Diamond Grading Guide

On these pages you will learn How to find the best diamond bargains as well as the fundamentals of diamond grading. This is vital to know if you want a good looking diamond at a good price. The key money saving points are in bold type.

Diamond Grading

Diamond color is graded from D-F (colorless) through G-J (near colorless), K-M (faint yellow), N-R (very light yellow) down to S-Z (light yellow). In the K-R range you sometimes get a very light brown called “champagne” and a darker brown called “cognac”, both very attractive. Even when a stone has a visible tint, such as an M color, it can still be very lovely if it has good clarity and cut. Near colorless diamonds will look colorless in the right setting and will save you a lot of money. (More info)

Diamonds also come in a wide variety of other colors, including red, blue, green and a bright yellow known as “canary.” These are graded as Z+ and are known as fancy diamonds. Ones with good color are very rare and can sell for much more per carat than white diamonds.

It is very common for diamonds to be formed in nature with slight imperfections. These are known as inclusions and can come in many forms, including tiny white points, dark dots of carbon, or feathery cracks. The fewer inclusions, the more the stone is worth. A diamond’s clarity ranking is determined by the number, size, type and placement of the inclusions.

The grading ranges from FL (flawless) through VVS (very, very slight imperfection), VS (very slight imperfection), SI (slight imperfection), I1 (imperfect, can be seen with the naked eye) to I3, commercial or industrial grade. Down to SI-2, the inclusions are not visible to the naked eye and are not large enough reduce the Brilliance (sparkle) of the diamond. (More info)

If cut properly a diamond reflects the light back up through the center of the stone to give its characteristic sparkle. A poorly cut stone looks flat like a piece of glass. The quality of the cut is call the “make”, and it ranges from Class 1-Ideal Cut (round diamonds only), Class 2-Well Cut, Class 3-Average Cut to Class 4-Below Average Cut. There are six factors that determine a diamond’s class, the most important being table width percentage and depth percentage. They need to be understood because diamond reports give the factors but do not classify them. For most diamonds, get at least a Class 2 stone or, better yet, a Class 1 to get maximum Brilliance. We give charts that show you how to grade a diamond’s Class. (More info)

Most diamonds 1/2 ct and above come with a diamond report from a gem lab. Often they are fancied up and called “certificates” for marketing purposes, but–no matter how important they look–they are just educated opinions from trained gemologists. The most accurate certificates come from the Gemological Institute of America (GIA) and the European Gemological Laboratory (EGL). Others like IGI are used to sell the junk diamonds found in the mall stores. (More info)

Photographs of diamonds are far from accurate as they need to be enhanced to look good. If you want to save money by buying on-line, learn to read a grading report from a reputable gem lab like GIA or EGL.

An I color, SI-1 clarity diamond with a Class 1 cut will give you a great looking diamond at a bargain price.

Diamond Color Grading

The lack of natural body color is a major factor in determining the value of a diamond. The most expensive are colorless and are graded downward by the amount of yellowish or brownish tint they have.

It is only possible to accurately color grade a diamond if it is unmounted, placed on a white background and compared with a set of standard graded diamonds. A mounted diamond picks up the color of the metal and always looks better set in white gold or platinum. Even then, one can only approximate the color of a mounted diamond within a range of a few grades.

The diamond color grades are as follows:
D, E, F: Colorless. Loose diamonds appear colorless.
G, H, I, J: Near Colorless. When mounted in a setting may appear colorless to the untrained eye.
K, L, M: Faint Yellowish Tint. Smaller diamonds look colorless when mounted. Diamonds of 1/2 carat or more show traces of color.
N – R: Very Light Yellowish Tint and
S – Z: Tinted Light Yellow. These diamonds show increasingly yellow or brownish tints and appear very “off-white”.

Diamonds with distinct natural body colors other than brown or black are considered “fancy diamonds” and some bring higher prices than the finest colorless diamonds. A bright red diamond of less than a carat brought almost a million dollars at auction in 1987.

Discerning the difference in color from D down to H in a mounted stone without direct comparison is very difficult. Yet a large D stone may cost three times an H stone of the same weight. An I (or even J) color grade diamond will look colorless under every-day lighting conditions if mounted correctly, and will save you a lot of money.

Because of other factors that contribute to the beauty of a diamond, there are many beautiful stones below an M color such as a very light yellow called “champagne” and a darker yellow/brown called “cognac”.

In diamonds over one carat, the color effects the value more than in smaller stones as it is more apparent. But choosing a lower color grade will reduce the price, and there will be little, if any, visible difference when the stone is mounted.

