Diamond Education

Once you’ve gotten this far you have already probably heard about the “4 C’s” of diamonds.   The diamond grading class offered by GIA is a several month course so this synopsis is very basic just to give you and idea where to start.

Carat, Color, Clarity, and Cut.  

The sum of the 4 C’s will ultimately determine the “5th C” …Cost or Cash.  We will give you a brief overview to help you better choose a diamond that is right for you.  But keep in mind, we highly recommend you speak with one of our diamond experts to help you pick the diamond that is best for you and keep in your price range.

Don’t let someone convince you that you need a particular quality.  Everybody has different needs and it is our commitment to find you the diamond that fits you best.

Most online companies don’t own or even see the diamonds they sell. They just upload a list from some vendors and mark them up.  It is best to speak with an expert that is holding the diamond, can see it and describe it while speaking with you.  There are many skills required to acurately read a certificate and much of what you actually see in the diamond is not represented on paper.  Remember, you are not buying a certificate, you are buying a diamond!


Carat is the easiest to explain because it refers to the weight of the diamond measured in carats.  To measure this we place the diamond on a scale.  One carat is 0.2 grams. It takes almost 142 carats to equal 1 ounce. One carat has what we refer to as 100 “points.”  Therefore, a quarter carat would weight 25 “points.”  A half carat 50 “points.”  And a three quarter carat 75 “points” and so on.


Color is what we refer to as the actual visible “tint” of the diamond.  The highest color and most rare is colorless.   Most diamonds sold in retail stores are near colorless to faint or light brown or yellow.  The rating scale starts at D and goes through the alphabet to Z and beyond.  Those diamonds with a strong color, past Z on the scale are referred to as fancy color.   Diamonds come in a variety of colors such as yellow, blue,green, orange, pink and red, but are extremely rare.  With the exception of the rare fancy colors, colorless diamonds command the highest prices.

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Clarity is the degree to which a diamond is free of blemishes and “inclusions.”  Inclusions are internal “imperfections” in the diamond. Some inclusions are caused by conditions present when the diamond was formed, others during the cutting process. Since nature makes nothing absolutely pure or perfect those diamonds with few inclusions are rare and command a higher value or price.  The industry wide scale ranges from the low end of “gem quality” diamonds I3,  to the best flawless.

Most diamonds have eye visible inclusions.  These range from easily visible, clarity grades I2-I3, to barely eye visible I1.  One must also keep in mind the size of the diamond also greatly influences this generalization.    The industry uses 10x magnification in grading clarity in diamonds.

I1-I3 (imperfect), this is the broadest of all categories.  Most gem quality diamonds fall into this range.  This quality basically means you can visibly see imperfections without magnification.  How easy depends on the stone.  However, the lower qualities I2-I3 have so many inclusions they will generally not be shiny.

An I1 stone may not be bad quality and, in some cases may be considered “eye clean”.  The eye clean stones are referred to in the industry as SI3.   In fact, I1-I2 is mostly what you find at retail jewelry stores.  The diamond may still have good to great color, lots of shine and sparkle but if you look very closely you may see a tiny inclusion.  Many customers don’t notice it until after the purchase but it may good value for those who want a big bang for the buck!

SI (Slightly Included), refers to stones that under 10x magnification have noticeable or fairly noticeable inclusions but are generally “eye clean.”   Eye clean means that holding a diamond and looking at it without magnification on a hand you will NOT see visible inclusions.  Depending on the size of diamond, type and locaiton of inclusion some SI graded diamonds may not be 100% eye clean.  Most of our merchandise is SI or  better.  This is a quality diamond that can be compared to higher quality.  The only difference is under magnification.

VS (Very Slightly included), and inclusions are noticeable, by an expert,  under 10x magnification but are minor and small in appearance.  Unless you are  using a microscope and the inclusions are pointed out, the average buyer will probably not see inclusions even under a 10X loupe. This is very high quality.

The highest grade next to flawless isVVS (Very Very Slightly included).  Diamonds graded VVS contain extremely small inclusion difficult for even skilled graders to see under 10x magnification.  You will no doubt not see ANY inclusions under a 10x loupe and may not even see any under a microscope.  This is EXTREMELY high quality.  Only a fraction of 1% of all diamonds acheive this grade.

The most rare clarity is IF (Internally Flawless).  These are classified as being free of any internal imperfection under 10x magnification.  This is extremely rare and very expensive.  We do not suggest an IF stone because even normal wear can cause this type of diamond to lower in clarity by chipping or abrading.

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Cut refers not to the shape of the diamond but to the proportions to which the stone was polished.  This is a touchy subject because it is difficult to measure “brilliance” in a diamond.  However, there are several theories behind cutting the “ideal” diamond such as Tolkowski but grading cut and ranges have changed several times since the induction of the rating.

How Does Cut Effect the Diamond
This is  hard subject to explain. What “cut” means is basically “proportions”. The idea being if I cut the diamond to mathematically maximize the brilliance of the diamond it will be more brilliant. What is not explained is that it may maximize the brilliance of that particular rough (diamond) in cutting, it does not mean that the particular diamond will be more brilliant than one cut with mathematically inferior proportions. So, I would be carefull about what I read online about cut because, theoretically it makes mathematical sense, but don’t take it as an absolute truth.

The Ratings
The AGS (American Gem Society), has come up with a “cut grade” with all their diamond reports.  Based upon this theory and others we can conclude that the best cut diamonds fall into a range.  AGS grades their perfectly cut diamonds 0 on a scale of 0 – 10.  AGS ideal 0 cuts are extremely rare and consequently will cost much more.   Very fine cut diamonds, AGS 1 and 2 grades,  are also rare but also exhibit extreme brilliance and provide a great value.

