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.

Color rating diamond

King of diam — Sat, 19 Sep 2009 22:10:16 +0000

The second C used in rating diamonds is color. Diamonds come in literally
every color in the rainbow and while a few specialty colored diamonds are
extremely valuable because of their deep hues and unique color characteristics,
these are the exceptions rather than the rule. In general, the closer a stone
is to possessing no color, that is, to being colorless, the more the stone is
worth.
In order to establish the transparency or lack of color in a diamond, the
loose stone is placed on a pure white background under a white light. There
are special lights sold with adjusted color temperatures for this viewing or
some people prefer to use the soft north sunlight when trying to view the
color of a diamond.
In color rating as in clarity rating, the dazzling brilliance and fire of a
diamond are the viewer’s natural enemy. They will confuse the eye and care
must be exercised to not become jaded or tricked, but rather to view each
characteristic individually and in comparison to other stones or photographs
of stones.
The most accepted color grading system is that again of the GIA. Their system
is judged by using a series of master stones sold by the GIA or their
representatives that establish hues and tints and can be laid side by side
with the stone in question in order to view how “white” the stone really is.
If at all possible, it is certainly worth one’s time to visit a large gem
dealer with the intent or apparent intent of purchasing a goodsized stone and
ask to see a master set and become used to judging the color on several stones
until you have a feel for the concept of whiteness, transparency and hues.
Technology has now produced a practical and inexpensive (comparatively) method
of possessing your own diamond master stones. These stones are available in all
colors D through Z on the GIA scale and are excellent to have on hand to
compare with any other stone you may be considering purchasing in order to
rate the new stone. These stones are color correct because they’re created to
be exactly the color they’re supposed to be.
How can this be cheap? The stones are not diamonds. They’re CZ’s, cubic
zirconia. These CZ stones look like diamonds, act like diamonds, smell like
diamonds and can be matched to a real diamond in order to compare colors with
an extreme degree of accuracy.

There’s also a device known as a color meter which electronically measures the
color or lack of color in a stone. This meter is quite accurate although
fairly hard to come by unless one is a member of the Gemological Institute of
America.
The GIA color rating system has been established using alphabetical
nomenclature. The stones are rated from pure (totally colorless) down through
a sliding scale to yellow, which is the least valuable stone. The GIA color
rating system starts with the letter D and progresses through the alphabet as
shown below to Z, which would be very yellow.

A B C D E F ) Colorless
G H I J ) Near Colorless
K L ) Faint
M ) Yellow-White
N O ) Very Light Yellow
P ) Light Yellow
Q ) Yellow
R S T U ) Light
V ) Yellow to Fancy
W ) Fancy
X Y Z ) Yellow

After the letter Z, indicators are used to suggest the stone is more valuable
because of its hue; i.e., a “fancy” color. As you can see from the above chart,
D, E and F stones are considered completely colorless. G, H, I and J are near
colorless stones and take a lot of practice for the amateur to see any color
at all, while after J the stones begin to pick up a small tint of yellow that
is noticeable to practiced gemologists.
To correctly grade a gemstone, the stone must be loose, not in a setting,
should be on a perfectly white background, should have a white gem quality
temperature light and should be viewed from the rear of the stone. In other
words, the stone should be upside down Iying on its table. It is also
extremely helpful to have stones of known color grades nearby for active
comparison.
Never attempt to judge the color of a diamond when it is set in any kind of
setting, be it earring, ring, or whatever as it is strictly impossible to
judge the color of a mounted stone that is taking on hues and tints from the
mounting itself.
Color is a very important consideration in choosing investment quality
diamonds and, in fact, the differences in large sizes such as one carat and
over from a D to an E color (again these are the top rated stones and are both
considered colorless to the naked eye) can be double the price between these
two grades.

Diamond Jewelry King » transparency

Rubis

Color rating diamond