Diamond Clarity Grading

A diamond s clarity grade is actually a flaw-grade and refers to the tiny imperfections present when the stone was originally formed by nature. If no flaws can be seen under 10X magnification, such as with a diamond loupe, it is considered “flawless”.

There are 13 classes of flaws internal (inclusions) and external (blemishes), but the most common are dark spots of foreign material, tiny internal cracks called “feathers”, and external nicks or chips.

The diamond clarity grades are as follows:
FL: Flawless. Cannot be seen with a 10X diamond loupe.
IF: Internally Flawless. Has tiny nicks or scratches that can be polished out.
VVS1, VVS2: Very, Very Slightly Included. Very, very difficult for a qualified observer to see under 10X magnification.
VS1, VS2: Very Slightly Included. Very small inclusions, very difficult to see by a qualified observer.
SI1, SI2: Slightly Included. Can be seen fairly easily by a qualified observer with a 10X loupe, and in some cases without magnification.
I1, I2, I3: Imperfect. Inclusions can be seen with the naked eye, but can be desirable stones at a much lower cost if they are brilliant and lively. Because I3 is the lowest grade used, be on the lookout for industrial grade diamonds not suitable for jewelry that have been classified I3.

FL and IF diamonds are extremely scarce and expensive, so are rarely used in jewelry. VVS stones are rare and priced at a premium, but VS diamonds are more readily available in good color and cut. With SI and I1 stones you find your bargains in good looking diamonds, and I2 should be the bargain hunter s choice for earrings that cannot be viewed up close. With SI and I1 stones you find your bargains in good looking diamonds, and I2 should be the bargain hunter’s choice for earrings or pendants that are difficult to view up close, as they are priced very reasonably. If well cut with a Class 1 Premium cut grade, they are beautiful.

Clarity grades dramatically affect the value of a diamond, but down to I1 have little effect on its beauty.

Clarity enhancement techniques are being used today and should be disclosed by reputable jewelers. The most common are lasering to remove black inclusions, fracture filling to hide cracks and heat or radiation treatment to lighten or change the color.

The final test is whether or not you get a good looking stone at a fair price. We give a money back guarantee with every diamond we sell. (Go next to Diamond Cut Grading)

Diamond Cut Grading

A rough diamond looks like any other rock until it is “cut” into many facets at optimum angles to produce maximum brilliance (sparkle) and fire (reflected colors). The quality of the cut is known as the “make”.

In 1919 Marcel Tolkowsky developed the formula for the round brilliant cut which has become the standard or “ideal” cut for diamonds. Since then there have been various modifications and disagreement over what constitutes the true “ideal” cut. However, the Gemological Institute of America (GIA) has developed the following guidelines for grading the make of round brilliant cut diamonds only.

The Table Size % is the ratio of the table diameter to the girdle diameter. The Depth % is the ratio of the distance between the table and the culet to the girdle diameter. These are the two most important factors in determining the grade of a diamond’s cut.

This is the factor that contributes the most to a diamond’s beauty. Even if a diamond is brownish and has visible inclusions, if it sparkles well it is a thing of beauty. Print the tables below and use them to find a diamond with a Class 1 or at least a Class 2 Cut grade and you won’t go wrong.

Round Brilliant Cut Diamonds only.

KEY FACTORS Class 1
Premium Cut
Class 2 Well Cut Class 3 Cut Average Class 4 Cut Below Avrg
Table Size
53-60% of diameter
61-64%
65-70%
over 70%
Depth
58-63% of diameter
57-64%
56-66%
under 56% over 66%
Crown Angles
34-35 degrees
32-34 degrees.
30-32 degrees
less than 30 degrees
Girdle Thickness
medium – slightly thick
thin-thick
thin or very thick
knife edge or very thick+
Polish & Symmetry
very good – excellent
good
fair
poor

More detailed charts were developed by David Atlas for fancy cut diamonds and are used by Accredited Gem Appraisers, D. Atlas & Company, Inc. and the National Association of Jewelry Appraisers. Simplified versions for these charts are shown below.(Revised: 3/02)

Princess Cut Diamonds

KEY FACTORS Class 1 Cut Premium Class 2 Cut Fine Trade Class 3 Cut Average Class 4 Cut Below Avrg
Table Size
60%-71% of diameter
58%-77%
53%-85%
Below 53%
Above 85%
Depth
64%-75% of diameter
58%-80%
56%-84%
Below 56% Above 84%
Crown Height %
8.5%-11%
6.0%-13%
4.0%-17.5%
Below 4.0% Above 17.5%
Girdle Thickness
thin-med or med.-thick
thin-thick
very thin – very thick
extra thin – extra thick
Polish & Symmetry
good – excellent
fair -good
fair-good
poor to fair

