Diamond Grading Information


 

     There is no great mystery in HOW TO BUY A DIAMOND.  In the 10 minutes it takes to read the following information, you can possess as much, if not more diamond knowledge than your average diamond sales person (many of which have never had any formal training). Diamond pricing is derived from what is known as the "4 C's", which is Carat, Color, Clarity and Cut. All 4 of these terms must be looked at individually when looking to purchase a diamond for yourself or for the one you love in order to determine the TRUE grade of any Diamond.

CARAT

COLOR

CLARITY

CUT

DIAMONDS COLORED GEMSTONES FINE JEWELRY HOW TO ORDER

Cost Factors for Diamonds

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The following information assumes the Gemological Institute of America (G.I.A.) grading system. This is the worlds most recognized system of evaluating a diamonds quality and value.  Each grade describes a different aspect of the diamond and it is only the sum total of all these characteristics which will determine the true or real value of any particular diamond gemstone.
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CARAT
CARAT is a measurement of weight (1 carat = 1/5 of a gram). A diamond weight is a very important factor to its cost. The term "carat " originated from the seeds of the carob tree. These carob seeds are extremely uniform in weight and this made them the ideal weight unit for the ancient gem traders.
This weight (one carob seed) as later standardized to be 1 carat, or 1/5th of a gram, hence a five carat diamond equals 1 gram and 155.51 carats equal one ounce.  The one carat weight is then broken down into 100 equal parts called "points"; 75 points equal 3/4 of a carat, 50 points equal 1/2 of a carat, etc. The significance of the weight is like the other quality grades. It is important to understand that the weight of a diamond and its physical size are two different things.  Even if the only difference between the two diamonds is .01 carat or 1 point.  Take for example, two (2) SI-1, H quality grade 1.00 carat diamonds to show the vast difference in value that the cut will make.  One of these diamonds could have the Ideal 6.5 millimeter diameter size one would expect to see in for a 1.00 carat diamond.  In the other example, the second 1.00 carat diamond may have only a 5.5 millimeter diameter.  Because of this one millimeter diameter size difference, and yet the same carat weight, the smaller diameter diamond would be worth as much as 80% less than the Ideal cut diamond of the same weight and quality grade.  These value differences will vary depending upon the size and quality grade of the diamond you may be interested in.  This leads us to the fourth quality grade which is the diamonds cut.  Every Diamond belongs in a weight grouping class for a range of weight where the prices per carat for each Color and Clarity group combination are listed.  The main reason for this is obviously due to rarity in nature, but current market conditions at any specific time plays a very important role.  Some sizes and shapes fall in and out of demand due to what is fashionable or considered affordable in society.  Because of this, some size groupings for a given shape may have a  higher demand and price per carat than one expects, given its rarity in nature.

So to simplify, a diamond in the 1 carat class (1.00-1.49) usually costs more per carat than a diamond less than 1 carat in weight (0.90-0.99).  A diamond that is 1 full carat in size, has a higher demand, which causes it to be priced higher.  The result is rough stones that could possibly have been cut into beautiful smaller stones are usually cut into not so beautiful 1 full carat stones to get into the higher price range.   There are other factors and trade-offs this is just a simplified answer to the reason the cost per carat goes up as the size goes up..

CARAT

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COLOR

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COLOR GRADING begins with the letter "D". Why does the GIA color grading system start at D? Before GIA introduced the GIA D-Z Color Grading Scale, a variety of other symbols were loosely applied throughout the industry. Not only were A, B, and C used without clear definition, but some dealers, taking a cue from the poultry business perhaps, started grading their diamonds double A (AA). Other systems used numbersóboth Arabic (0, 1, 2, 3) and Roman (I, II, III). Most dubious of all were systems that relied on descriptive terms like "gem blue" or "blue white." Terms like these are notoriously susceptible to misinterpretation. So the creators of the GIA Color Scale wanted to start fresh. They wanted symbols that would not have any association with earlier systems. Thus the GIA scale starts at the letter D. There may be some people still clinging to other grading systems, but no other system has the clarity and universal acceptance of the GIA scale.

  • D-F  - the finest & brightest colorless diamonds, usually for the discriminating customer who can afford the most beautiful and the rare.
  • G-H - are very white & bright face-up colorless diamonds that are not as expensive, and when mounted in jewelry it is difficult to see the a difference between these and the higher grades.
  • I-J   - are are not quite as bright or have very slight hardly noticeable tint.
  • K-L - have a slight tint even the average person will begin to notice.
  • M-Z - the color will be noticed.