GIA and other labs also have their cut grading scales ranging from excellent, very good, good, fair and poor.

gia cut grading

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The cut ratings include a number of factors and here is a list of some of them.

Depth % 59% – 62.5% 57% – 63%
Table % 52.4% – 57.5% 51.4% – 63%
Girdle Thickness Thin to Medium Very Thin – Thick
Culet Size None – Medium None – Medium
Polish Excellent Excellent – Good
Symmetry Excellent Excellent – Good
Florescence None – Faint None – Medium


Cut in fancy shapes

Since fancy shapes are not symmetrical like the round diamond no information has been published as to the “ideal cut” fancy shape diamond.  However, the industry , as well as our experts, has combined information to determine a range for well cut fancy shapes.  This is based on analyzing several thousand stones over years of experience.   A well cut fancy shaped diamond will produce outstanding brilliance.  There are other cut factors in fancy shapes, but here are a few to consider.


                                     EMERALD     PRINCESS      MARQUIS       PEAR

Depth % 65% – 75% 65% – 80% 59% – 70% 60% – 70%
Table % 50% – 75% 65% – 80% 52% – 60% 55% – 65%
Girdle Thickness Very thin-Thick Very thin-Thick Very thin-Thick Thin – thick
Culet Size None-Medium None-Medium None-Medium None – Medium
Polish Excellent-Good Excellent-Good Excellent-Good Excellent – Good
Symmetry Excellent-Good Excellent-Good Excellent-Good Excellent – Good
Florescence None-Medium None-Medium None-Medium None- Medium
Length/Width Ratio 1.3-1.65 to 1 1-1.3 to 1 1.7-2.2 to 1 1.4-1.8 to 1

What is Florescence?

Houston Diamond District - Diamond EducationFlorescence is the impact of ultra violet light on the diamond.  1/2 of all diamonds have some sort of florescence, from very faint to very strong.  This means that under ultra violet light the diamond will glow blue.

Does this have an impact on value?  Some times.  It depends on its noticeability.  Diamonds of high color, sometimes appear milky or cloudy when they have strong florescence.  But not all the time.  The other circumstances when it is noticeable is under direct sunlight, which has ultra violet light in it.  Those diamonds which appear blue under sunlight would be lower in value.

On the other hand florescence may add value to a diamond of lower color as it gives the diamond a whiter, brighter appearance.  Diamonds with as high as H color and lower sometimes appear whiter with some degree of florescence.

Here is a chart as to how the industry discounts florescence.  As you can see those diamonds with the higher quality and more strong florescence have the largest discounts.

Remember, discounts apply to how noticeable the effect is.  Two diamonds of the same quality, both with strong florescence may not have the same discount in price.

In all cases faint florescence has no impact on value because it is only noticeable in a laboratory setting and has no impact on brilliance.

What does Certified mean?

A certified diamond is a stone that has been submitted to a lab such as EGL, AGS, IGA or GIA for quality analysis.  The lab grades the color, clarity, in some cases and shapes cut, and takes detailed measurements of the diamond.

The importance of a certified diamond is to add value and for the consumer.  In comparing several diamonds of similar quality side by side the certificate can help the consumer to understand what he is paying for and why one diamond is more expensive than another.  The certificate also ads value because it shows another consumer or dealer a range of whee the diamond falls in quality. One should always shop with a diamond expert to point out the differences and allow you to chose which one is best for you.

Can You Compare Certified Diamonds From a Website?

Online retailers say “Yes” you can compare certified diamonds from a website. If there are 2 diamonds both 1.00ct, both G color, both SI1 and both Very Good Cut, they should be the same….correct?  My answer is if they are the same then why are they different prices?

If you take a list off any website and compare “like” diamonds you will see a range, and in some cases a very big range of prices.  Why is that?  I have been in the diamond business since the early 1990’s, before cut grades, before computer improvements in the grading process of diamonds, and before the internet.  I know without a shadow of a doubt that no 2 diamonds are the same. I don’t buy and  put a value on 2 diamonds with similar certificates the same because of this reason.
The intrinsic beauty and individualism of each diamond that was formed in the center of the earth some 100 billion years ago and brought to the surface through volcanic eruptions early in the earth’s history, cannot be judged by a grading certificate. Through my years of experience buying from sightholders, I have concluded that you must see the diamond, or even better a selection of diamonds,  in person to make an informed decision.

Do I Need to Buy a Diamond with a Certificate?

The easy answer to that is no.  Generally, diamonds with a rating of SI2 and higher are submitted to some lab for grading.  That does not mean that lower quality diamonds are not very attractive and not a great value. For those that want a great value and not concerned with looking at their diamond under a microscope or magnification and SI3 or I1 rated diamond may be the way to go.  This is probably the most popular quality sold because they can be nearly colorless – colorless, eye clean from inclusions and full of shine and sparkle!  I recommend to ask to see those first.

Can I Get a Non-Certified Diamond Insured?

Absolutely!  Houston Diamond Outlet offers a gemological insurance with every purchase, no matter the diamond you choose.  This includes the specifications of the diamond, but also includes a retail replacement value for insurance, which a certificate does not. So this appraisal is required by all insurance carriers and we are qualified and recognized by those carriers to issue our appraisals.

What Next?

Your next step is to browse our diamond database or simply contact one of our diamond experts.  Choosing the right diamond can be a confusing process.  Especially if you speak with an uneducated, or not experienced sales person.

Call us direct, toll free, and speak with one of our diamond experts.   We will ask you some basic questions to better understand your needs.  We can then suggest certain size, quality, or even shape to give you a head start on choosing a diamond. You can contact us by e-mail, chat, Facebook or phone, our diamond experts are available Monday – Friday 11am-5pm, or within 24 hours by email.  We will do our best to make this a pleasurable purchase and to find you the best diamond that fits your individual needs.

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