Pear, Marquise, Heart, and Oval Cut Diamonds

KEY FACTORS Class 1.
Premium Cut
Class 2. Fine Trade Cut Class 3. Average Cut Class 4. Below Average
Table Size
54%-61.5% of diameter
52%-64%
50%-70%
Below 50% Above 70%
Depth
59%-63% of diameter
58%-65.4%
46%-71%
Below 46% Above 71%
Crown Height %
12.5%-15%
11.1%-16.5%
8.7%-18.4%
Below 8.7% Above 18.4%
Girdle Thickness
thin-med. or med.-thick
thin-thick
very thin to very thick
extra thin to extra thick
Polish & Symmetry
good to excellent
good to excellent
good to fair
fair to poor
Length: Width Ratios
Class 1 & 2
Pr. 1.5-1.75 M.1.75-2.25
Class 1 & 2Ht..98-1.02 O.1.33-1.66
Class 3 & 4Pr.1.26-1.99 Mr.1.51-2.49
Class 3 & 4Ht.0.91-1.24 Ov.1.26-1.74

Emerald and Radiant Cut Diamonds

KEY FACTORS Class 1. Premium Cut Class 2. Fine Trade Cut Class 3. Average Cut Class 4. Below Average
Table Size
60%-64.1% of diameter
58%-69%
53%-76%
Below 53%
Above 76%
Depth
60%-65% of diameter
58%-69%
56%-78%
Below 56% Above 78%
Crown Height %
11.9%-15%
11.1-16.2%
8.5%-18.5%
Below 8.5% Above 18.5%
Girdle Thickness
thin-med or med.-thick
thin-thick
very thin to very thick
extra thin to extra thick
Polish & Symmetry
good – excellent
fair-good
fair-good
poor to fair
Length-Width Ratios
Emerald Cut: 1.26-1.99

There are other grading systems such as “A, B and C” and a large variety of opinions that align loosely with the above charts. We have used diamond appraisers manuals to prepare these charts, so consider them accurate.

Recently, GIA has started putting the cut grade or the make for round brilliant cut diamonds on their certificates. For other diamonds or grading certificates, use the tables above to ensure you get a good looking one.

Diamond Carat Grading

Carat (ct) is a measurement of weight, not accurately “size”. There are five carats to a gram. A 1 ct sapphire is smaller in size than a 1 ct diamond because it is heavier. There are 100 points to a carat, so a 50 point diamond weighs 1/2 of a carat or 0.50 ct.

Diamond prices are usually quoted per carat. Therefore a 0.50 ct stone quoted at $2,000 per carat would cost $1000. As the carat weight increases for the same quality of diamond, the price per carat goes up. So a 1.00 ct stone of the same quality might cost $4,000 instead of $2000 per carat.

Also the price per carat will jump as you approach the next higher carat weight. Therefore a 0.95 ct diamond of the same quality as the 1.00 ct stone above might cost $3,500 per carat or $3,325, but look almost as large.

The term spread refers to the size a diamond appears to be in a setting, based on its diameter. So a 0.90 ct stone with less depth might look the same size as a perfectly cut 1.00 ct diamond, but may have less brilliance because it is cut shallower.

This is why it is important to understand the basics of color, clarity, cut and carat when reading a diamond grading report (sometimes called a certificate). All four factors influence both the beauty and the price of a diamond. Evaluating the value of a diamond by color and clarity alone can lead to a costly mistake because the quality of the cut is a very major factor governing a diamond s appearance. Evaluating a diamond by color and clarity alone can lead to a costly mistake because the quality of the cut is the major factor governing a diamond’s appearance.

A proper diamond report should give the following information:
1. The date issued; 2. Who issued it; 3. Identify it as a real diamond; 4. The exact carat weight; 5. The dimensions including narrowest and widest diameter and depth; 6. Proportioning–table and depth percentage; 7. Color and clarity; 8. Polish and symmetry; 9. Girdle thickness and crown angle.

The final test is the overall appearance. Every diamond will have its faults, and even with major faults a stone can be very beautiful. If it is a good looking diamond and fits your needs, buy it.

Photographs of diamonds tell you nothing except the shape and position of inclusions invisible to the naked eye so are not important. They have to be enhanced to look good, so do not show the important factors needed in choosing the right diamond. Only a diamond grading report gives you these. So learn to read one before you buy.

Here s the link to search our over 50,000 Loose Diamond List to find a best buy in the kind of diamond you want.

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