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Diamond Education - GIA Diamond Grading System 

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In 1939 Robert Shipley and Richard Liddecoat went about creating a method of grading a diamonds quality consistently through scientific evaluation. The process they created became the foundation for the internationally accepted and uniformly practiced diamond grading method. Diamonds are examined for their relative purity, or clarity, and the color the stone has by determining it's depth and hue. There are 11 clarity grades and letter assigned color grades from D to Z.


Diamond's Clarity

Diamonds form 90 to 120 miles below the earth's surface in the upper mantle. Due to the chaotic nature of these deep earth conditions as diamond crystals form some foreign elements can find their way into the growth process and become trapped within the stone. These elements become known as inclusions and they are what gemologists examine when determining the clarity of a diamond. Clarity is determined by the inclusion's size, number, position, nature and relief and given a grading as follows:

  • Flawless (F) - No inclusions or external blemishes are visible at 10x magnification.
  • Internally Flawless (IF) - No inclusions and only very minor external blemishes under 10x magnification.
  • Very Very Slightly Included (VVS1-VVS2) - Inclusions within the diamonds are extremely difficult to see with 10x magnification. In VVS-1 stones they can only be seen through the diamonds pavilion, appearing flawless from the face up view.
  • Very Slightly Included (VS1-VS2) - Inclusions are very difficult to difficult to see under 10x magnification.
  • Slightly Included (SI1-SI2) - Inclusions are somewhat noticeable under 10x magnification, and in some cases can be visible without magnification.
  • Included (I1-I3) - These are diamonds with obvious inclusions under 10x magnification and can be visible without the aid of a loupe or microscope, in I-2 and I-3 diamonds inclusions can cause a durability issue for the diamond.

Number designations of these clarity grades (i.e. VS-1;VS-2) indicate a higher and lower classification to each grade with the exception of the flawless categories.

Flawless and Internally Flawless Diamond Very Very Slightly Included VVS1 Diamond Very Slightly Included VVS2 Diamond Very Slightly Included VS2 Diamond Very Slightly Included VS2 Diamond
F and IF VVS1 VVS2 VS1 VS2
Slightly Included SI1 Diamond Slightly Included SI2 Diamond Included I1 Diamond Included I2 Diamond Included I3 Diamond
SI1 SI2 I1 I2 I3


Diamond's Color

A diamonds color is commonly caused by nitrogen becoming absorbed in the crystal during the formation stages. The nitrogen then absorbs a trace amount of color in the visible light spectrum and to varying degrees this causes a diamond to display a slight tint of color. Prior to the current color grading method a confusing system of letter grades using A, B and C was in place, hence the GIA scale begins with the letter D and goes through to Z. Each letter represents a range of known diamond color based on color comparison stones starting at colorless and gradually becoming more saturated with a visible color. The color grading is as follows:


D E F G H I J K L M N O P Q R S T U V W X Y Z
Colorless Near
Colorless
Faint
Color
Very Light
Color
Light
Color

  • D, E, F - Colorless - These are diamonds displaying no color, and are graded according to their level of transparency.
  • G, H, I, J - Near Colorless - These are diamonds displaying a very slight tint of color that is not very noticeable appearing colorless face up.
  • K, L, M - Faint Color - Diamonds that display a slightly more noticeable tint than the near colorless stones.
  • N through R - Very Light Color - Diamonds of this grade display noticeable color.
  • S through Z - Light Color - Obvious color noticeable to an untrained eye.

Colors beyond Z are considered Fancy color, and are graded based on their hue, depth and saturation of color. Diamonds that display colors other than yellow and brown (i.e. blue, pink, green) are considered fancy without this letter system. The fancy color grading system ranges from fancy faint, fancy light, fancy, fancy intense, fancy vivid, fancy deep and fancy dark.


Diamond's Cut

The evolution of diamond cut has been a process in the making for hundreds of years. Since diamond is the hardest element ever found it presents a challenge for diamond cutters to produce a beautiful polished gem. Remember only a diamond can cut a diamond, and with that fact special tools have been designed to facilitate cutting the hardest material known to science.

The round brilliant shape has been the one with the most research done as far as how to bring out the maximum brilliance and fire in the stone. Depth percentage is the ratio between the diamonds diameter and depth measurements, expressed as a percentage this is what tells gemologists how well the diamond will return light to the eye.

Ideal or Premium cuts have depths that ensure the proper angles of reflection occur within the stone so that light entering the diamond through the crown gets returned to the eye. The best way to think of it is as windows and mirrors. The crown facets act as the window, allowing light to enter and exit the diamond while the pavilion acts as the mirrors reflecting this light so it returns through the top.

Different diamond cuts do different things with light, and as of right now there is no Ideal cut diamond when it comes to fancy shapes, although gemological institutions are working on developing a method of evaluating cut on shapes other than round. We are using our own cut quality tables to evaluate cut quality of various diamond shapes.


Diamond's Carat

Carat is the measurement of weight used primarily for diamonds and other gemstones when determining price. In ancient times diamonds and other precious gemstones were weighed on balance scales with the counterweights being carob seeds, this is where the word carat is derived. One carat is equal to 200 milligrams or about one fifth of a gram, this measurement is divided into "points" from one point (0.01ct) to ninety nine points (0.99ct) with each weighing 2 milligrams.

A one carat round diamond with good proportions should measure about 6.50 millimeters in diameter indicating a correlation between the visual size as well as the weight. A diamond is equated at a "per carat" price that is multiplied by the weight to determine the overall cost of the stone.


Diamond's Polish and Symmetry

Polish and symmetry is evaluation of the finished surface on a polished diamond and are rated on a scale from excellent to poor. They are graded under the same 10x magnification standards as clarity and have some moderate effect on the overall price. Stones that have a polish and symmetry of Good, Very Good or Excellent are of a choice quality where great care and expertise went into the finishing of a polished diamond.


Diamond's Fluorescence

Fluorescence is a natural occurrence in some diamonds when exposed to ultraviolet light sources where the diamond appears to glow. The GIA reports that nearly a third of all diamonds graded in their lab every year display fluorescence to some degree. It is rated under long wave ultraviolet light and reported as None, Faint, Medium or Strong. More often the fluorescence appears blue, but can appear as white or yellow as well. The Hope Diamond has a red fluorescence which is considered to be a very rare, as well as a phosphorescence where it continues to glow up to fifteen minutes after the UV light source has been removed which is also an extremely rare and fascinating occurrence.

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