  •     Each grade can have a 10-15% variance in it's price range for a given size group, down to M, and then it changes again depending on the Hue & Color for the Fancy Colored Diamonds.

        Diamonds occur naturally in all spectral colors, from red to blue, however the most commonly occurring colors are yellow and brown. The amount of color a diamond possesses is graded by an alphabetical scale D through Z. Color & Cut are the two factors that influence a diamond's beauty the most.

       Color should reflect one's tastes and budget.  i.e.: You may be able to go with a higher color grade and lower clarity grade to suit your taste and stay within budget.

        Diamonds of a colorless grade in the D-F range are much more valuable than diamonds in the L-P range because of the rarity of these colorless diamonds. This is not to say that the diamonds in the lower color range are not pretty, they can have just as much brilliancy and sparkle but with a stronger color tone. The effects of color to the cost of a diamond can be dramatic. Two diamonds of the same weight, clarity , size and shape can have a cost difference of over 100% for the difference between an F body color to a J body color . Color can only be graded accurately if the diamond is un-mounted or "loose" and it is highly recommended that the diamond be independently certified by an accredited LAB (GIA, AGL, EGL, etc) for its color as well as the other following quality grades. The color of your diamond will be simply a matter of personal taste and if you don't like the color - just plan to spend more money!
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        Another color factor to consider is Fluorescence, properly called photo-luminescence.  Fluorescence is caused by a trace amount of the element boron found in the diamond. It is activated by UV light. Fluorescence in a diamond is usually described on a certificate (GIA, AGL, EGL, etc.) as None, Faint, Medium,
    Medium blue, Strong, Strong blue and Intense Blue. Other colors of fluorescence do occur, yellow and white for example (try to avoid them), but it is the blue we are most commonly involved with.  In the old days people used to come looking for the perfect "blue-white" diamond. The blue referred to the fluorescence and the white to the diamonds body color.  Some people think diamonds exhibiting fluorescence is out of fashion, but Gems and Gemology (put out by GIA) GIA states that typically fluorescence is a plus in diamonds. Most people feel that fluorescence is beautiful and rare in a diamond, so in a few years fluorescent diamonds may be back in fashion and will demand a premium.  If you want a diamond that exhibits fluorescence be sure you examine it under all light conditions, especially direct sunlight and a jewelers black light, since some fluorescent diamonds will actually become hazy in the sunlight and others will glow in a black light environment (including a dance floor) if the fluorescence is Intense (and sometimes Strong).  With Strong or Intense fluorescence I advise you to fully examine the stone, each diamond will exhibit its own traits, and in many cases these traits will have a positive effect, often causing the diamond to have a little "extra life" in the sunlight.  If you are dealing with a diamond of H color or lower, fluorescence is normally a plus, and will increase the diamonds beauty and desirability.
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        So to sum things up, examine any diamond  with fluorescence, which you are looking at purchasing, under all light forms and make up YOUR mind for YOURSELF, as to whether it is a plus or minus.

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    COLOR GRADING SCALES
    COLORLESS D EXCEPTIONAL WHITE+
    E EXCEPTIONAL WHITE
    F RARE WHITE+
    NEAR COLORLESS G RARE WHITE
    H WHITE
    I VERY SLIGHTLY TINTED WHITE
    J SLIGHTLY TINTED WHITE
    FAINT YELLOW K TINTED WHITE
    L
    M BEGINNING OF TINTED COLOR
    VERY LIGHT YELLOW N TINTED COLOR
    O
    P
    Q
    R
    LIGHT YELLOW
    Y and Z could also be
    labeled FANCY YELLOW
    S TINTED COLOR+
    T
    U
    V
    W
    X
    Y
    Z
    BROWNISH
    "CHAMPAGNE" (Argyle Mine Term)
    C1 - C3 TOP LIGHT BROWN
    C4 - C6 FANCY LIGHT BROWN TO
    FANCY  BROWN
    CANARY YELLOW
    GREEN
    BLUE
    PURPLE
    PINK
    RED
    FANCY LIGHT FANCY LIGHT COLOR
    FANCY FANCY COLOR
    INTENSE (VIVID) FANCY VIVID COLOR
    GIA Color Grading Scale


    CARAT

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    CLARITY

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    CLARITY

            In plain terms clarity is simply how much "stuff " (inclusions) is inside the diamond crystal. The less "stuff " the more they cost. This again because of rarity by lack of imperfection. Most all of the diamonds mined have inclusions that are visible to the unaided eye. A typical retail jeweler may never sell a flawless clarity grade diamond!

