonds but the actual supply of top stones may vary greatly because of political situations. Many stones reach the world markets because they have been smuggled out of places (especially
Burma) through Thailand and other friendlier countries. There is a fair amount of profit to be made in the smuggling of rubies.
Smaller, included or industrial strength stones, are cheaper than their diamond cousins because they are more easily available.
The rhodolite garnet often approaches ruby in color, although tends to be more purplish than the ruby and less saturated but still are sometimes sold as rubies.
Tourmaline also occurs in many color ranges including ruby red and is sometimes sold as ruby.
A new stone called red spinel has a remarkable resemblance to ruby and is not often seen on the market because it is generally sold as a ruby.
Rubies have been synthesized since the late 1 800′s. There are two primary methods of synthesizing rubies – the fusion method and the pulling method. In the 1950′s, several manufacturers began flux growing rubies which takes considerably longer than the other methods and produces a stone much closer to its natural version. Flux grown rubies tend to be extremely clear and transparent with an orange overtone.
Fusion stones tend to be strikingly flawless looking while the flux methods may actually produce a number of inclusions resembling silk.
One clue to synthetic rubies is the cut. Because the material is cheaper and waste is not as much a problem, machine cuts such as square or rectangular cuts are more prevalent.

Emeralds

King of diam — Sat, 19 Sep 2009 22:56:54 +0000

Emeralds are a green crystal of beryllium-aluminum silicate. The chemical formula is Be3Al2(SiO3). They are hexagonal prismatic crystal with a hardness of 7 1/2 to 8 on the Mohs scale. They are not tough stones and may be broken easily by mishandling or the use of severe chemicals or ultrasonic cleaners. If you own an emerald, be careful of it. Don’t wear it during sports. Don’t have a jeweler clean it in an ultrasonic cleaner as it may shatter.

Emeralds also break under applications of heat and should never be in a ring that is soldered. Under ultraviolet light they may fluoresceslightly, orangish red to red, or they may be inert.

Emeralds come from a number of sources. The best come from Colombia. These are the purest colored and generally the finest stones. The emeralds from Brazil are lighter, have more inclusions and are generally smaller than from other areas. Zambia, Africa, produces some bluish stones and some near-Colombian stones. Zimbabwe is home to a particular emerald known as the sandawana emerald which is generally small with a rich green color. Anything over 1/3 carat is rare.

South Africa produces some low-quality emeralds. Tanzania produces a few very good quality emeralds. Pakistan has just discovered some high-quality emeralds. Afghanistan tends to produce flawed but good colored emeralds. USSR does produce emeralds but doesn’t like to let them out of the country. Australia produces some dubious quality emeralds and North Carolina a few gems. Austria and India occasionally produce emeralds.

Emeralds are not unusual as the word emerald simply indicates an extremely nice version of a fairly common stone known as beryl. It is possible to buy something legitimately called an emerald for about $5 a carat. Obviously this is full of flaws, not transparent and so impure in color it looks more like jade than an emerald. They would never be sold in a jewelry store but emeralds do sell on TV and some of the better magazines for $5 per carat.

Gem quality emeralds range anywhere from $400 to $18,000 a carat, depending upon their quality. As the stones get larger, they become increasingly rare and sell for considerably more money.

Color is a critical factor in emeralds and constitutes about half of the stone’s value (clarity 30% and cut 20%).

Hue describes the primary color and any other colors in the stone. Most emeralds are green hued with a bluish hue also visible, especially the better Colombian-type emeralds.

Tone is the depth or darkness of the color as perceived by the eye.

Saturation is the amount of hue present in any given color.

Depending upon where the emeralds come from, they can exhibit a wide range of color; i.e., Brazilian emeralds are usually lighter toned and less saturated than their Colombian cousins.

The green in the emerald is caused by trace elements of chromium and/or bandium. If the color is very light green, the stone is more correctly referred to as green beryl, not emerald.

Emeralds are often oiled to help their appearance. Normally an uncolored oil such as Merck cedarwood oil is used. The stone may soak in the oil for several days and will actually take the oil in somewhat, helping bring out the color and “wedding” on some of the dry inclusions, making the stone look better.

If one finds an emerald that is mild in color or has a grayish hue, it is a good bet to soak it in oil a couple days and it may regain its green color, not to mention its value.

A more unscrupulous “improvement” is to use dye or oil with color in it. It is possible to influence the color of a stone by having it soak up colored oil.

Other problems with buying emeralds are the fact that there are a number of stones that look like emeralds and overlap colors. Tsavorite, a garnet found in Kenya and Tanzania, looks quite a bit like emerald and has a pure green hue, although it tends to be a little bit more yellowish and never has the blue hue of emerald.

Chrome tourmaline is another stone that looks much like an emerald with a moderately strong green color. Another emerald look-alike comes from Africa and is called chrome diopside. All these stones can, and are, sold as emeralds to the unwary.

Different emeralds from different areas tend to have individually shaped inclusions; i.e., slight pyrite inclusions are typical of emeralds from Colombia although they can be seen in stones from other sources.

A three phase inclusion that shows up under a 1 Ox or stronger microscope, which has a distinctly liquid area, a gas bubble in a solid square rock crystal, salt Iying superimposed on each other inside a jagged edged cavity, is typical of emeralds from Colombia and proves their natural origin.

Tropiche emeralds from Colombia sometime exhibit six fine radiating arms of black carbon inclusions, spoke-like in appearance. Another type of this stone has six arms of emeralds extending from the center of the crystal with a white shaped wedge area in between. When these stones are cut and mounted, they are valuable because of their inclusions.

Emeralds are subject to not only customs duty but market restraints as there is no OSO type organization supporting them. It is possible, if one is smart and has verification equipment, to buy emeralds in other countries, notably South America, and smuggle them to America for profit. Coincidentally, the areas one smuggles emeralds from are the same areas one smuggles cocaine from and these passport stamps tend to yell search me, search me. Some people even go to the trouble of swallowing and then recovering emeralds although obviously, we do not encourage or advise this dangerous practice.