            This scale ranges from F to I-3. This entire scale can be divided in half, with diamonds that you can visually see the imperfections to the unaided eye, and diamonds that require 10 power magnification to see the imperfections. This division is at the I-1 clarity grade to the SI-2 clarity grade. The I-3 clarity grade will generally contain enough imperfection to dramatically reduce the amount of brilliancy and sparkle and should not be considered for "fine jewelry". However there can even be a good , as well as bad I-2 or I-1 clarity grade diamond. As an example a good I-1 clarity grade diamond would have an imperfection to the side which would be eye visible, however after being set would be covered by a prong or other feature of the setting. The less desirable I-1 clarity grade diamond would possess a very similar inclusion however because of its location would not be able to be hidden. An eye visible inclusion such as this would later prove to be a distraction to the beauty of the diamond. As with the color of the diamond , clarity is very much personal taste and if you donít like the number of imperfections - just plan to spend more money!

    • FL - FLAWLESS describes diamonds in which a gemologist under favorable lighting conditions, cannot see any inclusions at ten power magnification.
    • IF - INTERNALLY FLAWLESS describes diamonds which have no internal characteristics observable under the the same conditions as (FL), but which have minor surface blemishes that do not penetrate the stone.
    • VVS1 & VVS2 - VERY, VERY SLIGHTLY INCLUDED describes diamonds that have very, very small inclusions which are difficult for a gemologist to see at 10x magnification.
    • VS1 & VS2 - VERY SLIGHTLY INCLUDED describes stones with very small inclusions which can be difficult to observe with 10x magnification.  Inclusions are still not visible to the unaided eye, except on larger stones or occasionally with Emerald Cut diamonds.
    • SI1 & SI2 - SLIGHTLY INCLUDED describes stones with small inclusions which are usually obvious when viewed with 10x magnification.   Inclusions are difficult to see with the unaided eye, except on larger stones or occasionally with Emerald Cut diamonds.
    • I1, I2, & I3 - IMPERFECT describes stones with medium to large inclusions (Piques) which are usually obvious to a gemologist with the unaided eye.  Inclusions are generally easy to identify with the unaided eye, especially on larger stones as well as with Emerald Cut diamonds.
    CLARITY GRADING SCALES
    FL FLAWLESS
    IF INTERNALLY FLAWLESS
    VVS-1 VERY, VERY SLIGHTLY INCLUDED
    VVS-2
    VS-1 VERY SLIGHTLY INCLUDED
    VS-2
    SI-1 SLIGHTLY INCLUDED
    (EGL uses SI-3 before I-1)
    SI-2
    I-1 IMPERFECT or PIQUE
    I-2
    I-3
    CLARITY GRADING CHART


    CARAT

    COLOR

    CLARITY

    CUT

    DIAMONDS COLORED GEMSTONES FINE JEWELRY HOW TO ORDER

    CUT

       The Cut is the most important characteristic of a diamond. This factor determines how much light when entering the diamond from above will be reflected and refracted back out of the gem to the eye of the observer as illustrated in the picture below.  In other words how pretty the diamond can be is decided by the cut.  For the consumer it is fairly easy to determine in general terms if a round brilliant cut diamond is well cut or proportioned.  The first and easiest characteristic to evaluate is to compare the diamonds weight with the proper diameter size listed in the "Size to Weight Ratio Chart" below.  If a diamond has a 1.00 carat weight, then its proper diameter size should be 6.5mm. This is the first and easiest characteristic to evaluate.  The rest of the characteristics, that are equally important, such as depth% and table%, polish, symmetry can also easily be determined by comparing the information in the tables below with the information provided on the certificate of the diamond you are interested in.
     

    Size to Weight Ratio Chart

          Generally, if the size to weight ratio are cut correctly the entire bottom side of the diamond is turned into a mirror, reflecting all of the light back out of the top side of the diamond.  If the cut has been poorly done even the highest quality grade diamond will look lifeless. As an example, in the illustration below, lets assume that each of these diamonds has a carat weight of 1.00 carats.
     
     

    Ideal Cut -
    Shallow Cut -
    Deep Cut -

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            As in this illustration the "shallow cut" (7.0mm) diamond has been cut too wide and shallow for its weight and the light will escape out the back or pavilion of the gem, also note, this stone faces up as a 1.25ct diamond (here you could get a larger looking diamond for a cheaper price but you will sacrifice brilliance and fire). In the "ideal cut" (6.5mm), the diamond has been correctly cut and the light entering the diamond will return to the eye.  The "deep cut" (6.0mm) diamond has been cut too narrow and deep and again looses the light out the pavilion, also note, that this stone will only face up as an 0.80ct diamond or approximately a 3/4ct.  Diamonds are cut by the manufactures to yield the greatest amount of carat weight from the rough, which they also buy by the carat.

            It is therefore in the best interest of the cutter to cut for weight, not for proportions. Unfortunately, consumers are generally not informed about cut and its relation to value, cost, and especially it's BEAUTY, although, it is a BIG factor in the overall value of the diamond.

            Now let's evaluate the cut.  This includes the depth percentage, table percentage, crown angles, crown height, girdle thickness, pavilion depth, culet size, finish, symmetry and polish.  All of these factors are just a simple comparison of the data in the "Typical Diamond Proportion Analysis Chart" below, and with the laboratory certificate of the diamond you are interested in.  When ordering your diamond, we will be happy to explain all of these individual quality grades in more detail.  The Proportion Tables below will give you the industry parameters for Round brilliant cut diamonds as well as Marquise, Pear, Emerald, Princess and Ovals. Understanding the cut of a diamond is very important, as two diamonds with the exact same quality grades can have a 30% difference in cost because of the cut.
     

    Typical Diamond Proportion Analysis Chart

    Diamond Anatomy


     

     

    Proportions for Round Brilliant cut diamonds

    Components Ideal Proportions Near Ideal Proportions
    Total Depth 58.7 - 62.9% 58.0 - 62.0%
    Table Diameter 53.0 - 60.0% 58.0 - 64.0%
    Girdle Thickness medium - sl. thick thin to thick
    Crown Angles 34 - 35 degrees 32.0 - 36.4 degrees
    Pavilion Depth 42.5 - 43.5% 42.0 - 46.0%
    Pavilion Height 15.0 - 17.0% 13.5 - 17.5%
    Polish Vgood to excellent good
    Finish Vgood to excellent good

     

    Proportions for Emerald, Radiant, and Princess

    Components Ideal Proportions Near Ideal Proportions
    Total Depth 60.0 - 65.0 58.0 - 69.0%
    Table Diameter 61.0 - 65.0% 59.0 - 68.0%
    Girdle Thickness thin to thick thin to thick
    Crown Angles 32.0 - 34.0degrees 34.5 - 36.0degrees
    Polish Vgood to excellent good to excellent
    Symmetry Vgood to excellent good to excellent
     The ideal length to width ratio for Emerald and Radiant cuts are 1.3/1,
    ie: 9mm x 7mm, or, 7mm x 5mm, etc.
    The ideal length to width ratio for Princess cut is 1.0/1.0, +/- 10%,
    ie: 6mm x 6mm to 6mm x 6.60mm
    Ratios are non-determining factors for these cut types

     

    Proportions for Marquise, Oval, Pear & Hearts

    Components Ideal Proportions Near Ideal Proportions
    Total Depth 59.0 - 63.0% 58.0 - 65.4%
    Table Diameter 60.0 - 63.0% 56.0 - 64.0%
    Girdle Thickness thin to sl. thick thin to thick
    Crown Angles 33.0 - 34.0 degrees 31.0 - 36.0 degrees
    Polish Vgood to excellent good to excellent
    Symmetry Vgood to excellent good to excellent
    The ideal length to width ratio for Marquise cut diamonds from 2/1,
    ie: 10mm x 5mm
    The ideal length to width ratio for a Pear or Oval cut is 1.5/1,
    ie: 6mm x 4mm
    The ideal length to width ratio for a Heart cut is 1/1,
    ie: 6mm x 6mm

     

    Dollar Cost effects of Fluorescence

    IF to VVS grades VS to SI grades I-1 to I-3grades
    D-F colors strong -10%

    moderate -5%

    weak -0%

    strong -5% to -10%

    moderate 0% to -5%

    weak -0%

    -0%
    G - J colors strong -5% to -10%

    moderate -0% to 5%

    weak -0%

    strong -0% to -5%

    moderate -0%

    weak -0%

    -0%
    K- M colors strong -0 to -5%

    moderate -0%

    weak -0%

    strong -0%

    moderate -0%

    weak -0%

    -0%

     


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